Topic 2a- Tissues, Organs and Organ Systems Flashcards Preview

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Flashcards in Topic 2a- Tissues, Organs and Organ Systems Deck (299):

What are large multicellular organisms made up of?

Why are multicellular organisms organised?

Large multicellular organ systems are made up of organ systems.

Multicellular organisms (like humans) can have millions of cells. To keep the organism going, those cells have to work together- which need organisation.


Define cells...

Cells are the BASIC BUILDING BLOCKS of all living organisms.


What are specialised cells?

Specialised cells carry out a PARTICULAR FUNCTION.


What is differentiation and when does it occur?

The PROCESS by which cells become specialised for a particular job is called DIFFERENTIATION.

Differentiation occurs during the DEVELOPMENT of a multicellular organism.


What do specialised cells form?

These specialised cells form TISSUES, which forms ORGANS, which form ORGAN SYSTEMS.


What types of systems do large multicellular organisms have?

LARGE MULTICELLULAR ORGANISMS (e.g. squirrels) have different SYSTEMS inside them for EXCHANGING and TRANSPORTING materials.

Example- Mammals have a breathing system-including airways and lungs. The breathing system is needed to take air into and out of the lungs, so that oxygen and carbon dioxide can be exchanged between the body and the environment.


How are similar cells organised?

Similar CELLS are organised into TISSUES.


what is the definition of a tissue?

A TISSUE is a GROUP of SIMILAR CELLS that work together to carry out a particular function. It can include MORE THAN ONE TYPE OF CELL.

On spec- A tissue is a group of cells with a SIMILAR STRUCTURE and FUNCTION.


How are tissues organised?

Tissues are organised into organ systems.


What is an organ?

An ORGAN is a group of DIFFERENT TISSUES (aggregations of tissues) that work together to perform a certain FUNCTION.


How are organs organised?

Organs are organised into ORGAN SYSTEMS.


What is an organ system?

An ORGAN SYSTEM is a GROUP OF ORGANISMS working together to form ORGANISMS.


What is the purpose of the lungs?

You need to get OXYGEN into your BLOODSTREAM to supply your CELLS for RESPIRATION. You also need to get rid of CARBON DIOXIDE from your blood.

This exchange of gases all happens inside your LUNGS. Air is forced in and out of your lungs by the action of breathing.


Where are the lungs located and what is the structure of lungs in mammals?

-The lungs are in the THORAX. The THORAx is th stop part of your body.

-It's separated from the lower part of the body by the DIAPHRAGM.

-The LUNGS are like big pink SPONGES and are protected by the RIBCAGE.
They're surrounded by the PLEURAL MEMBRANES.

-The air that you breathe in goes through the TRACHEA (windpipe). This splits into two tubes called BRONCHI (each one is a bronchus), one going to each lung.

-The bronchi split into progressively smaller tubes called BRONCHIOLES.

-The bronchioles finally end at small bags called ALVEOLI where the gas exchange takes place.


How do alveoli carry out gas exchange in the body?

1) The lungs contain millions and millions of little air sacs called ALVEOLI, surrounded by a NETWORK of BLOOD CAPILLARIES. This is where GAS EXCHANGE happens.

2) The BLOOD passing next to the alveoli has just returned to the lungs from the rest of the body, so it contains LOTS of CARBON DIOXIDE and VERY LITTLE OXYGEN. OXYGEN diffuses OUT of the ALVEOLUS (high concentration) and into the BLOOD (low concentration). CARBON DIOXIDE diffuses OUT of the BLOOD (high conc) into the alveolus (low conc) to be breathed out.

3) When the blood reaches body cells OXYGEN is released from the RED BLOOD CELLS (where there's a high concentration) and diffuses into the BODY CELLS (where there's a low concentration).

4) At the same time, CARBON DIOXIDE diffuses out of the BODY CELLS (where there's a high concentration) into the BLOOD (where there's a low concentration). It's then carried back to the LUNGS.


How are alveoli adapted for gas exchange?

The alveoli have:
1) An enormous surface area
2) A moist lining
3)Very thin walls
4) Good blood supply to maximise gas exchange
5) Ventilation (provides a steep concentration gradient)


How do you calculate the breathing rate?

Breaths per minute =
number of breaths ÷ number of minutes


How do you calculate heart rate?

You can calculate heart rate in beats per minute in the same was as breathing rate. Just replace the number of breaths with the number of beats.

heart rate= number of beats ÷ number of minutes


How do multicellular organisms like human transport materials between their cells?

Multicellular organisms need a way to transport materials between their cells. Humans (like many animals) have a transport system called the circulatory system to do this. The heart has a major role to play with it.


What is the function of the circulatory system?

The circulatory system's main function is to get FOOD and OXYGEN to every cell in the body.

As well as transporting things it is also a WASTE COLLECTION SERVICE- it carries CARBON DIOXIDE and UREA to where they can be removed from the body.


What does the circulatory system include?

The circulatory system includes:


What circulatory system do humans have?

Humans have a DOUBLE circulatory system- two circuits joined together.

Mammals have a double circulatory system.


What are the two circuits called?

-The pulmonary circulatory system
-The systemic circulatory system.


The human circulatory system is made up of two separate circuits. What is the function of each circuit?

-In the first circuit, the RIGHT VENTRICLE pumps DEOXYGENATED good to the LUNGS to take in OXYGEN. The blood then RETURNS to the heart.

-In the second circuit, the LEFT VENTRICLE pumps OXYGENATED blood around all the OTHER ORGANS of the BODY. The blood GIVES UP its oxygen at the body cells and the DEOXYGENATED blood RETURNS to the heart to be pumped out to the LUNGS again.


Describe the function of the heart...

The heart is an ORGAN that PUMPS blood around the BODY in a double circulatory system. The right ventricle pumps blood to theLUNGS where gas exchange takes place. The left ventricle pumps blood around the rest of the body.


What are the walls of the heart made from?

The heart is a pumping organ that keeps the blood flowing around the body.

-The walls of the heart are mostly made of MUSCLE TISSUE.


Why does the heart contain valves?

How many valves are in the heart?

What do the valves create?

The heart has valves to make sure that blood flows in the right direction- they prevent it flowing BACKWARDS.

There are 4 valves.

There are 2 between the atria and ventricles.
There are 2 at the base of the arteries leading from the ventricles.

The valves create a ONE WAY SYSTEM!


How many chambers does the heart have and what are they called?

The heart has four chambers; the RIGHT ATRIUM, RIGHT VENTRICLE, LEFT ATRIUM and LEFT VENTRICLE, which it uses to pump blood around.


What are the main blood vessels leading into and out of the chambers?

The main blood vessels leading into and out of theses chambers are:

1) Vena cava
2) Pulmonary artery
3) Aorta
4) Pulmonary vein


What is the function of coronary arteries?

The heart also needs its own supply of OXYGENATED blood. Arteries called CORONARY ARTERIES branch off the aorta and surround the heart, making sure that it gets all the OXYGENATED blood it needs.


Why are the coronary arteries vital in our health?

The coronary arteries are really important. If they become blocked, the heart can become starved of oxygen, potentially leading to a heart attack and heart failure.


How does the heart use its four chambers to pump blood around the body?


2) The ATRIA CONTRACT, forcing the blood into the VENTRICLES.

3) The VENTRICLES CONTRACT, forcing the blood into the PULMONARY ARTERY and the AORTA, and OUT of the HEART.

4) The pulmonary artery carries deoxygenated blood to the lungs. The aorta carries oxygenated blood to the tissues.

4) The blood then flows to the ORGANS through the ARTERIES, and RETURNS through VEINS.
Remember Arteries Away, Veins Towards.

5) The atria fill again and the whole cycle STARTS OVER.


How is your resting heart rate controlled?

How do these cells work?

-Your resting heart rate is controlled by a group of cells in the RIGHT ATRIUM wall that act as a PACEMAKER.

- These cells produce a small ELECTRIC IMPULSE which spreads to the surrounding muscle cells, causing them to CONTRACT.


What is heart rate?

Heart rate is the number of HEARTBEATS PER unit of TIME, e.g. the number of beats per minute (BPM).


What factors can lead to an increase or decrease in heart rate?

Some of the factors that may increase or decrease heart rate are;

-artificially (medicine)

- relaxed
-artificially (medicine)


What is an artificial pacemaker and when is it used?

An ARTIFICIAL PACEMAKER is often used to control the heartbeat if there are IRREGULARITIES as the natural pacemaker cells do't work properly (e.g. if the patient has an IRREGULAR HEARTBEAT). It's a little device that's implanted under the skin and a wire going to the heart. It produces an ELECTRIC CURRENT to keep the heart BEATING REGULARLY.


Is the blood in the heart at a low/high pressure?

-The blood flowing through left side (right atrium and ventricle) carries blood at a low pressure.

Whereas, the blood flowing through the right side (left atrium and ventricle) is at a high pressure.


What is the connection between muscle thickness in the heart and blood pressure?

The wall of the RIGHT VENTRICLE is LESS muscular than the left ventricle since it only needs to force the blood (at a low pressure) along the PULMONARY ARTERIES to the LUNGS.

The wall of the LEFT VENTRICLE- THICK and MUSCULAR since it must force blood through the ARTERIES to all the TISSUES of the body.

AORTA- The MAIN ARTERY of the body which carries oxygenated blood out to the TISSUES. Blood pressure is at its highest here in the aorta so the muscle is THICKER.


How many types of blood vessel are there?

There are 3 types of blood vessel, they transport the blood around our body.


What are the three blood vessels called?

The three different types of blood vessel are:

1) Arteries


What is the function of arteries?

Arteries are blood vessels which carry blood AWAY from the heart, towards the organs.


Explain how the structure of arteries are adapted to allow them to perform their function's?

1) The heart pumps blood out at HIGH PRESSURE so the artery walls are STRONG and ELASTIC.

They contain thick layers of MUSCLES to make them STRONG, and ELASTIC FIBRES to allow them to stretch and SPRING BACK.

2) The walls are THICK compared to the size of the hole down the middle (lumen).


Why is the blood carried by the arteries at high pressure?

Pressure is caused by the contractions of the heart cardiac muscle.


What do arteries branch into?

Arteries branch into CAPILLARIES.


What is the function of capillaries?

-Capillaries are involved in the EXCHANGE of materials at the TISSUES.

-They supply FOOD and OXYGEN, and take away WASTE like CO2.

-Capillaries carry blood REALLY CLOSE to EVERY CELL in the body to EXCHANGE SUBSTANCES with them.


Explain how the structure of capillaries are adapted to allow them to perform their function?

1)Capillaries are really TINY-to small to see.

2) They have PERMEABLE walls, so substances could diffuse in and out.

3) Their walls are usually ONLY ONE CELL THICK. This INCREASES the rate of diffusion by DECREASING the DISTANCE over which it occurs.

4) Capillaries are very NARROW. This gives them a LARGE SURFACE AREA compared to their VOLUME, which also increases the rate of diffusion.


What do capillaries eventually join?

Capillaries eventually JOIN UP to form VEINS.


What is the function of veins?

Veins carry blood towards the HEART.


At what pressure does blood travel through veins?

The blood is at LOWER PRESSURE in the veins so the walls don't need to be as THICK as artery walls.


Why is the blood travelling at a low pressure in the veins?

There is a reduced pressure as it has already carried carried the blood through the arteries and organs.


How are veins adapted to transport blood back to the heart?

1) Veins have a BIGGER LUMEN than arteries to help the blood FLOW despite the lower pressure.

2) They also have VALVES to help keep the blood flowing in the RIGHT DIRECTION.



How do you calculate the rate of blood flow?

rate of blood flow = volume of blood ÷ number of minutes


*Define blood?

*Blood is a tissue consisting of plasma, in which the red blood cells, white blood cells and platelets are suspended.


What is blood?

What is the function of blood?

Blood is a TISSUE- it's a group of similar cells which work together to perform a specific function.

The function of blood is to TRANSPORT substances (e.g. oxygen) around the body.


What does blood consist of?

It's made up of:

which are all suspended in a liquid called PLASMA.


What is plasma?

Plasma is a pale straw-coloured LIQUID which CARRIES JUST ABOUT EVERYTHING.


What does plasma carry?

It carries:
2) Nutrients like GLUCOSE and AMINO ACIDS.
3) CARBON DIOXIDE from the organs to the lungs.
4) UREA from the liver to the kidneys. (urea is a waste product produced from the breakdown of amino acids in the liver)
7) ANTIBODIES and ANTITOXINS produced by the white blood cells.


What is the function of red blood cells?

The job of red blood cells it to carry OXYGEN from the lungs to all the cells in the body.


Outline three ways in which red blood cells are adapted to carry oxygen...

1. They have a BICONCAVE DISC shape to give them a LARGE SURFACE AREA for absorbing OXYGEN.

2. They contain a red pigment called HAEMOGLOBIN, which carries OXYGEN.

3. They DON'T have a nucleus- this allows more room for haemoglobin, which means they can then carry MORE oxygen.


What is haemoglobin?

-Haemoglobin is a PROTEIN.


Describe the role of this red pigment in transporting oxygen...

All body cells need oxygen for respiration- a process which releases energy. Oxygen enters the blood when you breathe in, then red blood cells transport the oxygen from the lungs to all the cells in the body.

-As blood flows through the alveoli in the lungs, haemoglobin combines with oxygen to form oxyhemoglobin. When blood flows through RESPIRING tissues, oxyhemoglobin splits up into haemoglobin and oxygen. The oxygen that is released is used up by cells for RESPIRATION.

In the lungs: haemoglobin + oxygen ͢ oxyhaemoglobin

In respiring tissues:
oxyhemoglobin ͢ haemoglobin + oxygen


What is the function of white blood cells?

They defend against microorganisms that cause disease.


How do white blood cells defend against microorganisms?

They can do this in different ways:

-They can ENGULF unwelcome microorganisms (in a process called PHAGOCYTOSIS) and DIGEST them using enzymes.

-They can produce ANTIBODIES to fight microorganisms.

-They can produce ANTITOXINS to NEUTRALISE any toxins produced by the microorganisms.


True or false? White blood cells don't have a nucleus.

False. Unlike red blood cells, they do have a nucleus.


What are platelets?



Describe the purpose of platelets in blood.

They help the blood to CLOT (clump together) at a wound-this seals the wound to stop you from LOSING too much BLOOD.

It also stops MICROORGANISMS getting in at the wound.


What is the result of a lack of platelets?

A lack of platelets can cause excessive BLEEDING and BRUISING.


How do people adapt to live at high altitudes where there's less oxygen in the air?

The more red blood cells you've got the more oxygen can get to your cells. At high altitudes there's less oxygen in the air-so people who live their produce more red blood cells to compensate.


Do platelets contain a nucleus?

They have NO nucleus.


How does plasma help transport carbon dioxide?

Carbon dioxide is produced as a waste product of respiration. Carbon dioxide is transported in plasma from respiring cells to the alveoli in the lungs. As blood flows around the alveoli, carbon dioxide is removed from the blood by diffusion and then breathed out.


How does plasma help transport the products of digestion?

SOLUBLE SUGARS, AMINO ACIDS, FATTY ACIDS and GLYCEROL are produced as products of digestion in the small intestine. These soluble products are absorbed from the small intestine and transported in plasma to other body organs.


How does plasma help transport urea?

Urea is a waste product formed from EXCESS AMINO ACIDS. Urea is made in the liver and transported in blood plasma to the kidneys where it is removed from the body in urine.


What is meant by the term health?

*Health is the state of physical and mental well-being.


What is often the cause of ill health?

DISEASES, both communicable and non-communicable, are major causes of ill health. Other factors including DIET, STRESS and life SITUATIONS may have a profound effect on both physical and mental health.


Name the two types of disease.

Diseases can be communicable and non-communicable.


What are bacteria?

Bacteria are living cells and can multiply rapidly in favourable conditions. Once inside the body, they release poisons or toxins that can make us feel ill.


What are viruses?

Viruses are many times smaller than bacteria. They are among the smallest organisms known, consisting of a fragment of genetic material inside a protective protein coat.
Viruses can only reproduce inside host cells, damaging them when they do so. Once inside, they take over the cell and make hundreds of thousands of copies of themselves. Eventually, the virus copies fill the whole host cell and it bursts open. The viruses then pass out through the bloodstream, the airways, or by other routes.


What are pathogens?
What are the 2 main pathogens?

Pathogens are micro-organisms that cause infectious disease. Bacteria and viruses are the main pathogens.


What are communicable diseases?

What are the causes of communicable disease?

Communicable diseases are those that can SPREAD from PERSON TO PERSON or between ANIMALS and PEOLE.

They can be caused by things like BACTERIA, VIRUSES, PARASITES and FUNGI.


What are communicable diseases sometimes described as?

Give two examples of communicable diseases.

They're sometimes described as CONTAGIOUS or INFECTIOUS diseases.

MEASLES and MALARIA are examples of communicable diseases.


What are non-communicable diseases?

Non-communicable diseases are those that CANNOT SPREAD between people or between animals and people. They generally last for a LONG TIME and GET WORSE SLOWLY.


Give two examples of non-communicable diseases.

Asthma, cancer and coronary heart disease are examples of non-communicable disease.


Can diseases interact?

Sometimes diseases can INTERACT and cause OTHER physical and mental health issues that don't immediately seem related.


Name 4 diseases that can lead to other diseases...

*Different types of disease may interact.

• Defects in the IMMUNE SYSTEM mean that an individual is more likely to suffer from INFECTIOUS DISEASES.

• VIRUSES living in cells can be the trigger for CANCERS.

• IMMUNE REACTIONS initially caused by a pathogen can trigger ALLERGIES such as skin rashes and asthma.

• Severe PHYSICAL ILL HEALTH can lead to depression and other MENTAL ILLNESS.


Give 3 factors other than disease that can lead to ill health?

1)Whether or not you have a GOOOD BALANCED DIET that provides your body with EVERYTHING it needs, and in the RIGHT AMOUNTS. A poor diet can affect your physical and mental health.

2) The STRESS you are under- being constantly under lots of stress can lead to health issues.

3) Your LIFE SITUATION- for example, whether you have easy ACCESS to MEDICINE to treat lines, or ether you have ACCESS to things that can PREVENT you from getting ill in the first place, e.g. being able to buy HEALTHY FOOD or access CONDOMS to prevent the TRANSMISSION of some sexually transmitted diseases.


What physical health problems can stress cause?

Stress cause all sorts of physical health issues (e.g. high blood pressure, headaches and issues with the immune system) as well as mental health issues (e.g. depression).


Exam tip- in the exam, you may need to draw off a graph, or draw or explain tables, graphs and charts showing data on the incidence of disease.

What is the incidence of disease?

The incidence of disease is the number of new cases of the disease within a given time.

It may be given as e.g. the number of new cases per 100 00 persons per year, so make sure you know the units the data is shown in before answering the question.


Exam tip- in the exam you might need to identify a correlation between variables relating to disease incidence from a graph.

What is correlation?

Graphs are used to show the relationship between two variables. Data can show three different types of CORRELATION (relationship):

Positive correlation e.g. ⟋ -As one variable increases the other increases.

Inverse (negative) correlation e.g. ⟍ -As one variable increases the other decreases.

No correlation on a graph shows scattered results.


Exam tip- sampling is often used when collecting data related to health and patterns in diseases.

What is epidemiological data?

Why is sampling used when collecting epidemiological data?

-Epidemiological data is data related to health and patterns in diseases.

-Sampling is often used when collecting epidemiological data. This is because it would take too long and cost too much to collet data from the entire population.


What is cardiovascular disease?

Cardiovascular disease is a term used to describe diseases of the heart or blood vessels.


What is coronary heart disease?

Coronary heart disease is when the CORONARY ARTERIES that supply the BLOOD to the heart muscle get BLOCKED by LAYERS OF FATTY MATERIAL BUILDING UP. This causes the arteries to become NARROW, so blood flow is RESTRICTED and there's a LACK OF OXYGEN to the heart muscle- this can result in a HEART ATTACK.


What is used to treat coronary heart disease?

Stents can be used to treat coronary heart disease.


What is a stent?

What is the role of a stent?

Stents are wire mesh TUBES that can be inserted INSIDE ARTERIES.

They are used to WIDEN the arteries and keep them OPEN. This makes sure BLOOD CAN PASS THROUGH to the heart muscles. This keeps the person's HEART BEATING (and the person alive).


Describe how stents can be used to treat people with coronary heart disease.

They can be inserted into the coronary arteries to make sure blood can pass through to the heart muscles. This keeps the person's heart beating and keeps the person alive.


How are stents inserted into arteries?

-To insert a stent, a CATHETER is inserted into a blood vessel in the leg or wrist.

-The catheter contains a balloon and a metal stent.

-It is directed to the coronary artery and when the narrowed section of artery is found, the balloon is inflated which causes the stent to expand, and it becomes lodged in the artery.

-The stent then acts to keep the artery open so that the heart continues to receive enough oxygen to function effectively.


What are the advantages of using stents to treat patients with CHD?

1) Stents are a way of LOWERING the risk of a HEART ATTACK in people with coronary heart disease.

2) They are EFFECTIVE for a LONG TIME and the RECOVERY TIME from the surgery is relatively QUICK.

3) Stents are good alternatives to more risky operations, like BY-PASS SURGERY, providing the patient's heart disease is not too serious.


What are the disadvantages of using stents to treat patients with CHD?

- There is a risk of COMPLICATIONS during the operation (e.g. heart attack) and a risk of INFECTION from the surgery. There is also the risk of patients developing a BLOOD CLOT near the stent. This is called THROMBOSIS.

-Fatty deposits may build up on the stent over time- meaning that blood flow to the heart muscle may be reduced again.


What is cholesterol?

Cholesterol s an essential lipid that your body produces and needs t function properly.


Is cholesterol bad for your health?

What is the bad cholesterol called?

Too much of a certain type of CHOLESTEROL can cause HEALTH PROBLEMS.

Bad cholesterol is called LDL cholesterol.


What health problems are caused by having too much LDL cholesterol?

Having too much of this 'bad' cholesterol in the bloodstream can cause FATTY DEPOSITS to form inside ARTERIES, which can lead to CORONARY HEART DISEASE.


What are statins?

Statins are DRUGS that are WIDELY USED and can reduce the amount of 'bad' cholesterol PRESENT in the BLOODSTREAM. This SLOWS DOWN the rate of fatty acids forming.


What are the advantages of using statins?

1) By reducing the amount of 'bad' cholesterol in the blood, statins can REDUCE the risk of STROKES, CHD and HEART ATTACKS.

2) As well as reducing the amount of 'bad' cholesterol, statins can INCREASE the amount of a BENEFICIAL type of cholesterol (known as 'GOOD' or HDL cholesterol) in your bloodstream. This type can REMOVE 'bad' cholesterol from the blood.

3) Some studies suggest that statins may also help PREVENT some OTHER DISEASES.


What are the disadvantages of using statins?

1) Statins are a LONG-TERM drug that must be taken REGULARLY. There's the risk that someone could FORGET to take them.

2) Statins can sometimes cause NEGATIVE SIDE EFFECTS, e.g. headaches. Some of these side effects can be SERIOUS, e.g. kidney failure, liver damage and memory loss.

3) The effect of the statins ISN'T INSTANT. It takes TIME for their EFFECT to kick in.


When are donor hearts transplanted?

If a patient has HEART FAILURE, doctors may perform a HEART TRANSPLANT (or HEART AND LUNGS TRANSPLANT if the LUNGS are also DISEASED) using DONOR ORGANS from people who have recently died.


What are artificial hearts?

ARTIFICIAL HEARTS are MECHANICAL DEVICES that PUMP BLOOD for a person whose own heart has FAILED.


When are artificial hearts used?

They are occasionally used as a temporary fix, to keep a person alive until a donor heart can be found or to help a person recover by allowing the heart to rest and heal. In some cases though they are used as a permanent fix, which reduces the need for a donor heart.


What are the advantages of using an artificial heart?

1) The main advantage of artificial hearts is that they're LESS LIKELY TO BE REJECTED by the body's immune system than a donor heart. This is because they're made from METALS (titanium) or PLASTICS, so the body doesn't recognise them as 'FOREIGN' and attack in the same way as it does with living tissue.

2) Used as a short term measure to keep patients alive until a biological donor heart can be found.


What are the disadvantages of using an artificial heart?

Surgery to fit an artificial heart (as with transplant surgery) can lead to BLEEDING and INFECTION. Also artificial hearts DON'T work as well as healthy NATURAL ones- parts of the heart could WEAR OUT or the ELECTRICAL MOTOR could FAIL. Blood doesn't flow through artificial hearts as SMOOTHLY, which can cause BLOOD CLOTS and lead to STROKES. A patient receiving an artificial heart has to take DRUGS to THIN their blood and make sure CLOTS don't occur. This can cause problems with bleeding if they're HURT in an accident because their blood can't clot normally to heal the wounds.


How can heart valves become damaged?

The VALVES in the heart can be damaged or weakened by HEART ATTACKS, INFECTION or OLD AGE.


What does damage to a heart valve cause?

The damage may cause the VALVE TISSUE to STIFFEN, so it WON'T OPEN PROPERLY. Or a valve may become LEAKY, allowing blood to flow in BOTH DIRECTIONS rather than just forward. This means that blood DOESN'T CIRCULATE as EFFECTIVELY as normal.


How is severe valve damage treated?

Severe valve damage can be treated by REPLACING the valve.


What two types of replacement valve are used to treat damaged valves?

Replacement valves can be ones taken from HUMANS or OTHER MAMMALS (e.g. cows or pigs)- these are BIOLOGICAL VALVES. Or they can be MAN-MADE- these are MECHANICAL VALVES.


What are the advantages of using biological valves?

1) They do not damage RED BLOOD CELLS as they pass through the open valves.


What are the advantages of using mechanical valves?

1) Very STRONG and DURABLE- able to last a lifetime.


What are the disadvantages of using biological valves?

1) Prone to becoming HARDENED over the course of several years.

2) For patient with long life expectancy, there is a higher chance of further operations to replace the valves (any operation carries risks).


What are the disadvantages of using mechanical valves?

1) Damage red blood cells as they pass through the open valves.

2) Require the patient to take anti-blood clotting drugs for the rest of their life.

3) Some people say they can hear the valves opening and closing.



A BLOOD PRODUCT is any component of the BLOOD which is collected from a donor for use in a BLOOD TRANSFUSION.


What do most blood products used in medicine consist of?

WHOLE BLOD is uncommonly used in TRANSFUSION MEDICINE at present; most blood products consist of specific processed components such as RED BLOOD CELLS, BLOOD PLASMA, OR PLATELETS.


What do blood products used in blood transfusions rely upon?

It relies on people being willing to donate their blood.


What steps must be taken to ensure donated blood is safe to transfuse?

Blood has to be screened/checked for risk of INFECTION.


Why can blood products be rejected by the body?

Blood products be rejected by the body if it is the wrong 'blood type'.


What is artificial blood?

Artificial blood is a BLOOD SUBSTITUTE, e.g. a salt solution (saline), which is used to REPLACE the LOST VOLUME of blood.


When is artificial blood used?

When someone LOSES A LOT OF BLOOD, e.g. in an accident, their heart can still PUMP the remaining RED BLOOD CELLS around (to get enough OXYGEN to their ORGANS), as long as the VOLUME of their blood can be TOPPED UP.


How is artificial blood kept safe?

It's safe (if no AIR BUBBLES get into the blood).


Why is artificial blood used?

It can keep people alive even if they lose 2/3 of their red blood cells. This may give the patient enough TIME to produce NEW blood cells. If not, the patient will need a BLOOD TRANSFUSION.


What would artificial blood ideally replace?

Ideally, an artificial blood product would REPLACE the function of the lost RED BLOOD CELLS, so that there's NO NEED for a blood transfusion. Scientists are currently working on products that can do this.


What are risk factors?

Risk factors are things that are linked to an INCREASE in the LIKELIHOOD that a person will develop a certain disease during their lifetime. They DON'T GUARANTEE that someone WILL get the disease.


What can risk factors be?

Risk factors are linked to an increased rate of a disease.
They can be:
• aspects of a person’s lifestyle
• substances in the person’s body or environment.


Explain how a person's lifestyle/ substances in the person's body or environment can be a risk factor for getting a disease.

Often aspects of a person's LIFESTYLE (e.g. how much exercise they do).

Risk factors can also be the presence of certain substances in the environment (e.g. air pollution) or SUBSTANCES in your body (e.g. asbestos fibres-asbestos was a material used in buildings until it was realised that the fibres could build up in your airways and cause disease such as cancer in later life).


What can cause non-communicable diseases?

*Many NON-COMMUNICABLE diseases are caused by a number of different risk factors INTERACTING with each other rather than one factor alone.


Can lifestyle factors affect how common a disease is at a local, national and global level?

Lifestyle factors can have different impacts LOCALLY, NATIONALLY and GLOBALLY.

E.g. in DEVELOPED COUNTRIES, non-communicable diseases are MORE COMMON as people generally have a HIGHER INCOME and can buy HIGH-FAT food.

NATIONALLY, people from DEPRIVED AREAS are MORE LIKELY to smoke, have a poor diet and not exercise. This means the incidence of CARDIOVASCULAR DISEASE, OBESITY and TYPE 2 DIABETES is HIGHER in those areas. Your INDIVIDUAL CHOICES affect the LOCAL incidence of disease.


*What are the 6 risk factors that can cause a disease directly?

• The effects of diet, smoking and exercise on cardiovascular disease.
• Obesity as a risk factor for Type 2 diabetes.
• The effect of alcohol on the liver and brain function.
• The effect of smoking on lung disease and lung cancer.
• The effects of smoking and alcohol on unborn babies.
• Carcinogens, including ionising radiation, as risk factors in cancer.


Give two diseases that smoking has been proven to cause.

How does smoking damage the lungs and arteries?

SMOKING has been proven to directly cause CARDIOVASCULAR DISEASE, LUNG DISEASE and LUNG CANCER. It damages the WALLS of ARTERIES and the CELLS in the LINING of the LUNGS.


Name the disease that is caused by obesity.

Explain how this occurs.

It's thought that OBESITY can directly cause TYPE 2 DIABETES by making the body less SENSITIVE or RESISTANT to insulin, meaning that it struggles to CONTROL the CONCENTRATION of GLUCOSE in the blood.


Give two health problems that excessive alcohol consumption has been proven to cause.

-Drinking TOO MUCH ALCOHOL has been shown to cause LIVER DISEASE.

The liver breaks down alcohol, but the reaction can damage its cells.
Liver cells may also be damaged when toxic chemicals leak from the gut due to damage to the intestines caused by alcohol.

-Too much alcohol can affect BRAIN FUNCTION too.

It can DAMAGE the NERVE CELLS in the brain, causing the brain to LOSE VOLUME.


How can smoking and consuming alcohol when pregnant affect the unborn baby?

-SMOKING when pregnant can cause LOTS of HEALTH PROBLEMS for the UNBORN BABY.

Smoking when pregnant reduces the amount of oxygen the baby receives in the womb and can cause lots of health problems for the unborn baby.

-Drinking ALCOHOL has similar effects.

Alcohol can damage the baby's cells, affecting its development and causing a wide range of health issues.


What is a carcinogen?

A carcinogen are things that are known to CAUSE CANCER.


Give an example of a carcinogen.

Cancer can be directly caused by EXPOSURE to certain SUBSTANCES or RADIATION.

IONISING RADIATION (e.g. from X-rays) is an example of a CARCINOGEN.


What is a correlation?

Graphs are used to show the relationship between two variables. Data can show 3 different types of correlation (relationship):

1) POSITIVE correlation- as one variable increases the other variable increases.

2) INVERSE (negative) correlation- as one variable INCREASES the other DECREASES.

3) No correlation- there' no relationship between the two variables.


How are risk factors identified?

Risk factors are identified by scientists looking for CORRELATIONS in data, and CORRELATION DOESN'T ALWAYS EQUAL CAUSE.

Some risk factors aren't directly capable of causing a disease.


Give an example of a positive correlation, where the risk factor does not directly cause the disease.

For example, a LACK OF EXERCISE and a HIGH FAT DIET are heavily linked to an increased chance of CARDIOVASCULAR DISEASE, but they can't cause the disease directly.

It's the resulting HIGH BLOOD PRESSURE and HIGH 'BAD' CHOLESTEROL LEVELS that can actually CAUSE it.


What is the human cost of non-communicable diseases?

The HUMAN cost of non-communicable disease is obvious. TENS OF MILLIONS of people around the world die from non-communicable diseases per year. People with these diseases may have a LOWER QUALITY OF LIFE or a SHORTER LIFESPAN. This not only affects the SUFFERERS themselves, but their LOVED ONES too.


What is the financial cost of non-communicable diseases?

It's also important to think of the FINANCIAL cost. The cost to the NHS of RESEARCHING and TREATING these diseases is HUGE- and it's the same for other health services and organisations around the world.

FAMILIES may have to MOVE or ADAPT THEIR HOME to help a family member with a disease, which can be costly.
Also if the family member with the disease has to GIVE UP WORK or DIES, the family's INCOME will be REDUCED.

A REDUCTION in the number of people ABLE TO WORK can also effect a COUNTRY'S ECONOMY.


Why is sampling used for collecting disease risk data?

To save time and money, scientists often use sampling when collecting data on risk factors for diseases rather than collecting data from the entire population.


What is cancer caused by?

Cancer is caused by UNCONTROLLED cell growth and division. This uncontrolled growth and division is a result of CHANGES that occur to the cells and results in the formation of a TUMOUR.


What is a tumour?

A tumour is a growth of abnormal cells.


What are the two types of tumour?

Not all tumours are cancerous.
They can be BENIGN or MALIGNANT.


What are benign tumours?

Benign- this is where the tumour grows until there's no more room. The tumour STAYS in one place (usually within a membrane) rather than invading other tissues in the body. This type ISN'T normally dangerous, and the tumour is NOT cancerous.


Describe the characteristics of malignant tumours?

Malignant- this is where the tumour grows and SPREADS to neighbouring healthy tissues. Cells can BREAK OFF and spread to other parts of the body by travelling in the BLOODSTREAM. The malignant cells then INVADE healthy tissues elsewhere in the body and form SECONDARY TUMOURS. Malignant tumours are DANGEROUS and can be fatal- THEY ARE CANCEROUS.


Can anyone develop cancer?

Are cancer survival rates increasing or decreasing and why?

Anyone can develop cancer.

Cancer survival rates have INCREASED due to medical advances such as IMPROVED TREATMENT, being able to DIAGNOSE cancer EARLIER and INCREASED SCREENING for the disease.


Do risk factors of cancer mean that you will definitely get cancer?

Having risk factors does NOT mean that you will definitely get cancer. However, risk factors can INCREASE the chance of developing some cancers. It just means that you're at an increased risk of developing the disease compared to some people who have fewer risk factors, or don't have any risk factors at all.


What are risk factors of cancer associated with?

Some risk factors are associated with aspects of a person's LIFESTYLE, and some are associated with GENETICS.


What are the 4 risk factors of cancer associated with a person's lifestyle?

1) SMOKING- it's a well known that smoking is linked to LUNG CANCER, but research has also linked it to OTHER TYPES of cancer too, including mouth, bowel, stomach and cervical cancer.

2) OBESITY- obesity has been linked to MANY DIFFERENT CANCERS, including bowel, liver and kidney cancer. It's the SECOND BIGGEST preventable cause of cancer after smoking.

3) UV EXPOSURE- People who are often exposed to UV RADIATION from the sun have an increased chance of developing SKIN CANCER. People who live in SUNNY CLIMATES and people who pend a lot of time OUTSIDE are at a HIGHER RISK of the disease. People who frequently use SUN BEDS are also putting themselves at a higher risk of developing skin cancer.

4) VIRAL INFECTION- Infection with some viruses has been shown to INCREASE the chances of developing CERTAIN TYPES of cancer. For example, infection with HEPATITIS B and HEPATITIS C viruses can increase the risk of developing LIVER CANCER. The likelihood of becoming infected with these viruses sometimes depends on lifestyle- e.g. they can be spread between people through UNPROTECTED SEX or SHARING NEEDLES.


What are genetic risk factors of cancer?

Genes control the activities of your cells and your characteristics. The genes you have are inherited from your parents.

Sometimes you can INHERIT FAULTY GENES that make you MORE SUSCEPTIBLE to cancer.

Example: Mutations (changes) in the BRCA genes have been linked to an INCREASE of developing BREAST and OVARIAN CANCER.


How are plant cells organised?

Plants are made of ORGANS like STEMS, ROOTS and LEAVES. Plant organs work together to make ORGAN SYSTEMS. These can perform the various tasks that a plant needs to carry out to survive and grow- for example TRANSPORTING SUBSTANCES around the plant. Plant organs are made of TISSUES.


What are the 3 organs in a plant?

What do they form, and what is there function?

The ROOTS, STEM and LEAVES are organs and work together in an ORGAN SYSTEM that TRANSPORTS substances around the body.


Plant organs are made of tissues.
What are the 5 tissues called?
What are the function of these tissues?

1) Epidermal tissue- this COVERS the whole plant.

2) Palisade mesophyll tissue- this is the part of the leaf where most PHOTOSYNTHESIS happens.

3) Spongy mesophyll tissue- this is also in the leaf, and contains big AIR SPACES to allow GASES to DIFFUSE in and out of cells.

4) Xylem and Phloem- they TRANSPORT things like WATER, MINERAL IONS and FOOD around the plant (through the roots, stems and leaves).

5) Meristem tissue- this is found at the GROWING TIPS of SHOOTS and ROOTS and is able to DIFFERENTIATE (change) into lots of DIFFERENT TYPES of plant cell, allowing the plant to GROW.


How are the structures of the tissue in leaves adapted to allow them to perform their function?

1) The epidermal tissues are covered with a WAXY CUTICLE, which helps to REDUCE WATER LOSS by evaporation.

2) The upper epidermis is TRANSPARENT so that light can pass through it to the PALISADE LAYER.

3) The palisade layer has lots of CHLOROPLASTS (the little structures where photosynthesis takes place). This means that they're near the top of a leaf where they can get the most LIGHT.

4) The XYLEM and PHLOEM form a network of vascular bundles, which DELIVER WATER and other NUTRIENTS to the entire leaf and take away the GLUCOSE produced by photosynthesis. They also help SUPPORT the structure.

5)The tissues of leaves are also adapted for EFFICIENT GAS EXCHANGE. E.g. the LOWER EPIDERMIS is full of little holes called STOMATA, which let CO2 diffuse directly into the leaf. The opening and closing of stomata is controlled by GUARD CELLS in response to environmental conditions. The AIR SPACES in the SPONGY MESOPHYLL tissue INCREASE the rate of diffusion of gases.


What is the structure of tissue in a leaf?

1) At the top is the WAXY CUTICLE.
2) Then there is the PALISADE MESOPHYLL tissue.
3) Then there is the SPONGY MESOPHYLL tissue.
4) At the bottom is EPIDERMAL TISSUE.

EXAM TIP: If you're struggling to remember the structure just think of it as Epidermis is External and MESOPHYLL is in the MIDDLE.


Name the plant tissue where photosynthesis occurs.

Palisade mesophyll tissue.


What is the function of the air spaces in spongy mesophyll tissue?

They allow gases to diffuse in and out of cells.


Where in a plant is meristem found?

In the growing tips of shoots and roots.


Explain why the upper epidermis of a leaf is transparent.

So that light can pass through to the palisade layer, which contains lots of chloroplasts for photosynthesis.


How do flowering plants transport substances around?

Flowering plants have two separate types of tissue- phloem and xylem- for transporting substances around. Both types of tissue form 'tubes', which go to every part of the plant, but they are totally separate.


What is transported in phloem tubes?

Where is it transported to?

what is this process of transporting ------called?

-Phloem tubes transport FOOD SUBSTANCES (mainly dissolved sugars) made in the leaves to the rest of the plant for IMMEDIATE USE (e.g. in growing regions) or for STORAGE.

-The transport goes in BOTH DIRECTIONS- from the leaves down to the roots, and from the roots up to the leaves.

- This process is called TRANSLOCATION.


Define translocation.

The movement of dissolved sugars around a plant.


What is the structure of phloem tubes?

- Phloem tubes are made of columns of ELONGATED living cells with small PORES in the END WALLS to allow CELL SAP to flow through.


What is cell sap?

Cell sap is a liquid that's made up of the substances being transported and water.


Give two substances that are transported in xylem tubes?

Xylem tubes carry WATER and MINERAL IONS.


Where do xylem tubes transport water and mineral ions to?

Xylem tubes carry water and mineral ions up the plant - from the ROOTS, to the STEM and LEAVES.


What is the process of transporting water and mineral ions through xylem tubes called?

The movement of water from the ROOTS, THROUGH the XYLEM and OUT of the LEAVES is called the TRANSPIRATION STREAM.


What is the structure of xylem tubes?

Xylem tubes are made of DEAD CELLS joined end to end with NO end walls between them and a hole down the middle.

They're strengthened with a material called LIGNIN.


What is transpiration?

Transpiration is the loss of water from a plant.


Define transpiration stream.

The movement of water from a plant's roots, through their xylem and out of the leaves.


What is the cause of transpiration?

Transpiration is caused by the EVAPORATION and DIFFUSION of water from a plant's surface.


Where does most transpiration occur?

Most transpiration occurs at the LEAVES.


Explain how water is transported from the roots of a plant to its leaves.

1)Water from inside a leaf EVAPORATES and DIFFUSES out of the leaf, mainly through the STOMATA (tiny holes found mainly on the lower surface of the leaf.

2) This creates a slight SHORTAGE of water in the leaf, and so more water is drawn up from the rest of the plant through the XYLEM vessels, to replace it.

3) This in turn means MORE water is drawn UP from the ROOTS, and so there's a CONSTANT transpiration stream of water through the plant


Which area of a plant do the phloem tubes transport substances from?

Water is transported up a plant the transpiration stream. Water escapes from the leaves by evaporation and diffusion. This creates a slight shortage of water in their leaves, which causes more water to be drawn up the xylem and into the leaves. This in turn causes more water to be drawn up the xylem from the roots.

Remember, the transpiration stream only goes on in the xylem-it does not involve the phloem.


How are leaves adapted for photosynthesis?

Transpiration is just a side-effect of the way leaves are adapted for PHOTOSYNTHESIS. They have to have stomata in them so that gases can be exchanged easily. Because there's more water inside the plant than in the air outside, the water escapes from the leaves through the stomata by diffusion.


What is the effect of light intensity on the rate of transpiration?

LIGHT INTENSITY-The brighter the light, the greater the transpiration rate. STOMATA begin to CLOSE as it gets darker. Photosynthesis can't happen in the dark, so they don't need to be open to let CO2 in. When the stomata are closed, very little water can escape.


What is the effect of temperature on the rate of transpiration?

TEMPERATURE- the WARMER it is, the FASTER transpiration happens. When it's warm the water particles have MORE ENERGY to evaporate and diffuse out of the stomata.


What is the effect of air flow on the rate of transpiration?

AIR FLOW- the BETTER the air flow around a leaf (e.g. stronger winds), the GREATER the transpiration rate. If air flow around a leaf is POOR, the water vapour just SURROUNDS THE LEAF and doesn't move away. This means there's a HIGH CONCENTRATION of water particles outside the leaf as well as inside it, so DIFFUSION doesn't happen as quickly. If there's GOOD air flow, the water vapour is SWEPT AWAY, maintaining a LOW CONCENTRATION of water in the air outside the leaf. Diffusion then happens quickly from an area of higher concentration to an area of lower concentration.


What is the effect of humidity on the rate of transpiration?

HUMIDITY- the DRIER the air around a leaf, the FASTER transpiration happen. This is like what happens with air flow. If the air is HUMID there's a lot of water in it already, so there's not much of a DIFFERENCE between the inside and the outside of the leaf. Diffusion happens FASTEST if there's a REALLY HIGH CONCENTRATION in one place, and a REALLY LOW CONCENTRATION in the other.

Tip- wet clothes dry as water evaporates from the fabric. You wouldn't expect clothes hung out in the garden to dry very quickly on a cold, wet day-so don't expect evaporation from a plant to be quick under those conditions either.


How can you estimate the rate of transpiration?

You can estimate the rate of transpiration by measuring the UPTAKE OF WATER by ta plant. This is because you can assume that wWATER UPTAKE by the plant is directly related to WATER LOSS by the leaves (transpiration).

Set up the apparatus e.g. the POTOMETER as in the diagram on page 44, and then record the STARTING POSITION of the air bubble. Start a stopwatch and record the DISTANCE MOVED by the bubble per unit time, and record the DISTANCE MOVED by the bubble per unit time, e.g. per hour. Keep the CONDITIONS CONSTANT throughout the experiment, e.g. the TEMPERATURE and AIR HUMIDITY.


Potometers can be used to estimate the rate of transpiration. What does a potometer actually measure?

The uptake of water by a plant.


How do you calculate the rate of transpiration?

You can use the data you collect in your experiment to calculate the rate of transpiration. Take a look at this example:

A potometer was set up to measure the rate of transpiration of a plant. In 60 minutes, the bubble i the photometer moved 6.6 cm. Calculate the rate of transpiration. Give your answer in mm/min.

1. First convert 6.6 cm into mm:

6.6 x 10 = 66 mm

2. Then divide the distance moved by the time taken:

66 ÷ 60 = 1.1 mm/min


What is the structure of a stoma?

A stoma is a tiny opening on a plant leaf, but there are specialized cells surrounding each stoma that control how open or closed it is. These specialized cells are called guard cells, and they are triggered by a number of factors, such as sunlight, humidity, temperature


Name the cells that control the size of the stomata.

Define this cell...

Guard cells.

Guard cell- a cell found on either side of a stoma, which controls the stoma's size.


What is the function of stomata?

CO2 can enter through stoma (hole), and photosynthesis can occur; also allows gases and water molecules to go in and out of leaf.


What is the structure of guard cells?

Two guard cells surround EACH stoma They have a kidney shape which OPENS and CLOSES the STOMATA in a leaf.


When do stomata open and close?

1) When the plant has LOTS of water the guard cells fill with it and go plump and TURGID. This makes the stomata OPEN so GASES can be exchanged for PHOTOSYNTHESIS.

2) When the plant is SHORT of water, the guard cells lose water and become FLACID making the stomata CLOSE. This helps stop too much water vapour ESCAPING.

3) THIN outer walls and THICKENED inner walls make the opening and closing work.

4) There also SENSITIVE TO LIGHT and upper close at night to save water without losing out on photosynthesis.

5) You usually find MORE stomata on the UNDERSIDES of leaves vs on top. The LOWER SURFACE is SHADED and COOLER - so LESS WATER is LOST through the stomata than if they were on the UPPER SURFACE.

6) Guard cells are therefore adapted for GAS EXCHANGE and CONTROLLING WATER LOSS within a LEAF.


*How are root hair cells adapted?

*Root hair cells are adapted for the efficient uptake of water by osmosis, and mineral ions by active transport.


*What is the role of stomata and guard cells?

*The role of stomata and guard cells are to control gas exchange and water loss.


How does cell sap move through xylem tubes?

Phloem is composed of tubes of elongated cells. Cell sap can move from one phloem cell to the next through PORES in the end walls.


Why is it important to be able to control the rate at which chemical reactions are taking place?

Living things have thousands of different CHEMICAL REACTIONS going on inside them all the time, including the reactions involved in metabolism.

These reactions need to be CAREFULLY CONTROLLED-to get the RIGHT amounts of substances.


How can you increase the rate of a reaction?

What are the problems with this?

You can usually make a reaction happen more quickly by RAISING the TEMPERATURE.

This would speed up the useful reactions but also the unwanted ones too... not good. There's also a limit to how far you can raise the temperature inside a living creature before its CELLS start getting DAMAGED.


Other than increasing temperature how else can living things increase the rate of reactions?

Living things can produce ENZYMES that act as BIOLOGICAL CATALYSTS.


What are the functions of enzymes?

Enzymes act as biological catalysts. Enzymes reduce the need for high temperatures and we ONLY have enzymes to speed up the USEFUL CHEMICAL REACTIONS in the body.


Define a catalyst.

A CATALYST is a substance which INCREASES the speed of a reaction, without being CHANGED or USED UP in the reaction.


What are the characteristics/structure of enzymes?

Enzymes are all LARGE PROTEINS and all proteins are made up of CHAINS of AMINO ACIDS. These chains are folded into UNIQUE SHAPES, which enzymes need to do their job.


What do chemical reactions involve?

Chemical reactions usually involve things either being SPLIT APART or JOINED TOGETHER.


What does the lock and key model of enzyme action tell us?

EVERY enzyme has an ACTIVE SITE with a unique shape that FITS onto the substance involved in a reaction.

Enzymes are really PICKY- they usually only catalyse ONE SPECIFIC REACTION.

This is because, for the enzyme to work, the substrate has to FIT into its active site. If the substrate doesn't MATCH the enzyme's active site, then the reaction WON'T be catalysed.


What does the lock and key model not show?

The lock and key model of enzyme action is a simplified model. This is SIMPLER than how enzymes actually work. In reality, the active site CHANGES SHAPE a little as the substrate binds to it to get a TIGHTER FIT. This is called the 'INDUCED FIT' model of enzyme action.


What two factors change the rate of an enzyme-catalysed reaction?

Changing the TEMPERATURE and pH changes the RATE of an enzyme-catalysed reaction.


Describe what happens when the temperature is increased on the rate of an enzyme-catalysed reaction and why?

-Like with any reaction, a higher temperature INCREASES the rate at first. (This is because as the temp increases, the enzyme and substrate are MOVING FASTER so there are more COLLISIONS PER SECOND between the substrate and the active site.)


What is the optimum temperature?

At a certain temperature, the enzyme is working at the FASTEST POSSIBLE RATE. That's called the OPTIMUM TEMPERATURE.

At this point, there is the MAXIMUM FREQUENCY of successful COLLISIONS between the substrate and the active site.


What is the optimum temperature for enzymes?

The optimum temperature for MOST HUMAN enzymes is around 37℃. This is human body temperature.


What happens to the enzyme once the temperature exceeds the optimum temperature and why?

-As we increase the temperature PAST THE OPTIMUM, then the activity of the enzyme rapidly DECREASES to ZERO.

-When it gets TOO HOT, some of the BONDS holding the enzyme together BREAK. This changes the shape of the enzymes's ACTIVE SITE.


So the substrate WON'T FIT anymore.

The enzyme/active site is said to be DENATURED. This means the enzyme can NO LONGER CATALYSE the reaction.


What is the optimum temperature for enzymes?

Enzymes have a temperature at which they are most active- this is called the optimum temperature.

All enzymes have have an OPTIMUM TEMPERATURE that they work best at.

Enzymes in the human body normally work best at around 37℃.


Other than temperature, what else changes the rate of an enzyme-catalysed reaction and how?

Th pH also affects enzymes.

If it's TOO HIGH (too alkaline) or TOO LOW (too acidic), the pH interferes with the BONDS holding the enzyme together.

This changes the SHAPE of the ACTIVE SITE and DENATURES the enzyme.


What is the optimum pH for enzymes?

All enzymes have an optimum pH that they work best at- this is called the optimum pH.

The optimum pH is different for different enzymes depending on where they work. For many enzymes it's neutral pH, but not always.


Give an example of an enzyme which doesn't have an optimum pH of 7.

For example, PEPSIN is an enzyme used to break down PROTEINS in the STOMACH. It works best at pH 2, which means it's well suited to the acidic conditions in the stomach.


Why can enzymes be described as biological catalysts?

Because they increase the speed of a biological reaction without being changed or used up in the reaction.


What is the name of the part of an enzyme that binds to the substrate?

Active site.


What enzyme catalyses the breakdown of starch?

The enzyme AMYLASE catalyses the breakdown of STARCH.


What are the products from the breakdown of starch using amylase?

Amylase breaks down starch to MALTOSE (simple sugars).


How can you detect the presence of starch in a substance?

You can detect starch using IODINE SOLUTION.


What is the original colour of iodine solution?

What colour does it change to if starch is present?

Iodine solution is a BROWNY-ORANGE colour.

If starch is present, the iodine solution will change to BLUE-BLACK.


How can you investigate how pH affects amylase activity?

1. Put a DROP of iodine solution into every well on a SPOTTING TILE.

2. Place a BUNSEN BURNER on a HEAT-PROOF MAT, and a TRIPOD and GAUZE over the bunsen burner. put a beaker of WATER on top of the tripod and HEAT the water until it is 35℃ (use a THERMOMETER to measure the temp). Try to keep the temp of the water CONSTANT throughout the experiment.

3. Use a SYRING to add 1㎤ of AMYLASE SOLUTION and 1 ㎤ of a BUFFER SOLUTION with a pH of 5 to a boiling tube. Using TEST TUBE HOLDERS, put the tube into the beaker of water and wait for five minutes.

4. Next, use a DIFFERENT SYRINGE to add 5㎤ of a STARCH SOLUTION to the boiling tube.

5. Immediately MIX THE CONTENTS of the boiling tube and start a STOP CLOCK.

6. Use CONTINUOUS SAMPLING to record HOW LONG it takes for the amylase to break down all the starch. To do this, use a dropping pipette to take a FRESH SAMPLE from the boiling tube EVER 30 SECONDS and put a DROP into a WELL. When the iodine solution REMAINS BROWNY-ORANGE, starch is no longer present.

7. REPEAT the whole experiment with buffer solutions of different pH VALUES to see how pH AFFECTS the time taken for the starch to be broken down.

8. Remember to CONTROL ANY VARIABLES each time (e.g. the concentration and volume of amylase solution) to make it a FAIR TEST.

9. Remember to repeat the experiment at LEAST THREE TIMES at each pH and work out the mean time taken for starch to break down.


Exam tip- make sure you don't forget to do a risk assessment before you do this experiment.

Explain what safety precautions should be taken when doing this experiment.

You should always take basic safety precautions like wearing GOGGLES and a LAB COAT.


How could you improve the accuracy of your results for this experiment?

Instead of using the bunsen burner, tripod and gauze, you could set an electric water bath to 35℃ and place the boiling tube in that.

You could use a pH meter to accurately measure the pH of your solutions.


What are the problems with this experiment?

How can you solve these problems?

-We are only taking samples every 30 SECONDS.
This means that we only have an APPROXIMATE TIME for the reaction to COMPLETE. We could address this by taking samples every ten seconds.

- We are looking for the time when the iodineDOES NOT GO BLUE-BLACK. This is not always obvious. The colour change tends to be GRADUAL. Some wells might have a small amount of blue-black mixed with orange, so it can be difficult to see when the reaction has finished.

One way to address that problem is to ask SEVERAL people to look at the spotting tile and decide when the REACTION has COMPLETED.


How do you calculate the rate of reaction?

Rate is a measure of how much something changes over time.

Rate = 1000

E.g. At pH 6, the time taken for amylase to break down all of the starch in a solution was 90 seconds.

So the rate of reaction= 1000 ÷ 90 = eleven seconds minus 1 (2.s.f.) (go to page 29 to see answer).


Practice Questions: A group of students were investigating the effect of pH on the rate of starch breakdown by the enzyme amylase. They mixed the enzyme and starch in a boiling tube, then every 10 seconds added a drop of the mixture to a well on a spotting tile containing iodine solution. They timed how long it took for all of the starch to be broken down.

a) Explain how the pH level of the enzyme and starch mixture could be controlled.

b) Explain how the students would know when all of the starch had been broken down.

c) It took 120 seconds for all the starch to be broken down. Calculate the rate of reaction.

a) By adding a buffer solution to the boiling tube containing the enzyme and starch mixture.

b) The iodine solution would remain browny-orange rather than changing to blue-black.

c) Rate = 1000 1000
------- = --------
time 120

= 8.3 s-1 (2.s.f)


What is the digestive system and its function?

The digestive system is an ORGAN SYSTEM in which SEVERAL organs work together to DIGEST (break down) food, so that nutrients can be ABSORBED into the body from the gut.


Explain the 2 ways in which food is broken down?

Food is broken down in two ways:

1) By mechanical digestion- this include our teeth grinding down food and our stomach churning up food.

2) By chemical digestion- where enzymes help to break down food.


What are the 3 main nutrients in food?

Food contains three main nutrients: CARBOHYDRATES (e.g. starch), PROTEIN and LIPIDS (fats).


What is the role of digestive enzymes?

STARCH, PROTEINS and fats are big molecules. They're too big to pass through the walls of the digestive system, so DIGESTIVE ENZYMES break these big molecules down into smaller ones like SUGARS (e.g. glucose and maltose), AMINO ACIDS, GLYCEROL and FATTY ACIDS. These smaller, SOLUBLE molecules can PASS EASILY through the walls of the digestive system, allowing them to be ABSORBED into the BLOODSTREAM.


How are the products of digestion used?

They can be used to make new carbohydrates, proteins and lipids. Some of the glucose (a sugar) that's made is used in respiration.


Name the type of enzyme that catalyses the breakdown of carbohydrates.

Carbohydrases catalyse carbohydrates. AMYLASE is an example of a carbohydrase.


What does amylase break down?

Amylase breaks down carbohydrates into SIMPLE SUGARS.

E.g. Starch --------------> Maltose (and other simple sugars)


Name the digestive enzyme produced in the salivary glands.

AMYLASE is made in the salivary glands.


Where is amylase produced?

Amylase is made in the salivary glands, the pancreas and the small intestine. It works in the mouth and the SMALL INTESTINE.


Name the type of enzyme that catalyses the breakdown of proteins.

PROTEASE enzymes are digestive enzymes that catalyse PROTEINS.


What does protease break down?

Protease enzymes are digestive enzymes that catalyse the conversion of proteins into AMINO ACIDS.


Where is protease produced?

Proteases are made in the STOMACH, the PANCREAS and the SMALL INTESTINE.


Name the type of enzyme that catalyses the breakdown of lipids.

What does this enzyme produce?

Lipase enzymes are digestive enzymes that catalyse the conversion of LIPIDS into FATTY ACIDS and GLYCEROL.


Where are lipase produced?

Lipase are made in the PANCREAS and the SMALL INTESTINE.


What is bile?

Bile is an ALKALINE.


Where is bile produced?

Bile is produced in the LIVER.


Where is bile stored?

Bile is stored in the GALL BLADDER.


Where is bile released?

Bile is released in the SMALL INTESTINE.


Describe how bile produces ideal conditions for enzymes in the small intestine to work in.

The HYDROCHLORIC ACID in the stomach makes the pH TOO ACIDIC for enzymes in the small intestine to work properly. Bile is ALKALINE- it NEUTRALISES the acid and makes conditions ALKALINE. The enzymes in the small intestine WORK BEST in these alkaline conditions.


How does bile increase the rate of lipid digestion?

it EMULSIFIES fats. In other words it breaks the fat into TINY DROPLETS. This gives a much BIGGER SURFACE AREA of fat for the enzyme lipase to work on-which makes its digestion FASTER.


Where are digestive enzymes produced?

Enzymes used in the digestive system are produced by specialised cells in GLANDS and in the GUT LINING.


What is the structure of proteins?

Proteins are LONG CHAINS of chemicals called AMINO ACIDS.


What is the role of protease enzymes?

When we digest proteins, the protease enzymes convert the protein back to the individual AMINO ACIDS, which are then ABSORBED into the BLOODSTREAM.


What occurs to the amino acids once absorbed by the body cells?

When the amino acids are absorbed by the body cells they are joined together in a DIFFERENT ORDER to make HUMAN PROTEINS.


What is starch?

Starch consists of a chain of glucose molecules.


What does a lipid molecule consist of?

A lipid molecule consists of a molecule of GLYCEROL attached to three molecules of FATTY ACIDS.


Is bile an enzyme?



What 3 places does digestion occur?

1) Mouth
2) Stomach
3) Small intestine


What is absorption?

Absorption is the movement of digested food molecules through the wall of the intestine and into the blood stream or lymph


Where is digested food absorbed?

The small intestine.


Where does the digestive process begin?

Digestion begins as food enters the mouth. This process is called ingestion.


What happens when the food enters the mouth?

Food is MECHANICALLY broken down into SMALLER pieces in the mouth by CHEWING. The teeth cut and crush food, and the pieces are mixed with SALIVA to form a ball of food called a BOLUS.


What do the salivary glands produce?

Salivary glands produce AMYLASE in the SALIVA.


What happens when after food is ingested and a bolus is formed?

The bolus the passes down the OESOPHAGUS and into the STOMACH


How is food moved through the digestive system?

Food is moved through the digestive system by a process called PERISTALSIS.


Define peristalsis.

Define alimentary canal.

-Wave-like muscular contractions in the smooth wall of the gut which move food through the alimentary canal.

-The digestive tract which runs from mouth to anus.


How are the muscular contractions in peristalsis caused?

Two sets of muscles in the gut wall are involved:

-circular muscles - which reduce the DIAMETER of the gut when they contract

-longitudinal muscles - which reduce the LENGTH of the gut when they contract


What is the result of these muscular contractions produced by circular & longitudinal muscles?

The muscles work together to produce wave-like contractions. These have a ‘squeezing action’ that pushes the bolus through the GUT.

N.B. Peristalsis continues to move food through the small intestine and the large intestine


What 2 things does the stomach produce?

It produces the PROTEASE enzyme, PEPSIN.



Why does the stomach produce HCl?

2) To give the RIGHT pH for the PROTEASE enzyme to work (pH 2- ACIDIC).


How does the stomach break down food mechanically?

It PUMMELS the food with its muscular walls.


Where does the food travel after the stomach?

After it has been in the stomach, food travels to the small intestine.


What does the small intestine produce?

Where happens to the food in the small intestine?

-Produces PROTEASE, LIPASE and AMYLASE enzymes to complete digestion.

-This is also where the digested food is ABSORBED out of the digestive system into the blood.


What pH do the enzymes in the small intestine work best in? Why is this a problem?

The enzymes in the small intestine work best in alkaline conditions - but the food is acidic after being in the stomach.


How does bile create an alkaline pH in the small intestine?

( Bile is a substance produced by the liver and stored in the gall bladder.)

Bile is secreted into the small intestine where it has two effects:

-it neutralises the acid - providing the alkaline conditions needed in the small intestine

-it emulsifies fats - providing a larger surface area over which the lipase enzymes can work


What is the role of the small intestine?

The small intestine is the region where digested food is absorbed.


How long is the small intestine?

It is between 6 and 7 metres long.


How is the small intestine adapted for its function?

This is the longest part of the small intestine and is between 2-4 metres long. The small intestine has a LARGE INTERNAL SURFACE AREA for absorption to happen QUICKLY and EFFICIENTLY.

The SI also contain villi.


What are villi?

The villi (one is called a villus) are tiny, finger-shaped structures that increase the surface area.


How do the villi aid absorption in the SI?

-Wall just one cell thick - ensures that there is only a short distance for absorption to happen by DIFFUSION and ACTIVE TRANSPORT.

-Network of blood capillaries - transports GLUCOSE and AMINO ACIDS away from the small intestine in the blood.

-Internal structure called a lacteal - transports FATTY ACIDS and GLYCEROL away from the small intestine in the lymph.


What is assimilation?

Assimilation is the movement of digested food molecules into the cells of the body where they are used. For example:

-Glucose is used in respiration to provide energy.
-Amino acids are used to build new proteins.


What is the role of the liver in assimilation?

The liver is important in assimilation. For example, it converts glucose into GLYCOGEN (a complex carbohydrate used for storage) and amino acids into PROTEINS.


What is the role of the liver in deamination?

The liver is involved in the process of deamination. This is the removal of the nitrogen-containing part of amino acids, to form urea, followed by the RELEASE OF ENERGY from the remainder of the amino acid.


What is egestion?

The process of passing out the remains of food that has not been digested, as faeces, through the anus.


What does the small intestine absorb?

What does the remaining material consist of?

-The small intestine absorbs most of the water in the contents of the gut. By the time the contents reach the end of the small intestine, most of the digested food has also been absorbed.

-The remaining material consists of:
bacteria (living and dead)
cells from the lining of the gut
indigestible substances - such as cellulose from plant cell walls


What is the colon?

What is the function of the large intestine?

The colon is the first part of the large intestine.

It is where EXCESS WATER is ABSORBED from food.


Once the colon absorbs remaining water what is left?

This leaves semi-solid waste material called faeces.


Where are faeces stored?

The faeces (made up of mainly indigestible food) are stored in the rectum, the last part of the large intestine.

Egestion happens when these faeces pass out of the body through the anus.


What is the glucose produced in digestion used for?

Some of the glucose produced is used in RESPIRATION.


What are glands made up of?

Glands are made up of glandular tissue and specialised cells that produce digestive enzymes.


What is epithelial tissue and what does it do?

All organs in the digestive system have epithelial tissue which covers the stomach inside and out.

It PROTECTS the stomach, helps keep its structure and allows substances to be exchanged through it.


How do you prepare a food sample?

1. Get a piece of food and BREAK IT UP using a PESTLE and MORTAR.

2. Transfer the ground up food to a BEAKER and add some DISTILLED WATER.

3. Give the mixture a good STIR with a glass rod to DISSOLVE some of the food. (Stir so the chemicals in the food dissolve in the water).

4. FILTER the solution using a funnel lined with filter paper to GET RID of the SOLID bits of food.


What are the two types of sugar?

There are 2 types of sugar- NON-REDUCING and REDUCING. You can test for REDUCING SUGARS .


How can you test for reducing sugars in food sample?

1) Prepare a FOOD SAMPLE and transfer 5 ㎤ to a test tube.

2) Prepare a WATER BATH so that it is set to 75℃.

3) Add some BENEDICT'S SOLUTION to the test tube (about 10 DROPS) using a pipette.

4) Place the test tube in the water bath using a test tube holder and leave it in there e for 5 minutes. Make sure the tube is POINTING AWAY from you.

5) If the food sample contains a reducing sugar, the solution in the test tube will change from the normal BLUE colour to green, yellow or brick-red- it depends how much sugar is in the food.


Exam tip- Make sure you're aware of the risks of the Benedict's test before you start. Wear eye protection and be very careful around the hot water in the water bath.

Name the reagent used to test for the presence of starch.

IODINE SOLUTION is used to test for the presence of starch.


What colour is iodine solution?

What are the risks of the experiment?

Iodine solution is a BROWNY-ORANGE colour.

The risks of iodine starch is that iodine is an irritant to the eyes. So you must wear eye protection.


How can you test for starch in a food sample?

1. Make a FOOD SAMPLE and transfer 5 ㎤ to a test tube.

2. Then add a few drops of IODINE SOLUTION and GENTLY SHAKE the tube to mix the contents. If the sample contains starch, the colour of the solution will change from BROWNY-ORANGE to BLACK or BLUE-BLACK.


if starch is present in a food sample what colour does the iodine solution go?

Black or blue-black.


Name the reagent used to test for the presence of proteins.

What are the risks of food tests for proteins?

The agent used is called BIURET SOLUTION.

The chemicals in the buret solution are dangerous, so you'll need to wear safety goggles and make sure that you wash it off straight away if you get it on your skin.


What colour is buret solution?

Biuret solution is BLUE.


What foods are used when testing for the presence of protein?

Meet and cheese are protein rich and good foods to use in this test.


How can you test for proteins in a food sample?

1) Prepare a SAMPLE of your food and transfer 2 ㎤ of your sample to a test tube.

2) Add 2 ㎤ of BIURET SOLUTION to the sample and mix the contents of the tube by GENTLY SHAKING it.

3) If the food sample contains protein, the solution will change from BLUE to PINK or PURPLE.
If no protein is present, the solution will stay blue.


Name the reagent used to test for the presence of lipids.

You can test for lipids in a food using SUDAN III STAIN SOLUTION.



What are the risks of food tests for lipids?

It is red.

Make sure you wear safety goggles. Also Sudan III stain solution is flammable, so make sure you keep it away from any lit Bunsen burners.


How can you test for lipids?

1) Prepare a SAMPLE of food you are testing (but you don't need to filter it.

2) Use a pipette to add 3 drops of SUDAN III STAIN SOLUTION to the test tube and GENTLY SHAKE the tube.

3) Sudan III stain solution STAINS lipids. If the sample contains lipids, the mixture will separate out into TWO LAYERS. The top layer will be BRIGHT RED. If no lipids are present, no separate red layer will form at the top of the liquid.