Topic 2- Organisation Flashcards
(301 cards)
1
Q
Define cells.
A
Cells are the basic building blocks that make up all living organisms.
2
Q
What does a specialised cell do?
A
It carries out a particular function.
3
Q
Define differentiation.
A
It is the process by which cells become specialised for a particular job.
4
Q
When does differentiation occur?
A
It occurs during the development of a multicellular organism.
5
Q
What does specialised cells form?
A
It form tissues, which form organs, which form organs systems.
6
Q
What do large multicellular organisms have?
A
They have different systems inside them for exchanging and transporting materials.
7
Q
Define a tissue.
A
It is a group of similar cells that work together to carry out a particular function. It includes more than one type of cell.
8
Q
Give 3 examples of tissues in mammals.
A
- Muscular tissue
- Glandular tissue
- Epithelial tissue
9
Q
Give the function of a muscular tissue.
A
It contracts (shortens) to move whatever it’s attached to.
10
Q
Give the function of a glandular tissue.
A
It makes and secretes chemicals like enzymes and hormones.
11
Q
Give the function of an epithelial tissue.
A
It covers some parts of the body, e.g. the inside of the gut.
12
Q
Define an organ.
A
It is a group of different tissues that work together to perform a certain function.
13
Q
Give 3 tissues which the stomach is made up of.
A
- Muscular tissue
- Glandular tissue
- Epithelial tissue
14
Q
Give the function of muscular tissue within the stomach.
A
It moves the stomach wall to churn up the food.
15
Q
Give the function of glandular tissue within the stomach.
A
It makes digestive juices to digest food.
16
Q
Give the function of epithelial tissue within the stomach.
A
It covers the outside and inside of the stomach.
17
Q
Define an organ system.
A
It is a group of organs working together to perform a particular function.
18
Q
Give examples of 5 organs which makes up the digestive system.
A
- Glands (e.g. the pancreas and salivary glands)
- Stomach
- Liver
- Small intestine
- Large intestine
19
Q
Give the function of glands in the digestive system.
A
It produces digestive juices.
20
Q
Give the function of the stomach in the digestive system.
A
The stomach and small intestine, digest food.
21
Q
Give the function of the liver in the digestive system.
A
Produces bile
22
Q
Give the function of the small intestine in the digestive system.
A
Absorbs soluble food molecules
23
Q
Give the function of the large intestine in the digestive system.
A
Absorbs water from undigested food, leaving faeces.
24
Q
What are enzymes?
A
They act as biological catalyst.
25
Why do we have enzymes?
To speed up the useful chemical reactions in the body.
26
Define a catalyst.
It is a substance which increases the speed of a reaction, without being changed or used up in the reaction.
27
What are proteins made up of?
Chains of amino acids
28
What do chemical reactions usually involve?
It involves things either being split apart or joined together.
29
What does every enzyme must have to function properly?
An active site with a unique shape that fits onto the substance involved in a reaction.
30
Why do enzymes only catalyse one specific reaction?
The substrate has to fit into its active sites.
31
What happens if the substrate doesn't match the enzyme's active site?
The reaction won't be catalysed.
32
What is the substrate?
It is the substance that an enzyme acts on.
33
Name the diagram which gives the simplified version of how enzymes work.
'lock and key' model of enzyme action
34
What does the active site do when the substrate binds to it?
The active site changes shape a little as the substrate binds to it to get a tighter fit.
35
How is the 'induced fit' model of enzyme action shown?
When a substrate binds to an enzyme active site.
36
How can you change the rate of an enzyme- catalysed reaction?
By changing the temperature
37
What happens to the enzymes when the temperature is too hot? (1)
Some of the bonds holding the enzymes together break.
38
What happens to the enzymes when the temperature is too hot? (2)
This changes the shape of the enzyme's active site, so the substrate won't fit any more. The enzyme is said to be denatured.
39
What is essential for all enzymes to have in order to work efficiently?
An optimum temperature that they work best at.
40
Give another factor which affects enzymes.
pH
41
What happens to the enzymes if the pH is too high or too low?
The pH interferes with the bonds holding the enzyme together.
42
What consequence does it have on the enzyme if the pH is too high or too low?
This changes the shape of the active site and denatures the enzyme.
43
What do all enzymes must have in order to work efficiently? (2)
An optimum pH that they work best at.
44
What is the optimum pH for most enzymes?
pH 7
45
What is pepsin?
It is an enzyme used to break down proteins in the stomach (protease).
46
What does the pH of pepsin mean?
It means it's well-suited to the acidic conditions there.
47
What is the right pH for pepsin?
pH 2
48
What breaks down big molecules?
Digestive enzymes
49
Give 3 examples of big molecules broken down by digestive enzymes.
1. Starch
2. Lipids
3. Proteins
50
What is the problem with big molecules?
Too big to pass through the walls of the digestive system.
51
Give 4 examples of smaller molecules.
1. Sugars (e.g. glucose and maltose)
2. Amino acids
3. Glycerol
4. Fatty acids
52
Why are smaller, soluble molecules able to be absorbed into the bloodstream?
They can pass easily though the walls of the digestive system.
53
Give 3 locations of where amylase enzymes are used.
1. Salivary glands
2. Pancreas
3. Small intestine
54
Give the function of amylase.
Breaks down starch
55
What is amylase an example of?
Carbohydrase
56
What is starch?
A carbohydrate
57
What is starch broken down into by amylase?
Maltose and other sugars, e.g. dextrins
58
Give 3 locations for protease enzymes.
1. Stomach (it's called pepsin there)
2. Pancreas
3. Small intestine
59
Give the function of protease.
Breaks down proteins
60
What are proteins broken down into by protease?
Amino acids
61
Give 2 locations for lipase enzymes.
1. Pancreas
| 2. Small intestine
62
Give the function of lipase.
Breaks down lipids
63
What are lipids broken down into by lipase enzymes?
Glycerol and fatty acids
64
What is some of the glucose (a carbohydrate) that's made used for?
Respiration
65
What can the products of the broken down molecules be used for?
To make new carbohydrates, proteins and lipids.
66
Where is bile produced?
Liver
67
Where is bile stored?
In the gall bladder
68
Where is the bile released after being stored in the gall bladder?
Into the small intestine
69
What is the problem with hydrochloric acid for enzymes in the small intestine?
It makes the pH too acidic for enzymes in the small intestines to work properly.
70
What is bile?
It is alkaline- it neutralises the acid and makes conditions alkaline.
71
What conditions do enzymes work best at in the small intestine?
Alkaline conditions
72
What does bile do?
It emulsifies fat.
73
What does it mean to emulsify fat?
Break the fats into tiny droplets.
74
Why is it really useful to emulsify fat?
It gives a much bigger SA of fat for the enzymes lipase to work one- which makes digestion faster.
75
What are enzymes in the digestive system produced by?
Specialised cells in glands and in the gut lining.
76
Give the function of salivary glands.
These produce amylase enzyme in the saliva.
77
What does the liver produce?
Bile
78
What does bile do? (2)
Neutralises stomach acid and emulsifies fats.
79
Give the function of gall bladder.
To store bile before it's released into the small intestine.
80
Give the function of large intestine.
It is where excess water is absorbed from the food.
81
What are faeces made up of?
Made up mainly of indigestible food.
82
Give the function of rectum.
It is where the faeces are stored before they go through the anus.
83
What does the stomach produce?
1. Protease enzyme (pepsin)
| 2. Hydrochloric acid
84
Give the function of the stomach.
Pummels the food with its muscular walls.
85
Give 2 reasons why hydrochloric acid is produced in the stomach.
1. To kill bacteria
| 2. To give the right pH for the protease enzyme to work (pH 2- acidic)
86
What enzymes does the pancreas release?
1. Protease enzymes
2. Amylase enzymes
3. Lipase enzymes
87
What does the pancreas do with the enzymes?
Releases them into the small intestine.
88
What enzymes does the small intestine produce?
1. Protease enzymes
2. Amylase enzymes
3. Lipase enzymes
89
Why does the small intestine release enzymes?
To complete digestion.
90
What is the role of the small intestine?
It is where the digested food is absorbed out of the digestive system into the blood.
91
Give another name for gullet.
Oesophagus
92
Where is the thorax?
Top part of your body.
93
What is the thorax separated by?
From the lower part of the body by the diaphragm.
94
Describe what the lungs look like.
They are like big pink sponges.
95
What are the lungs protected by?
Ribcage
96
What are the lungs surrounded by?
Pleural membranes
97
Where does the air you breathe in go through?
The trachea
98
What does the trachea split into?
This splits into two tubes called bronchi (each one is a bronchus), one going to each lung.
99
What does the bronchi split into?
It split into progressively smaller tubes called bronchioles.
100
Where does the bronchioles end up at?
Small bags called alveoli.
101
Where does gas exchange take place in the lungs?
In alveoli
102
What does the lung contain?
Millions and millions of little air sacs called alveoli.
103
What are alveoli surrounded by?
A network of blood capillaries.
104
What is the circulatory system made up of?
1. Heart
2. Blood vessels
3. Blood
105
What do humans have? (circulatory system)
A double circulatory system- two circuits joined together.
106
What is deoxygenated blood?
Blood without oxygen
107
Give the function of the right ventricle.
Pumps deoxygenated blood to the lungs to take in oxygen. The blood then returns to the heart.
108
Give the function of a left ventricle.
It pumps oxygenated blood around all the other organs of the body.
109
What does the blood do when it gets at the body cells?
It gives up its oxygen and the deoxygenated blood returns to the heart to be pumped out to the lungs again.
110
What is the heart?
A pumping organs that keeps the blood flowing around the body.
111
What are the walls of the heart mostly made of?
Muscle tissue
112
What does the heart have?
Valves
113
Give the function of a valve?
To make sure that blood flows in the right direction- they prevent it flowing backwards.
114
Give 4 chambers the heart has.
1. Right atrium
2. Right ventricle
3. Left atrium
4. Left ventricle
115
What does the heart also need to function?
Its own supply of oxygenated blood.
116
How does the heart get all the oxygenated blood it needs?
By arteries called coronary arteries.
117
How is the resting heart rate controlled?
By a group of cells in the right atrium that act as a pacemaker.
118
What do pacemaker cells produce?
A small electrical impulse which spreads to the surrounding muscle cells, causing them to contract.
119
Why do some people use artificial pacemakers?
To control heartbeat if the natural pacemaker cells don't work properly.
120
In which circumstances do people need artificial pacemakers?
If the patient has an irregular heartbeat.
121
Describe an artificial pacemaker.
It's a little device that's implanted under the skin and has a wire going to the heart.
122
What does an artificial pacemaker do?
It produces an electrical current to keep the heart beating regularly.
123
Name 3 types of blood vessels.
1. Arteries
2. Capillaries
3. Veins
124
Give the function of arteries.
These carry the blood away from the heart.
125
Give the function of capillaries.
These are involved in the exchange of materials at the tissues.
126
Give the function of veins.
These carry blood to the heart.
127
Describe the pressure of how the heart pumps the blood out?
At high pressure
128
Describe the artery walls.
1. Strong
| 2. Elastic
129
What is the lumen?
The hole in the middle of a wall.
130
What can the thickness of the walls be compared to for the artery walls?
The walls are thick compared to the size of the hole down the middle.
131
What do the artery walls contain?
1. Thick layers of muscles
| 2. Elastic fibres
132
Why do arteries have thick layers of muscles?
To make them strong.
133
Why do the arteries have elastic fibres?
To allow them to stretch and spring back.
134
Where do the arteries branch into?
Capillaries
135
Describe the size of the capillaries.
They are really tiny- too small to see
136
What do the capillaries do? (1)
Carry blood really close to every cell in the body to exchange substances with them.
137
What do capillaries have?
Permeable walls
138
What do capillaries have?
Permeable walls
139
Why do capillaries have permeable walls?
So substances can diffuse in and out.
140
Why do capillaries have permeable walls?
So substances can diffuse in and out.
141
What do the capillaries do? (2)
Supply food and oxygen, and take away waste like carbon dioxide.
142
Describe the walls of the capillaries.
Only one cell thick
143
Why is it useful for capillaries to have one cell thick walls?
This increases the rate of diffusion by decreasing the distance over which it occurs.
144
Why do the vein walls not have walls as thick as the artery walls?
The blood is at low pressure
145
Where do the capillaries join up to?
Eventually join up to form veins.
146
Describe the pressure in the veins.
The blood is at low pressure.
147
What do veins have over the arteries?
A bigger lumen
148
Why is it useful for the veins to have a bigger lumen?
To help the blood flow despite the lower pressure.
149
What do veins have?
Valves to help keep the blood flowing in the right direction.
150
What does the coronary artery do?
Coronary arteries branch off the aorta and surround the heart. making sure that it gets all the oxygenated blood it needs.
151
Give the job of the red blood cell.
To carry oxygen from the lungs to all the cells in the body.
152
Give the shape of the red blood cell.
Biconcave disc
153
What is useful about the shape of the red blood cell?
It gives a large SA for absorbing oxygen.
154
Why don't the red blood cells have a nucleus?
It allows them to have more room to carry oxygen.
155
What do red blood cells contain?
A red pigment called haemoglobin.
156
What does haemoglobin do in the lungs?
It binds to oxygen to form oxyhaemoglobin.
157
What does oxyhaemoglobin do in body tissues?
It splits up into haemoglobin and oxygen, to release oxygen to the cells.
158
What is phagocytosis?
It is when white blood cells engulf unwelcome microorganisms and digest them.
159
What are white blood cells able to produce? (2)
1. Antibodies
| 2. Antitoxins
160
What are antibodies able to do?
Fight against microorganisms.
161
What are antitoxins able to do?
Neutralise any toxins produced by the microorganisms.
162
What is the difference between a white blood cell and a red blood cell?
1. White blood cells have a nucleus.
| 2. Red blood cells don't have a nucleus.
163
What are platelets?
Small fragments of cells.
164
True or false, does a platelet contain a nucleus.
False
165
What does lack of platelets cause?
Excessive bleeding and bruising.
166
What is the function of platelets?
To help the blood clot at a wound.
167
Why is it necessary to clot a wound?
1. To stop all your blood pouring out
| 2. To stop microorganisms getting in
168
What is a plasma?
A pale straw- coloured liquid which carries just about everything in blood.
169
List 3 things a plasma can carry (part 1)
1. Red and white blood cells and platelets
2. Hormones
3. Proteins
170
List 3 things a plasma can carry (part 2).
1. CO₂ from the organs to the lungs
2. Urea from the liver to the kidneys
3. Antibodies and antitoxins produced by the white blood cells
171
List one thing a plasma can carry (part 3)
Nutrients like glucose and amino acids (soluble products of digestion which are absorbed from the gut and taken to the cells of the body).
172
What is coronary heart disease?
It is when the coronary arteries that supply the blood to the muscles of the heart get blocked by layers of fatty material building up.
173
What does coronary heart disease cause?
It 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.
174
What are stents?
They are tubes that are inserted inside arteries.
175
What are stents used for?
To keep the arteries open, making sure blood can pass through to the heart muscles. This keeps the person's heart beating.
176
Give an advantage of a stent. (1)
It lowers the risk of a heart attack in people with coronary heart disease.
177
Give an advantage of stent (2).
They are effective for a long time and the recovery time from the surgery is relatively quick.
178
Give a disadvantage of stents (1).
There is a risk of complications during the operation (e.g. heart attack) and a risk of infection from surgery.
179
Give a disadvantage of stents (2).
Risk of patients developing a blood clot near the stent- this is called thrombosis.
180
What is cholesterol?
It is an essential lipid that your body produces and needs to function properly.
181
Give 2 names of too much cholesterol.
1. LDL cholesterol
| 2. "bad" cholesterol
182
What can too much cholesterol cause?
Health problems
183
What can too much of the "bad cholesterol" cause in the bloodstream?
Fatty deposits to form inside arteries, which can lead to coronary heart disease.
184
What are statins?
They are drugs that can reduce the amount of 'bad' cholesterol present in the bloodstream. This slows down the rate of fatty deposits forming.
185
Give an advantage of statin. (1)
Statins can reduce the risk of strokes, coronary heart disease and heart attacks.
186
Give an advantage of statin (2).
It can increase the amount of beneficial type of cholesterol in your bloodstream. This type can remove 'bad' cholesterol from the blood.
187
Give 2 names for beneficial cholesterol.
1. HDL cholesterol
| 2. 'Good' cholesterol
188
Give an advantage of statin (3).
Some studies suggest that statins may also help prevent some other diseases.
189
Give a disadvantage of statin (1).
They are a long-term drug that must be taken regularly. There's the risk that someone could forget to take them.
190
Give a disadvantage of statin (2).
They 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.
191
Give a disadvantage of statin (3).
The effect of statins isn't instant. It takes time for their effect to kick in.
192
What will the doctor perform if a patient has heart failure?
A heart transplant (or heart and lung transplant if the lungs also also diseased) using donor organs from people who have recently died.
193
What will doctors do if the organs aren't available right away?
Doctors may fit an artificial heart.
194
What is an artificial heart?
They are mechanical devices that pump blood for a person whose own heart has failed.
195
What is the purpose of an artificial heart? (1)
They usually only 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.
196
What is the purpose of an artificial heart? (2)
In some cases though they're used as a permanent fix, which reduces the need for a donor heart.
197
Give an advantage of artificial hearts.
They're less likely to be rejected by the body's immune system than a donor heart.
198
Why are artificial hearts less likely to be rejected by the patients body?
They're made from metals or plastics, so the body doesn't recognise them as 'foreign' and attack in the same way as it does with living tissue.
199
Give a disadvantage of an artificial heart. (1)
Surgery to fit an artificial heart can lead to bleeding and infection.
200
Give a disadvantage of an artificial heart. (2)
An artificial heart don't work as well as healthy natural ones- parts of the heart could wear out or the electrical motor could fail.
201
Give a disadvantage of an artificial heart. (3)
Blood doesn't flow through artificial hearts as smoothly, which can cause blood clots and lead to strokes.
202
What does the patient do if the blood doesn't flow through artificial hearts as smoothly?
The patient has to take drugs to thin their blood and make sure this doesn't happen, which can cause problems with bleeding if they're hurt in an accident.
203
How can valves be damaged or weakened in the heart?
By heart attacks, infection or old age.
204
What can damage on a valve cause? (1)
It may cause the valve tissue to stiffen, so it won't open properly.
205
What can damage on a valve cause? (2)
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.
206
How can severe valve damage be treated?
By replacing the valve.
207
Where can you get replacement valves?
It can be 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.
208
What is the problem with fitting an artificial valve?
There can still be problems with blood clots.
209
Give another function of an artificial heart.
It is a blood substitute, e.g. a salt solution ("saline"), which is used to replace the lost volume of blood.
210
Give an advantage of an artificial heart. (2)
It's safe (if no air bubbles get into the blood) and can keep people alive even if they lose 2/3 of their red blood cells.
211
What is health?
It is the state of physical and mental wellbeing.
212
What is responsible for ill health?
Diseases
213
What are communicable diseases?
They are those that can spread from person to person or between animals and people.
214
What are communicable diseases caused by?
Bacteria, viruses, parasites and fungi.
215
What are communicable diseases sometimes described as?
Contagious or infectious diseases
216
Give 2 examples of communicable diseases.
Measles and malaria
217
What are non-communicable diseases?
They are those that cannot spread between people or between animals and people.
218
Give 3 examples of non-communicable diseases.
1. Asthma
2. Cancer
3. Coronary heart disease
219
What is the problem with non-communicable diseases?
They generally last for a long time and get worse slowly.
220
Why are communicable diseases (e.g. influenza virus) more prone to people with problems with their immune system?
Their body is less likely to be able to defend itself against the pathogen that causes the disease.
221
How can some types of cancer be triggered?
By infection by certain viruses.
222
How can a mental health issue such as depression be triggered?
When someone is suffering from severe physical health problems.
223
Give a factor that can affect your health. (1)
A poor diet can affect your physical and mental health.
224
Give a factor that can affect your health. (2)
The stress you are under.
225
Give a factor that can affect your health. (3)
Your life situation
226
Give examples of how your life situation affects your health. (1)
Whether you have easy access to medicine to treat illness.
227
Give examples of how your life situation affects your health. (2)
Whether you have access to things that can prevent you from getting ill in the first place.`
228
What are risk factors?
Risk factors are linked to an increased rate of a disease. They don't guarantee someone will get the disease.
229
Give 2 ways in which risk factors can be a part of.
1. Aspects of a person’s lifestyle
| 2. Substances in the person’s body or environment.
230
What are the different impacts of lifestyle factors can have?
Locally, nationally and globally.
231
What does smoking cause?
Cardiovascular disease, lung disease and lung cancer.
232
What does smoking do to your body?
It damages the walls of arteries and the cells in the lining of the lungs.
233
What does obesity cause?
Type 2 diabetes
234
How does obesity 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.
235
What does drinking too much alcohol cause?
Liver disease
236
What part of the body does drinking too much alcohol affect?
Brain function
237
What damage does drinking too much alcohol do to your body?
It can damage the nerve cells in the brain, causing the brain to lose volume.
238
What are the problems of smoking when pregnant?
It causes lots of health problems for the unborn baby.
239
What can cause cancer?
Exposure to certain substances or radiation.
240
Give the name for things that cause cancer.
Carcinogens
241
Give an example of carcinogen.
Ionising radiation (e.g. from X- rays)
242
What affect do communicable diseases have on the lives of people?
They may have a lower quality of life or a shorter lifespan.
243
Discuss about the financial cost of treating communicable diseases.
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.
244
Describe the effect communicable diseases have on families. (cost)
Families may have to move or adapt their family to help a family member with a disease, which can be costly.
245
What affect do communicable diseases have on the working force?
If a family member with the disease has to give up work or dies, the family's income will be reduced. A reduction of people able to work can also affect a country's economy.
246
What are plants made of?
Organs like stems, roots and leaves.
247
How are organ systems made in plants?
Plant organs work together to make organ systems.
248
Give 5 examples of tissues in a plant.
1. Epidermal tissue
2. Palisade mesophyll tissue
3. Spongy mesophyll tissue
4. Xylem and phloem
5. Meristem tissue
249
Give the function of an epidermal tissue.
This covers the whole plant.
250
Give the function of palisade mesophyll tissue.
This is the part of the leaf where most photosynthesis happens.
251
Give the function of spongy mesophyll tissue.
This is also in the leaf, and contains big air spaces to allow gases to diffuse in and out of cells.
252
Give the function of xylem and phloem.
They transport things like water, mineral ions and food around the plant.
253
Give the function of a meristem tissue.
This is found at the growing tips of shoots and roots and is able to differentiate into lots of different types of plant cell, allowing the plant to grow.
254
What do leaves contain?
Epidermal, mesophyll, xylem and phloem tissues.
255
What is the upper epidermis?
It is transparent so that light can pass through it to the palisade layer.
256
What is the palisade layer?
It has lots of chloroplasts. This means that they're near the top of the leaf where they can get the most light.
257
What does the xylem and phloem tissue do? (1)
They form a network of vascular bundles, which deliver water and other nutrients to the entire leaf and take away the glucose produced by photosynthesis.
258
What does the xylem and phloem tissue do? (2)
They also help the structure.
259
What are the tissues of the leaves adapted to?
They are adapted for efficient gas exchange.
260
What is the lower epidermis full of?
It is full of little holes called stomata, which let CO₂ diffuse directly into the leaf.
261
What is the opening and closing of stomata controlled by?
Guard cells in response to environmental conditions.
262
What do the air spaces in the spongy mesophyll tissue increase?
The rate of diffusion of gases.
263
What are phloem tubes made of and what is it used for?
Columns of elongated living cells with small pores to allow cell sap to flow through.
264
Give the function of phloem tubes (translocation).
They 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.
265
Describe the direction of transport within phloem tubes.
The transport goes in both directions.
266
What are xylem cells made of?
Dead cells joined end to end with no walls between them and a hole down the middle.
267
How are xylem tubes strengthened?
They're strengthened with a material called ligin.
268
Give the function of xylem tubes.
They carry water and mineral ions from the roots to the stems and leaves.
269
What is the transpiration stream?
It is the movement of water from the roots, through the xylem and out of the leaves.
270
What is transpiration caused by?
The evaporation and diffusion of water from a plant's surface.
271
Where does most transpiration occur?
At the leaves
272
What does evaporation from the leaves create?
A slight shortage of water in the leaf.
273
How is there a constant transpiration stream of water through the plant?
More water is drawn up from the rest of the plant through the xylem vessels to replace it. This in turn means more water is drawn up from the roots.
274
What is transpiration described as?
A side effect of the way leaves are adapted for photosynthesis.
275
How is water able to escape from the leaves through the stomata by diffusion?
There's more water inside the plant than in the air outside.
276
Give 4 ways to affect the transpiration rate.
1. Light intensity
2. Temperature
3. Air flow
4. Humidity
277
How can the rate of transpiration be increased by light intensity?
The brighter the light, the greater the transpiration rate.
278
How can the rate of transpiration be increased by temperature?
The warmer it is, the faster transpiration happens.
279
How can the rate of transpiration be increased by air flow?
The better the air flow around a leaf (e.g. stronger wind), the greater the transpiration rate.
280
How can the rate of transpiration be increased by humidity?
The drier the air around a leaf, the faster transpiration happens.
281
Describe what the leaf does if it is dark (1).
Stomata begin to close as it gets darker.
282
Describe what the leaf does if it is dark (2).
Photosynthesis can't happen in the dark, so they don't need to be open to let CO₂ in.
283
Describe what the leaf does if it is dark (3)
When the stomata care closed, very little water can escape.
284
How does increasing the temp. increase the rate of transpiration?
When it's warm the water particles have more energy to evaporate and diffuse out of the stomata.
285
Describe what happens 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 conc. of water particles outside the leaf as well as inside it, so diffusion doesn't happen as quickly.
286
Describe what happens if air flow around a leaf is good.
The water vapour is swept away from an area of higher conc. to an area of lower conc.
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When does diffusion happen the fastest?
If there's a really high conc. in one place, and a really low conc. in the other.
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What happens if the air is humid?
There's a lot of water in it already, so there's not much of difference between the inside and the outside of the leaf.
289
How can you estimate the rate of transpiration?
By measuring the uptake of water by a plant.
290
How are you able to estimate the rate of transpiration by just measuring the uptake of water?
You can assume that water uptake by the plant is directly related to water loss by the leaves (transpiration).
291
Describe the shape of a guard cell.
They have a kidney shape.
292
Give the function of a guard cell.
It opens and closes the stomata in a leaf.
293
What happens if the plant has lots of water?
When the plant has lots of water the guard cells fill with it and go plump and turgid. This makes the stomata open.
294
What happens when the stomata is open?
Gases can be exchanged for photosynthesis.
295
What happens when the plant is short of water?
The guard cells lose water and become flaccid, making the stomata close.
296
What happens when the stomata is closed?
This helps stop too much water vapour escaping.
297
How are guard cells able to open and close?
Due to thin outer walls and thickened inner walls.
298
How are plants able to save water without losing out on photosynthesis?
Guard cells are sensitive to light and close at night.
299
True or false, you can find more stomata on the undersides of leaves than on the top.
True
300
Describe the lower surface of a plant.
It is shaded and cooler- so less water is lost through the stomata than if they were on the upper surface.
301
What are guard cells adapted to?
Gas exchange and controlling water loss within a lieaf.
