topic 2 Flashcards
1
Q
What is the job of muscular tissue, glandular tissue and epithelial tissue?
A
Muscular-contracts to move whatever it’s attached to, and moves stomach wall to churn food. Glandular-makes and secrets chemicals e.g. enzymes and hormones, and makes digestive jucies to digest food. Epithelial-covers some parts of body e.g. inside of gut, and covers outside and inside of stomach.
2
Q
What is a tissue?
A
group of similar cells that work together to carry out a particular function.
3
Q
What is an organ?
A
Group of different tissues that work toghther to perform a certain function.
4
Q
What is an organ system?
A
group of organs working together to perform a particular function.
5
Q
What is an enzyme?
A
A biological catalyst. Enzymes reduce the need for high temperatures and we only have enzymes up to speed the useful chemical reactions in the body. A catalys is a substance which increases the speed of a reaction without being changed or used up in the reaction. Enzymes are all large proteins and all protiens are made up of chains of amino acids. These chains are folded into unique shapes, which enzymes need to do their jobs.
6
Q
What is an active site and substrate?
A
Every enzyme has an active site with a unique shape that fits onto the substrate involved in a reaction. Enzymes useually only catalyse 1 specific reaction. Becuase for enzyme to work, substrate has to fit into its active site. If substrate doesn’t match enzyme’s active site, then the reaction won’t be catalysed.
7
Q
What is the ‘lock and key model’?
A
See revison guide.
8
Q
How can changing the temperature have an effect on the enzyme?
A
Higher temperature increases rate at first. But if gets too hot, some of bonds holding enzyme together break. Changes the shape of enzyme’s active site, so substrate won’t fit any more. Enzyme is said to be denatured. All enzyms have an optimum temperature that they work best at.
9
Q
How can changing the pH have an effect on the enzyme?
A
If too high or low, pH interferes with bonds holding enzyme together. This changes shape of active site and denatures the enzyme. All enzymes have a optimun pH that they work best at. It’d often neutral pH 7. E.g. pepsin is an enzyme used to break down proteins in stomach. It works best at pH2, which means it is more suited to acidic conditions there.
10
Q
What is amylase used for?
A
Breakdown starch to maltose. Easy to detect starch using iodine solution-if starch present iodine solution will change from browny-orange ot blue-black.
11
Q
What are the first steps to test for starch?
A
Put a drop of iodine solution into every well of spotting tile. Place bundsen burner on a heat-proof mat, a tripod and gauze over bundsen burner. Put beaker of water ontop of tripod and heat water until its 35 Celcius (use thermometer to measure temperature). Try to keep temperature of water constant throughout experiment.
12
Q
What do you do after you have measured the temperature of the water?
A
Use a syring to add 1cm3 of amylase solution and 1cm3 of a buffer solution with a pH of 5 to a boiling tube. Using test tube holdrs, put tube into beaker of water and wait for 5 minuites. Next use a differenet syringe to add 5cm3 of a starch solution to boiling tube. Immediatly mix contents of boiling tube abd start stop clock.
13
Q
What do you do with continuous sampling?
A
Record how long takes foramylase to break down all of starch. To do this, use a dropping pipette to take a fresh sample from boiling tube every 30 seconds and put a drop into a well. When iodine solution remains browny-orange, starch is no longer present.
14
Q
Why do we repeat the experiment with buffer solutions of different pH values?
A
To see how pH affects time taken for starch to be broken down. Remeber to control variables each time. (e.g. concentration and volume of amylase solution) to make it a fair test.
15
Q
Does rate of reaction change over time?
A
Yes
16
Q
What is the formula for rate of reaction?
A
rate=1000/time. Units aer in s-1 since rate is given per unit.
17
Q
What does an experiment and calculations do?
A
Experiment: meaures how much something changes over time.
Calculation: can calculate rate of reaction by dividing amount that it has changed by time taken.
18
Q
Why does digestion need to break dow food to smaller molecules?
A
so they can pass through walls of digestibe system easily, alowing them to be aborbed into blood stream.
19
Q
What is the examle of carbohydrases convert carboyhdrates into simple sugars?
A
Amylase is example of carbohydrase-breaks down starch. see revision guide. Amylse found in slaivaryglands, pancreas and small intestine.
20
Q
What is the example of proteases convert proteins into amino acids?
A
see revision guide
proteins are found in stomach (called papsin there)
pancreas
small intestine.
21
Q
What is the example of lipase convert lipids into glycerol and fatty acids?
A
See revision guide. Lipases found in pancreas and small intestine.
22
Q
What are the products of digestin used as?
A
new carbohydrates, proteins and lipids. Some of glucose (carbohydrate) that is used in respiration.
23
Q
What is the example of bile to emulsifie fat?
A
Produced in liver, stored in gall bladder before released into small intenstine. Hydrochloric acid in stomach makes ph too acidic for enzymes in small intestine to work properly. Bile is alkalint-neutralises acid and makes conditions alkaline. Enzyme in small intestine works best in these alkaline conditions. It emulsifies fats. It breaks down fat into tiny droplets. Gives much bigger surface area of fat for enzyme lipase to work on-makes digestion faster.
24
Q
What happens in the salivary glands?
A
produce amylase enzyme in saliva.
25
What happens in the liver?
Bile is produces.
26
What happens in the stomach?
pummels food with its muscular walls, produces protease enzyme, pepsin, produces hydrochloric acid for 2 reasons, to kill bacteria and to give the right pH for the protease enzyme to work. pH2-acidic
27
What happens in the gall bladder?
Bile is stored before it's releaed into small intestine.
28
What happens in pancreas?
Produces protease, amylase and lipase enzymes. Releases these into small intestine.
29
What happens in the large intestine?
Excess water is absorbed.
30
What happens in small intestine?
Produces protease, amylase and lipase enzymes to complete digestion. Also where digested food is absorbed out of digestive system into blood.
31
What do you do to prepare a food test?
get a piece of food and break it up using pestle and mortar, transfer ground up food to beaker, add some distilled water, give mixture a good stir with a glass tod to dissolve some of foodm filter solution using funnel lined with filter papaer to get rid of solid bits of food.
32
What do you do for the Benedict's test to test for reduced sugars?
2 types of sugars, reducing and non-reducing. First prepare food sample and transfer 5cm3 to test tube, prepare water bath so that it's set to 75 Celcius, add some Benedict's soution to test tube (about 10 drops) using pipette. Place test tube in water bath using test tube holder and leave it ther for 5 minuites. Make sure tube is pointing away from you, If food contains reducing sugar, solution in test tube will change from normal blue to green yellow or brick-red-depends on how much sugar is in food.
33
What is involved in iodine soluition to test for starch?
Make food sample and transfer 5cm3 of sample to test tube, add a few drops of iodine solution and gently shake the tube to mix contents. If sample contains starch, colour of solution will change from browny-orange to blakck or blue-black.
34
What is involved for the biuret test to test for proteins?
Prepare sample of food transfer 2cm3 of sample to test tube, add 2cm3 of biuret solution to sample and mix contents of tube by gently shaking it. If food sample contains protein, solution will change from blue to pink or purple. If no protein is present, solution stay blue.
35
What is involved to use Sudan III to test for lipids?
prepare sample of food you're testing (but don't need to filter it) .Transfer 5cm3 into test tube, use pipette to add 3 drops of Sudan III stain solution ot test tube and gently shake tube. Sudan III stain solution stains lipids. If smaple contains lipids, mixture will seperate out into 2 layers. Top layer will be bright red. If no lipids present, no seperate red layer will form at top layer of liquid.
36
What is the stucture of the lungs?
Thorax is top part of body, is seperated from lower part of body by diaphragm. Lungs are bink pink sponges and are protected by the ribcage. They're surrounded by pleural membranes.
37
What happensafter you breath in air?
goes through trachea. Splits into 2 tubes called bronchi (each one is bronchus), 1 going to each lung. Bronchi split into progressively smaller tubes called bronchioles. Bronchioles finally end at small bags called alveoli where gas exchange takes place.
38
how is gas exchanged
blood passing next ot alveoli just returned to lungs from rest of body, so contains lots of co2 and very little oxygen. Oxygen diffuses out of alveolus (high concentration) into blood (low concentration) into alveolus (low concentration) to be breathed out.
39
What happens in gas exchange?
When blood reaches body cells oxygen is released from red blood cells (high concentration) and diffuses into body cells (low concentration). At same time co2 diffuses out of body cells (high concentration) into blood (low concentration). Then carried back to lungs.
40
How do you calculate breathing rate in breaths per minuite?
breaths/minuites.
41
What is the circulatory sytem made of?
Blood vessels, heart, blood.
42
What are the stages of the circulatory system?
First one: Right ventricle pumpsc deoxygenated blood to lungs to take in oxygen. Blood returns to heart.
Second one:Left ventricle pumps oxygenated blood around all other organs of body. Blood gives up its oxygen at body cells and deoxygenated blood returns to heart to be pumped out to lungs again.
43
What tissue are the walls of heart mainly made of?
Muscle tissue
44
What are valves used for?
To prevent the backflow of blood.
45
What happesn when blood flows into the 2 atria form the vena carva and pulmary vein?
The atria contract, pushing blood into ventricles, ventricles contract, forcing blood into pulmary artery and aorta and out of heart. Blood then flows to organs through arteries, and returns through veins. Atria fill again and the cycle begins again.
46
Doest the heart have its own supply of oxygenated blood?
Yes.
47
What are coronary arteries?
branch off aorta and surround heart, making sure it gets all oxygenated blood it needs.
48
what is a pacemaker?
Your resting heart is controlled by a group of cells in right atrium wall that act as a pacemaker. These cells produce a small electric impulse which spreads to surrounding muscle cells, causing them to contract.
49
What is an artificial pacemaker?
An artificial pacemaker is often used to control heartbeat if the natural pacemaker cells don't work properly (e.g. if the patient has an irregular heartbeat). It's a little device that's implanted under the skin and has a wire going to the heart. It produces and electric current to keep the heart beating regularly.
50
what are arteries, capillaries and veins?
Arteries: carry blood away from heart.
Capillaries: involved in exchange of materials at tissue
Veins: carry blood to heart
51
What are the properties of arteries?
Heart pumps blood out at high pressure so artery walls are thick compared to size of hole in middle (lumen). They contain thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back.
52
What are properties of capillaries?
Arteries branch into capillaries, capillaries are tiny-too small to see, carry blood close to every cell in body to exchange substances. Have permeable walls, so substances diffuse in and out. Supply food and oxygen, and take away waste e.g. co2. Walls usually 1 cell thick. Increases rate of diffusion by decreasing distance over which it occurs.
53
What are the properties of veins?
Capillaries eventually join up to form veins. Blood is at lower pressure in veins so walls don't need to be as thick as artery walls. Have bigger lumen than arteries to help blood flow despite lower pressure. Also have values to help keep blood flowing in right direction.
54
How do you calculate the rate of flow of oxygen?
rate of blood flow-volume of blood/number of minutes.
55
How are red blood cells adapted for their job?
Job is to carry oxygen from lungs to all cells in body. Shape is biconcave disc gives large surface area for absorbing oxygen. Don't have nucleus-allows more room to carry oxygen. Contain red pigment called haemoglobin. In lungs, haemoglobin binds to oxygen to become oxyhaemoglobin. In body tissues, reverse happens-oxyhaemoglobin splits up into haemoglobin and oxygen to release oxygen to cells.
56
How are white blood cells adapted for their job?
Some can change shape to gobble up unwelcome microorganisms, in process called phagocytosis. Others produce antibodies to fight microorganisms as well as antitoxins to neutralise any toxins produced by microorganisms. Unlike red blood cells, have nucleus.
57
How are platelets adapted for their job?
small fragments of cells. Have no nucleus. Help blood to clot at wound-to stop all blood pouring out and to stop microorganisms getting in. Lack of platelets can cause excessive bleeding and bruising.
58
How are plasma adapted for their job?
Is pale straw-coloured liquid which carries just about everything. Red and white blood cells and platelets. Nutrients like glucose and amino acids. Are soluble products of digestion which are absorbed by gut and taken to cells of body. co2 from organs to lungs, urea from liver to kidneys, hormones, proteins, antibodies and antitoxins produced by white blood cells.
59
What is coronary heart disease?
When coronary arteries that supply blood to muscle of hart get blocked by layers of fatty material building up. Causes arteries to become narrow, so blood flow is restricted and lack of oxygen to heart muscle-can result in heart attack.
60
What are stents?
tubes that are inside arteries. Keep them open, making sure blood can pass through heart muscles. Keeps person's heart beating. Are way of lowering risk of heart attack in people with coronary heart disease. Are effective for long time and recovery tome from surgery is relatively quick.
61
What are negatives of stents?
Risk of complications during operation (e.g. heart attack) and risk of infection from surgery. Also risk of patients developing blood clot near stent, called thrombosis.
62
What is cholesterol?
Essential lipid that body produces and needs to function properly. However, too much of certain type of cholesterol (known as LDL cholesterol) can cause health problems.
63
How is having too much cholesterol in bloodstream bad for you?
Can cause fatty deposits to form inside arteries, can lead to coronary heart disease. Statins are drugs that can reduce amount of 'bad' cholesterol present in bloodstream. Slows down rate of fatty deposits forming.
64
What are the advantages of statins?
By reducing amount of 'bad' cholesterol in blood, statins can reduce risk of strokes, coronary heart disease and heart attacks. As well as reducing amount of 'bad' cholesterol, statins increase amount of beneficial type of cholesterol (known as HDL cholesterol) in bloodstream. This type can remove 'bad' cholesterol from blood. Some studies suggest that statins may also help prevent some other diseases.
65
What are disadvantages to statins?
Statins are long-term drug that must be taken regularly. Is risk that someone could forget to take them. Statins can sometimes cause negative side affects, e.g. headaches. Some of these side affects can be serious, e.g. kidney failure, liver damage and memory loss. Effect of statins isn't instant. Takes time for effect to kick in.
66
What happens if someone has heart failure?
Doctors may perform heart transplant, using donor organs from people who have died recently. However, if donor organs aren't available or they're not best opinion, doctors may fit an artificial heart.
67
What are artificial hearts?
Mechanical devices that pump blood for a person whose heat has failed. Usually only used as temporary fix, to keep person alive until donor heart can be found or to help person recover by allowing heart to rest and heal. In some cases though they're used as permanent fix, which reduces need for donor heart.
68
What are the advantages for artificial heart?
less likely to be rejected by body's immune system than donor heart. Because made from metals or plastics, so body doesn't recognise them as 'foreign' and attack in same way as it does with living tissue.
69
What can happen when putting in an artificial heart?
Can lead to bleeding and infection (as with transplant surgery). Also, artificial hearts don't work as well as healthy natural ones-parts of heart could wear out or electrical motor could fail. Blood doesn't flow through artificial hearts as smoothly, which can cause blood clots and lead to strokes. Patient has to take drugs to thin blood and make sure doesn't happen, can cause problems with bleeding if they're hurt in an accident.
70
what can damage valves in heart?
heart attacks, infection or old age.
71
What may damage of heart valves cause?
Valve tissue to stiffen, so won't open properly. Or valve may become leaky, allowing blood to flow in both directions rather than just forward. Means that blood doesn't circulate as effectively as normal.
72
What does valve damage need to be 'cured' by?
replacing valve. Valve can be taken from humans or other mammals-biological valves. Or they can be man-made-mechanical valves. Replacing valve is much less drastic than whole heart transplant. But fitting artificial valves is still major surgery and can still be problems with blood clots.
73
When is artificial blood used?
If lots of blood lost in emergency.
74
What is artificial blood?
Blood substance e.g. salt solution ("saline") is used to replace lost volume of blood. Safe (if no air bubbles get into blood) and can keep person alive even if lose 2/3 of red blood cells. May give patient enough time to produce new blood cells. if not patient will need blood transfusion.
75
What should happen ideally with artificial blood?
Would replace function of lost red blood cells, so no need for blood transfusion. Scientists currently working on products that can do this.
76
What is health?
state of physical and mental wellbeing. Diseases often responsible for causing ill health
77
What are communicable diseases?
Can be spread from person to person or between animals and people. They can be caused by things like bacteria, viruses, parasites and fungi. They're sometimes describes as contagious or infectious diseases. Measles and malaria are examples of communicable diseases.
78
What are non-communicable diseases?
Cannot spread between people or between animals and people. Generally last for long time and get worse slowly. Asthma, cancer and coronary heart disease are examples of non-communicable diseases.
79
What does is mean having a problem with their immune system?
Have increased chance of suffering from communicable diseases such as influenza (flu), because body is less likely to be able to defend itself against pathogens that causes disease.
80
What can some types of cancer be triggered by?
infection by certain viruses. E.g. infection with some types of hepatitis virus can cause long-term infections in liver, where virus lives in cells. Can lead to an increased chance of developing liver cancer. Another example is infection with HPV (human papilloma virus) which can cause cervical cancer in women.
81
What are immune system reactions?
In body caused by infection by pathogen can sometimes trigger allergic reaction such as skin reactions such as skin rashes or worsen symptoms of asthma for asthma sufferers.
82
What is mental health issues?
Such as depression can be triggered when someone is suffering from severe physical health problems, particularly if have an impact on person's ability to carry out everyday activities or if they affect person't life expectancy.
83
What other factors can affect your health?
Whether or not have good, balanced diet that provides body with everything it needs, and in right amounts. A poor diet can affect physical and mental health. Stress under-being constantly under lots of stress can lead to health issues.
84
How can your life situation affect your health?
E.g. whether you have easy access to medicines to treat illness, or whether have access to things that can prevent from getting sick in first place e.g. being able to buy healthy food or access condoms to prevent transmission of some sexually transmitted diseases.
85
What are risk factors?
Things linked to an increase in likelihood that a person will develop a certain disease during their lifetime. They don't guarantee that someone will get the disease. Often aspects of person's lifestyle. Can also be presence of certain substances in environment or substances in body. Many non-communicable diseases caused by several different risk factors interacting with each other rather than 1 factor alone.
86
How can lifestyle factors be different impacts locally, nationally and globally?
In developed countries non-communicable diseases are more common as people generally have higher income and can buy high-fat food. Nationally people from deprived areas are more likely to smoke, have poor diet and not exercise. Means incidence of cardiovascular disease, obesity and type 2 diabetes is higher in those areas. Individual choices affect local incidence of disease.
87
How can smoking affect your health?
been proven to directly cause cardiovascular disease, lung disease and lung cancer. Damages walls of arteries and cells in lining of lungs. Smoking when pregnant can cause lots of health problems for unborn baby. Drinking alcohol has similar affects.
88
How does obesity affect your health?
Thought that obesity can directly cause type 2 diabetes by making body less sensitive or resistant to insulin, meaning it struggles to control concentration of glucose in blood.
89
How can alcohol affect your health?
Been shown to cause liver disease. Too much alcohol can affect brain function too. Can damage nerve cells in brain causing brain to lose volume.
90
What can potentially cause cancer?
By exposure to certain substances or radiation. Causes of cancer are known as carcinogens. Ionising radiation (e.g. from x-rays) is example of carcinogen.
91
How are risk factors useful for science?
Identified by scientists looking for correlations in data, and correlation doesn't always equal cause. Some risk factors aren't capable of directly causing disease. E.g. lack of exercise and high fat diet are heavily linked to increase chance of cardiovascular disease, but can't cause disease directly. It's the resulting high blood pressure and high 'bad' cholesterol levels that can actually cause it.
92
How can non-communicable diseases affect humans?
Tens of millions of people around world die from non-communicable diseases per year. People with diseases may have lower quality of life or shortened lifespan. Not only affects sufferers themselves.
93
How can non-communicable diseases affect finances?
Cost NHS researching and treating these diseases is huge-same for other health services and organisations around world. Families may have to move or adapt home to help family member with disease, can be costly. If family member with disease has to give up work or dies, reduced family income. Reduction in number of people able to work can also affect country's economy.
94
What is cancer?
Uncontrolled growth and division is result of changes that occur to cell and results in formation of tumour (mass of cells). Not all tumours are cancerous. Can be benign or malignant.
95
what is a benign tumour?
Where tumour grows until there's no more room. Tumour stays in 1 place (usually within a membrane) rather than invading other tissues in body. This type isn't normally dangerous, and tumour isn't cancerous.
96
What is a malignant tumour?
Where tumour grows and spreads to neighbouring healthy tissues. Cells can break off and spread to other parts of body by travelling to bloodstream. Malignant cells then invade tissues elsewhere in body and form secondary tumours. Malignant tumours are dangerous and can be fatal-cancers.
97
How is smoking a risk factor for cancer?
Well known fact 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.
98
how is obesity a risk factor for cancer?
Obesity has been linked to many different cancers, including bowel, liver and kidney cancer. Is second biggest preventable cause of caner after smoking
99
How is UV exposure a risk factor for cancer?
People who often exposed to UV radiation from sun have increased chance of developing skin cancer. People who live in sunny climates an people who spend a lot of time outside are at higher risk of disease. People who frequently use sun beds are also putting themselves at higher risk of developing skin cancer.
100
How are viral infections a risk factor for cancer?
infection with some viruses has been shown to increase chances of developing certain types of cancer. E.g. infection with hepatitis B and hepatitis C with these viruses sometimes depends on lifestyle-e.g. can spread between people through unprotected sex or sharing needles.
101
How can risk factors be associated with genetics?
Sometimes can inherit faulty genes that make more susceptible to cancer. E.g. mutations (changes) in BRCA genes have been linked to an increased likelihood of developing breast and ovarian cancer.
102
What is the epidermal tissue?
Covers whole plant.
103
What is the palisade mesophyll tissue?
Part of leaf where photosynthesis happens.
104
What is the spongy mesophyll tissue?
Contains big air spaces to allow gases to diffuse in and out of cells.
105
What are xylem and phloem?
Transport things like water, mineral ions and food around plant (through roots, stems and leaves).
106
What are meristem tissues?
Found at growing rips of shoots and roots and able to differentiate into lots of different tissues of plant cell, allowing plant to grow.
107
What types of tissue do leaves contain?
Epidermal, mesophyll, xylem and phloem tissue.
108
Where are epidermal tissue found?
Covered with waxy cuticle, which helps reduce water loss by evaporation.
109
What is the upper epidermis?
Is transparent so that light can pass through it to the palisade layer.
110
What is the palisade layer?
Has lots of chloroplasts (little structures where photosynthesis takes place). Means that they're near top of leaf where can get most light.
111
What are xylem and phloem?
Form network of vascular bundles, which deliver water and other nutrients to entire leaf and take away glucose produced by photosynthesis. Can also support structure.
112
How are the tissues of leaves adapted for efficient gas exchange?
E.g. lower epidermis is full of little holes called stomata, which let co2 diffuse directly into leaf. Opening and closing of stomata is controlled by guard cells in response to environmental conditions. Air spaces in spongy mesophyll tissue increase rate of diffusion of gases.
113
What is the structure of phloem tubes to transport food?
Made of columns of elongated living cells with small pores in end walls to allow cell sap to flow through.
114
What is the job of phloem cells?
Transport food substances (mainly dissolved sugars) made in leaves to rest of plant for immediate use (e.g. in growing regions) or for storage. The transport goes in both directions. This process is called translocation.
115
What is the structure of xylem tubes to take up water?
Made of dead cells joined end to end with no walls between then and a hole down the middle. Strengthened with a material called lignin.
116
What is the job of xylem tubes?
They carry water and mineral ions from roots to stem and leaves. Movement of water from roots, through xylem and out of leaves is called transpiration stream.
117
What is transpiration and what is it caused by?
is loss of water from plant, caused by evaporation and diffusion of water from plant's surface. Most transpiration happens at leaves. Evaporation creates slight shortage of water in leaf, and so more water is drawn up from rest of plant through xylem vessels to replace it.
118
What does more water being drawn up from the roots mean?
Is a constant transpiration stream of water through plant.
119
Is transpiration just a side-affect of way leaves are adapted fro photosynthesis?
Yes.
120
Why do laves have a stomata?
gases can be exchanged easily.
121
What happens if there is more water inside the plant than in the air outside?
Water escapes from the leaves through the stomata by diffusion.
122
What happens in the rectum?
Where faeces (made up mainly of indigestible food) are stored before they go through the anus.
123
How does light intensity affect the rate of transpiration?
brighter light, greater transpiration rate. Stomata begin to close as it gets darker. photosynthesis can't happen in dark, so don't need to be open to let co2 in. When stomata closed, very little water can escape.
124
How does temperature affect transpiration rate?
warmer it is, faster transpiration happens. When it's warm water particles have more energy to evaporate and diffuse out of stomata.
125
How does air flow affect transpiration rate?
better air flow around leaf (e.g. stronger winds) grater transpiration rate. If air flow around leaf is poor, water vapour just surrounds leaf and doesn't move away. Means is high concentration of water particles outside leaf as well as inside it, so diffusion doesn't happen as quickly. If good air flow, water vapour is swept away, maintaining a low concentration of water in air outside leaf. Diffusion then happens quickly from an area of higher concentration to area of lower concentration.
126
How doe humidity affect the rate of transpiration?
drier air around leas, faster transpiration happens. Is like what happens with air flow. If air is humid a lot of water in it already, so not much of difference between inside and outside of leaf. Diffusion happens fastest if there's really high concentration in 1 place and really low concentration in other.
127
How can you estimate the rate of transpiration?
By measuring uptake of water by plant. Because can assume water uptake by plant is directly related to water loss by leaves (transpiration). Set up apparatus, then record starting position of air bubble. Start stopwatch and record distance moved by bubble per unit time, e.g. per hour. Keep conditions constant throughout experiment e.g. if temperature and air humidity.
128
How are guard cells adapted to open and close the stomata?
When plant has lots of water, guard cells fill with it and go plump and turgid. Makes stomata open so gases can be exchanged for photosynthesis. When plant is short of water, guard cell lose water and become flaccid, making stomata close. Helps stop too much water vapour escaping. Thin outer walls and thickened inner walls make opening and closing work. Also sensitive to light and close at night to save water without losing out on photosynthesis. Can find more stomata on underside of leaves than on top. Lower surface is shaded and cooler-so less water is lost through stomata than if they were on upper surface.
