PAPER 1 ็ถใ Flashcards
(345 cards)
1
Q
What is the target cell for glucagon?
A
Hepatocytes
2
Q
What is the second messenger for glucagon?
A
cAMP
3
Q
What 3 effects does glucagon have on its target cells?
A
Glycogenolysis, increased rate of fatty acid respiration, gluconeogenesis
4
Q
What is glycogenolysis?
A
What is glycogenolysis?
5
Q
What is gluconeogenesis?
A
Conversion of amino acids and lipids into glucose.
6
Q
What is meant by describing insulin and glucagon as antagonistic hormones?
A
They have opposite effects on blood glucose concentration.
7
Q
How is negative fedback involved in the control of blood glucose levels in the blood?
A
The hormones are antagonistic, having the opposite effects on the blood glucose concentration. High glucose, inslin released to bring down the concentration, low glucose, glycogen release to increase concentration
8
Q
At normal blood glucose levels, how do beta cells stop releasing insulin?
A
potassium channels of beta cells are open and K+ cells constantly diffuse out of cell to maintain a -70mV across the cell membrane
9
Q
How do beta cells detect a change in glucose level to release insulin?
A
At high BGL, glucose enters beta cells by glucose transporters, which is metabolised to make ATP โ> ATP binds to potassium channels and closes them, stopping the diffusion of K+ ions out of cells, causing the membrane potential difference to drop to -30mV (depolarisation) โ> voltage-gated calcium ion channels open, Ca2+ influx causes secretory vesicles to release insulin by exocytosis
10
Q
What two protein channels are involved in the release of insulin from beta cells?
A
ATP-sensitive potassium channels + voltage-gated calcium channels
11
Q
What condition is caused by a long period below the normal blood glucose concentration?
A
Hypoglycaemia
12
Q
What are the symptoms of mild hypoglycaemia?
A
Seizures, unconsciousness, due to impairment of the brain activity
13
Q
What condition is caused by a long period above the normal blood glucose concentration?
A
What condition is caused by a long period above the normal blood glucose concentration?
14
Q
What is the symptom of hyperglycaemia?
A
Organ damage
15
Q
Above what blood glucose concentration is considered a diagnosis for diabetes mellitus?
A
7 mmol dm-3
16
Q
What is the cause of type 1 diabetes?
A
An autoimmune disease where the immune system destroys the beta cells of the pancreas.
17
Q
What is the cause of type 2 diabetes?
A
Receptors on the surface of insulin target cells become less responsive to insulin.
18
Q
What are the 3 risk factors of early onset of type 2 diabetes?
A
Obesity, lack of regular exercise, diet high in sugar
19
Q
What are the 5 possible treatments for type 1 diabetes?
A
Insulin injections, insulin pump, islet cell transplantation, pancreas transplant, stem cells
20
Q
What is the main treatment for type 2 diabetes?
A
Regulate carbohydrate intake, increase exercise levels, take drugs that stimulate insulin production/slow down rate of glucose absorption
21
Q
WHat are the advantages of using insulin from genetically modified bacteria?
A
An exact copy of human insulin so more effective, less chance of developing tolerance, less chance of rejection due to immune response, lower risk of infection, easier to manufacture to demand and less moral objection to production in bacteria to animals
22
Q
What is the โfight or flightโ response?
A
Detecting a threat to survival leading to physiological changes to prepare for a responce
23
Q
What is the survival value of pupils dilating?
A
Allows more light to enter the eyes making the retina more sensitive.
24
Q
What is the survival value of increasing the blood glucose levels?
A
Energy supplied for muscular contraction
25
What is the survival value of increasing ventilation rate and depth?
Increases gaseous exchange so that oxygen enters the blood to supply aerobic respiration
26
What is the survival value to the heart rate and blood pressure increasing?
Increases the rate of blood flow to deliver more oxygen and glucose to the muscles and to remove carbon dioxide and other toxins
27
Where is the 'flight or fight' response coordinated?
Cerebrum
28
How is the 'fight or flight' response coordinated?
Receptor input to the sensory centres in the cerebrum, passing signals to associated centres and to the hypothalamus if a threat is detected.
29
What is the role of the hypothalamus in respose to a threat?
Increases activity in the sympathetic nervous system and stimulated release of hormones form anterior pituitary gland
30
What 2 effects result from the hypothalmus activating the sympathetic nervous system?
Impulses activate gland and smooth muscle and activate adrenal medulla secreteing adrenaline
31
What happens next once adrenaline binds to the receptor on the cell surface?
Activates adenylyl cyclase to convert ATP to cAMP
32
What effects are caused on the cell by having more cAMP?
cAMP activates protein kinases to phosphorylate and activate other enzymes to bring about different effects (eg. convert glycogen into glucose)
33
What is the role of cAMP in the action of adrenaline on a cell?
Second messenger
34
What part of the medulla oblongata controls heart rate?
Cardiovascular centre
35
Name the two types of receptors that detect stimuli to affect heart rate.
Baroreceptors (blood pressure) + chemoreceptor (chemical in blood)
36
What are 2 stimuli that would lead to an increase in heart rate?
low blood pH, low blood pressure
37
What is a stimulus that would lead to a decrease in heart rate?
High blood pressure
38
What neurotransmitter is released at the SAN to increase the heart rate?
Adrenaline / Noradrenaline
39
What neurotransmitter is released at the SAN to reduce the heart rate?
Acetylcholine
40
What effect could sensory input to the cardivascular centre from stretch receptors in muscles?
Extra oxygen may be needed for movement increasing the heart rate
41
What do chemoreceptors in the carotid arteries and aorta do?
Monitor the pH of the blood
42
What is negative feedback?
A response that is opposite to the stimulus, returning conditions back to the optimum.
43
What is positive feedback?
A response that increases the stimulus, taking conditions further away from the optimum.
44
What is the difference between endotherms and ectotherms?
- Endotherms generate own heat by metabolic reactions
- Ectotherms relies on environment to control body temp
45
What is an ectotherm?
An organism that is unable to control its body temperature and is reliant on external sources of heat.
46
What is an endotherm?
An organism that controls its body temperature in a narrow range using physiological or behavioural adaptations.
47
What is an exergonic chemical reaction?
A chemical reaction that releases thermal energy.
48
Name 5 physiological responses in an endotherm to an increase in body temperature.
Sweating, pilorelaxation, vasodilation, reduced liver metabolism, panting
49
Name 4 physiological responses in an endotherm to an decrease in body temperature.
Piloerection, vasoconstriction, increased liver metabolism, shivering
50
What is vasodilation?
Relaxation of smooth muscle to widen arterioles and allow blood flow close to the skin's surface.
51
What is vasoconstriction?
Contraction of smooth muscle to narrow arterioles and restrict blood flow close to the skin's surface.
52
What is pilorelaxation?
Relaxation of the skin's hair erector muscles so hair lies flat.
53
What is piloerection?
Contraction of the skin's hair erector muscles so hair stands erect.
54
Name 4 behavioural responses in endotherms and ectotherms to an increase in body temperature.
Seek shade, reduce surface area, inactivity, wet skin
55
Name 4 behavioural responses in endotherms and ectotherms to an decrease in body temperature.
Seek sunlight, increase surface area, activity, keep dry
56
What are 3 advantages of being ectothermic that are disadvantages of being endothermic?
Ectotherms can: use less energy from food for respiration, use more energy from food for growth, survive long periods without food
57
What are 3 advantages of being endothermic that are disadvantages of being ectothermic?
Endotherms can: remain active in low temperatures, inhabit colder parts of the planet, maintain a constant internal temperature
58
What is excretion?
The removal of metabolic waste from the body.
59
Name 3 excretory products.
Carbon dioxide, urea, bile pigments
60
What are the 4 main excretory organs?
Lungs, liver, kidneys, skin
61
What is the effect on the blood of an increase in carbon dioxide concentration?
Decrease in pH.
62
What is the response to an increase in carbon dioxide concentration in the blood?
Increase in breathing rate.
63
What is the name for the basic functional unit of the liver?
Lobules
64
What is another name for liver cells?
hepatocytes
65
What are the 4 vessels associated with the liver?
Hepatic vein, hepatic portal vein, hepatic artery, bile duct
66
Which liver vessel(s) is intra-lobular?
Hepatic vein
67
Which liver vessel(s) is inter-lobular?
Hepatic portal vein, hepatic artery, bile duct
68
What are the chambers in the lobules through which blood from the hepatic portal vein and hepatic artery pass?
Sinusoids
69
What are the chambers in the lobules through which bile is transported to the bile duct?
Canaliculi
70
What are the resident macrophages called in the liver?
Kupffer cells
71
What is the function of a Kupffer cell?
Break down and recycle old red blood cells.
72
Name three key functions of the liver.
- carbohydrate metabolism
- deamination of excess amino acids
- detoxification
73
What is deamination?
Removal of the amine group from an amino acid.
74
What is transamination?
Conversion of one amino acid into another
75
Why is transamination important?
To make essential amino acids that are not normally in our diet
76
What is the amine group converted into after deamination?
Ammonia (then urea)
77
Ammonia is converted to urea by โฆโฆโฆโฆโฆโฆโฆโฆโฆ
ornithine cycle
78
What is the word equation for the ornithine cycle?
Ammonia + carbon dioxide โ urea + water
79
Name two enzymes found in hepatocytes that are involved in detoxification.
Catalase; Alcohol dehydrogenase
80
Name the two products of the breakdown of hydrogen peroxide.
Oxygen and water
81
How is the liver involved in regulating blood glucose level?
Interacts with insulin and glucagon to convert between glucose and glycogen
82
Where is bile stored?
Gall bladder
83
What is the function of bile?
Emulsification - increases surface area for more lipase to work on --> speeds up lipid digestion
84
What are the two key functions of the kidneys?
ultrafiltration
+ selective reabsorption
85
What structures of the kidneys are involved in ultrafiltration?
Glomerulus
+ Bowmanโs capsule
86
What is the importance of selective reabsorption?
Get the useful substances back into the body
87
What are the 3 vessels associated with the kidney?
Renal artery, renal vein, ureter
88
What are the 3 regions of the kidney (from outside to inside)?
Cortex, medulla, pelvis
89
What are the kidney tubules called?
Nephrons
90
What are the 5 components of the nephron?
Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct
91
What is the name for the knot of capillaries surrounded by the Bowman's capsule?
Glomerulus
92
What arteriole enters the glomerulus?
Afferent
93
What arteriole exits the glomerulus?
Efferent
94
What is the difference in the structure of the afferent and efferent arterioles?
Afferent has a wider lumen / Efferent has a narrower lumen.
95
What is ultrafiltration?
The pushing of fluid out of the glomerulus into the Bowman's capsule.
96
What are the 3 layers through which ultrafiltration occurs?
Endothelium of capillary, basement membrane, podocytes (epithelium of Bowman's capsule)
97
What 5 substances are able to pass from the glomerulus into the Bowman's capsule?
Water, amino acids, glucose, urea, mineral ions
98
What 2 substances are unable to pass from the glomerulus into the Bowman's capsule?
Red / white blood cells, plasma proteins
99
Where does selective reabsorption mainly take place in the nephron?
Proximal convoluted tubule
100
What 4 substances are reabsorbed in the proximal convoluted tubule?
Glucose, amino acids, mineral ions, water, vitamins, hormones
101
What are the 5 specialisations of the PCT epithelial cells?
Microvilli on surface in contact with lumen, lumen membrane has many cotransporter proteins, highly folded membrane on surface in contact with capillaries, capillary-facing membrane has many Na+/K+ pumps, many mitochondria
102
What cotransport occurs in the PCT?
Glucose and Na+ from the lumen into the epithelial cells.
103
What are the 2 sections of the loop of Henle called?
Descending limb, ascending limb
104
What substance(s) enter the descending limb of the loop of Henle?
Mineral ions (Na+ and Cl-)
105
What substance(s) leave the descending limb of the loop of Henle?
Water
106
What substance(s) enter the ascending limb of the loop of Henle?
None
107
What substance(s) leave the ascending limb of the loop of Henle?
Mineral ions (Na+ and Cl-)
108
What happens to the water potential of the urine as it passes through the descending limb of the loop of Henle?
Decreases / becomes more negative
109
What happens to the water potential of the urine as it passes through the ascending limb of the loop of Henle?
Increases / becomes less negative
110
What happens to the water potential of the tissue fluid of the medulla towards the bottom of the loop of Henle?
Decreases / becomes more negative
111
What is the hairpin countercurrent multiplier effect in the loop of Henle?
The transfer of mineral ions from the ascending to descending limb creating a water potential gradient between urine and tissue fluid at all points along the loop of Henle.
112
What is the importance of energy in the loop of Henle?
To do active transport to reabsorb Na+ and Cl- in the ascending limb
113
What occurs in the distal convoluted tubule?
Active transport of minerals out of the nephron to further increase the water potential.
114
What happens in the collecting duct?
Reabsorption of water, affected by ADH concentration
115
How does the body lose water?
Urine, sweat, exhaled air, faeces
116
What is osmoregulation?
Control of the blood water potential.
117
What is ADH?
Anti-diuretic hormone
118
What are the target cells of ADH?
Collecting duct epithelial cells
119
What is the effect of ADH on its target cells?
A cascade of enzyme-controlled reactions resulting in vesicles containing aquaporins fusing with the cell surface membrane.
120
What is an aquaporin?
Water permeable channel
121
Where are aquaporins found in cells lining the collecting duct that have not been affected by ADH?
In the membrane of vesicles.
122
Where are aquaporins found in cells lining the collecting duct that have been affected by ADH?
In the cell surface membrane.
123
What receptors detect changes in the water potential of the blood?
Osmoreceptors
124
Where are osmoreceptors found?
Hypothalamus
125
Where is ADH produced?
Hypothalamus
126
Where is ADH released?
Posterior pituitary gland
127
If water needs to be conserved, __________ ADH is secreted, __________ water is reabsorbed and __________ urine is produced.
More, more, less
128
If water does not need to be conserved, __________ ADH is secreted, __________ water is reabsorbed and __________ urine is produced.
Less, less, more
129
If a urine sample contains glucose, what may be a possible diagnosis about the patient?
High blood pressure / kidney failure (problem with selective reabsorption) / Diabetes
130
What is the glomerular filtration rate (GFR)?
A measure of the volume of fluid passing into the nephrons every minute.
131
What are the units used to measure GFR?
cm3 min-1
132
What is considered the normal range for GFR?
90-120 cm3 min-1
133
Below what GFR value is an indication of kidney disease?
60 cm3 min-1
134
What are 5 substances that can be detected in the urine?
Glucose, alcohol, recreational drugs, hCG, anabolic steroids
135
What hormone is detected using a pregnancy-testing kit?
Human chorionic gonadotrophin (hCG)
136
What are monoclonal antibodies?
Antibodies produced by clones of a single plasma cell, usually specific to a single epitope of an antigen.
137
What is the purpose of the control zone on a pregnancy-testing kit?
To determine if the kit is working.
138
What do monoclonal antibodies do in pregnancy testing?
Binds specifically to hCG and to the immobilised antibodies in the test window
139
Why should the pregnancy test be done early in the morning?
Highest concentration - as more water has been reabsorbed overnight, the urine should have the highest concentration of hCG in the morning
140
What methods are used to test for the presence of anabolic steroids in urine?
Mass sepctrometry and gas chromatography
141
What is gas chromatography?
A separation technique used to determine the compounds in a liquid mixture based on their volatility.
142
Why is it necessary to do another test after immunoassay when testing for illegal drugs in urine?
To confirm the presence of the drug
143
What are the 2 most common treatments for kidney failure?
Renal dialysis, kidney transplant
144
What is renal dialysis?
Treatment used to artificially regulate the concentrations of solutes in the blood.
145
What are the 2 types of renal dialysis?
Haemodialysis, peritoneal dialysis
146
What is the membrane used in haemodialysis?
Artificial dialysis membrane
147
What is the membrane used in peritoneal dialysis?
Abdominal (peritoneal) membrane
148
How does the membrane used in haemodialysis determine what substances leave or stay in the blood?
The size of the gaps within the membrane
149
Which process in the kidneys does haemodialysis replace?
Ultrafiltration
150
How should the dialysis fluid be designed? What sort of chemicals and concentrations should be in it?
Should imitate concentrations of solutes in healthy blood/plasma
151
Why is it bad for the dialysis fluid to be pure water?
Lose useful substances due to steep concentration gradient (eg. glucose, vitamins, hormones)
152
What are the 4 main advantages of having a kidney transplant instead of renal dialysis?
Freedom from ongoing treatment, feeling physically fitter, better quality of life, improve self image
153
What are the 4 main disadvantages of having a kidney transplant instead of renal dialysis?
Regular doses of immunosuppressants, requires major surgery, possible rejection, side effects of immunosuppressants
154
State the difference between a tropic and a nastic response.
Tropic - directional; nastic - non-directional
155
Suggest why plant growth regulators are called hormones despite not being produced in endocrine glands.
Because, like animal hormones, they are chemical messengers that can be transported away from their site of manufacture to act on other parts of the plant. They also act on specific receptors
156
Explain why only certain tissues in a plant respond to a particular plant hormone.
Only the target tissues will have the necessary complementary-shaped receptors on their cell surface membranes to which the particular hormone molecule can bind.
157
State three functions of auxins.
Promotes cell elongation, prevents leaf fall (abscission), maintains apical dominance, inhibits ethene release
158
State three functions of cytokinins.
Promote cell division, delay leaf senescence, overcome apical dominance
159
State two functions of gibberellins.
Promote stem elongation, promote seed germination,
160
State two functions of ethene.
Causes fruit ripening, promotes leaf abscission
161
State two functions of abscisic acid.
Inhibits seed germination (maintains dormancy), stimulate stomatal closure in times of water stress, stimulate production of antifreeze molecules in cold weather
162
Describe the synergistic action of auxin and gibberellin.
Auxin and gibberellin work together to promote stem elongation (giberellins have a greater effect on this)
163
Describe the antagonistic action of auxin and ethene.
Auxin inhibits leaf abscission, ethene promotes leaf abscission
164
Describe the antagonistic action of gibberellin and abscisic acid.
Gibberellins promote seed germination, ABA inhibits seed germination
165
Describe the antagonistic action of auxin and cytokinin.
Auxin maintains apical dominance, cytokinin overcomes apical dominance
166
Describe how gibberellins stimulate seed germination.
Seed absorbs water activating gibberellin production; enzymes like amylase and protease produced to break down food stores; these food stores are respired to produce ATP for growth of a root and shoot
167
State a specific example of an auxin.
IAA
168
Describe how auxins promote cell elongation.
1.) Auxin molecules are produced at the tip and diffuse down the shoot; 2.) Auxin binds to specific receptors on cell surface membranes; 3.) Protons actively pumped into cellulose cell walls; pH falls to about 5 in cell wall providing an optimum pH for expansins; 4.) Expansins break cross links and hydrogen bonds between cellulose molecules; 5.) Lower pressure in cell wall compared to cell means water moves into cell wall and it expands and stretches; 5.) as hormone levels fall further down the shoot, pH rises and expansins denatured; 6.) cellulose cross linking can now occur and cell wall becomes rigid
169
Describe the contributions of auxins, cytokinins and abscisic acid to apical dominance.
High auxin levels --> high abscisic acid levels --> low cytokinins in lateral buds --> lateral bud growth inhibited (apical dominance maintained)โฆlow auxin levels (if shoot tip removed) --> low abscisic acid levels --> higher cytokinin levels in lateral buds --> lateral bud growth occurs (apical dominance overcome)
170
Explain how roots behave in response to particular levels of auxin.
Low auxin concentrations promote root growth; high concentrations of auxin inhibit root growth
171
Where does IAA accumulate when a plant is exposed to unilateral light?.
The shaded side
172
What causes leaf loss in deciduous plants?
when the amount of glucose needed by the plant for respiration to maintain the leaves is less than the amount of glucose produced by photosynthesis
173
What is the term given to a plants' sensitivity to a lack of light?
photoperiodism
174
What are the light-sensitive pigments that enables photoperiodism to happen?
phytochromes
175
What is the abscission?
Leaf fall
176
Describe the process of abscission.
Falling light levels result in falling conc. of auxin. Leaves respond by producing ethene. Ethene stimulates production of enzymes that digest and weaken cells at the base of the leaf stalk. vascular bundles are sealed off and a layer of fat is deposited. Cells in separation zone swell by retaining water. This strains weakened separation zone. Wind and low temps also help to separate leaf from plant.
177
How do plants avoid freezing?
solutes in cytoplasm reduce the freezing point. Some produce sugars, polysaccharides, amino acids and proteins to act as antifreeze
178
why do plants need to prevent their cells from freezing?
their cell membranes would be ruptured and they would die.
179
What are the 2 main abiotic stresses that plants must adapt to?
Heat and water availability
180
What effect does stomatal opening have on heat stress on a plant?
It cools the plant/ reduces the temperature. Water leaves the stomata and evaporates, reducing the temperature of the plant.
181
What effect does ABA have on the stomata?
ABA (from leaf and root cells) causes stomatal closing by activating changes in ionic conc of guard cells, reducing water potential and turgor of cells and closing stomata
182
State three chemical defences against herbivory (attack by insects).
Tannins, alkaloids, Terpenoids
183
State three physical defences against herbivory.
thorns, barbs, spikes, spiny leaves, fibrous and inedible tissue, hairy leaves, stings
184
How do tannins prevent herbivory?
bitter taste to deter animals and toxic to insects (inactivate digestive enzymes in insect saliva)
185
How do alkaloids prevent herbivory?
bitter tasting and sometimes poisonous
186
How do tannins prevent herbivory?
toxins to insects and fungi
187
What is the name for a chemical made by an organism which affects the behaviour of other members of the same species?
Pheromones
188
Plants do not have pheromones, what do they have instead?
Volatile Organic Chemicals (VOCs). produced by plants, which act between themselves and other organisms
189
Give an example of a plant that produces a VOC and describe its' action.
Cabbages, under attack from cabbage white butterfly caterpillars, produce VOC's to attract the wasp cotesia glomerata. wasp lays eggs in caterpillars eggs, killing them. The VOC's deter the femal cwb from laying more eggs on the plant. Apple trees, when attacked by spider mites, produce VOC's to attract predators of the mites. Wheat produces VOC's, when attacked by aphids, to deter other aphids
190
How does the plant, mimosa pudica protect itself against herbivory?
contains alkaloids and stem has sharp prickles, but if leaves are touched, they fold down and collapse. dislodges insects and scares off larger animals. Caused by movement of potassium ions and changes in water potential of the cells.
191
Describe the functions of positive phototropism and positive geotropism.
Positive phototropism - plant shoots grow towards light which enables them to carry out the light dependent reaction of photosynthesis. Positive geotropism - roots grow downwards into the soil, giving them anchorage and enabling them to obtain water and mineral ions
192
What will happen if a shoot is grown in light, shining from one side?
It will grow towards the light/ positive phototropism
193
If a shoot is exposed to light from one side, where will auxin be found within the shoot?
There will be less auxin on the light side and a greater concentration of auxin on the shady side. Auxin migrates laterally away from the light.
194
What effect does auxin have on the cells in a shoot?
it causes cell elongation and growth on the dark side so the shoot bends away from the shaded side and towards the light
195
What is etiolation?
When plants are grown in the dark or partial darkness, producing rapid growth upwards. plants are tall, thin and pale.
196
Which hormones cause longer internodes in plants grown in the dark?
Gibberellins
197
What slow-rotating piece of equipment can be used to demonstrate geotropism in the lab?
Clinostat
198
What would you expect to observe if germinating beans are grown on a clinostat over a a few days?
The roots will curl as they try to grown 'downwards'
199
What would you expect to observe if a potted plant shoot is grown on a clinostat over a a few days?
The shoot will grow horizontally outwards from the pot.
200
Which plant hormone is involved in fruit ripening?
Ethene
201
Which plant hormone is involved in encouraging root growth?
Auxins
202
Which plant hormone(s) is/are involved in delaying senescence?
In leaves - cytokinins; in citrus fruits - gibberellins
203
Which plant hormone is involved in preventing the ageing of ripened fruit?
Cytokinins
204
What hormone is used in rooting powder?
Auxin
205
What are climacteric fruits?
Fruits that continue to ripen after harvesting e.g. bananas, avocados, tomatoes, mangoes
206
Why are climacteric fruits harvested before they are ripe?
The unripe fruit is hard and much less easily damaged during transport than the ripe fruit.
207
How are auxins used as weedkillers?
they cause rapid and unsustainable growth in the dicot weeds so they die
208
Is photosynthesis endothermic or exothermic? What does that mean?
Endothermic - overall reaction takes in energy
209
State the overall chemical equation of photosynthesis.
6CO2 + 6H2O --> C6H12O6 + 6O2
210
What is chemiosmosis?
Movement (diffusion) of protons across ATP synthase down the electrochemical gradient to generate ATP
211
In chemiosmosis, where does the energy to pump protons come from?
Energy given off by an electron passing down the first electron transport chain in the light-dependent reaction
212
Chemiosmosis allows the transformation of ADP into ATP. This process in photosynthesis is known as?
Photophosphorylation
213
During photosynthesis, what is pumped across the membrane and into the thylakoid space of the chloroplast?
Hydrogen ions
214
What pumps the hydrogen ions into the thylakoid space?
A cytochrome complex (electron carrier)
215
Where does chemiosmosis occur?
Along the membrane
216
What is grana?
Stacks of thylakoids that contain photosynthetic pigments
217
What is the stroma and its function?
The fluid enclosed in the chloroplast; Site of light-independent stage
218
What is the structure that connects grana together?
Intergranal lamella
219
Describe the structure of a photosystem
A light-harvesting complex that channels light towards a reaction centre (containing a primary pigment called chlorophyll a); accessory pigments channel photons towards the reaction centre
220
Name one primary pigment and 3 accessory pigments
Primary - chlorophyll A; accessory - xanthophylls, carotenoids, chlorophyll b
221
Describe the differences between photosystem I and photosystem II
PSI contains chlorophyll a that absorbs light at a peak of 700nm (P700). PSII contains chlorophyll a that absorbs light at a peak of 680 nm. Electrons are excited to a higher energy level in PSI than PSII
222
Describe the light absorption of carotenoids, xanthophylls and chlorophylls
Carotenoids absorb blue light; xanthophylls absorb blue and green light; chlorophylls absorb blue and red light
223
In which part of the chloroplast does the light-dependent reaction take place?
Thylakoid membrane
224
In which part of the chloroplast does the light-independent reaction take place
Stroma
225
Suggest why the Rf values of some pigments show a range rather than a single figure
There are different types of these, with slightly different molecular masses/sizes of molecules/solubilities in the solvent
226
Rf values for the different pigments differ according to the solvent used. Suggest why this is the case
The molecules of pigment will have different solubilities in different solvents.
227
What 4 processes occur in the light-dependent reaction?
Light harvesting at the photosystems; photolysis of water; photophosphorylation (production of ATP in the presence of light); formation of reduced NADP
228
Outline the role of water in photosynthesis
Electron donor; source of protons/hydrogen ions; source of by-product, oxygen; keeps cells turgid so they can function (all metabolic reactions need to be in solution).
229
Suggest why a lack of iron in soil may reduce growth in plants
Iron is needed for electron carriers in the chain (on thylakoid membranes) and for ferredoxin. A reduction of electron carriers could reduce rate of photosynthesis.
230
What is photolysis and where exactly does it take place?
The enzyme-catalysed splitting of water molecules, in the presence of light. It takes place in PSII on thylakoid membranes of chloroplasts.
231
Describe the differences between non-cyclic and cyclic photophosphorylation
NC - involves PSI and PSII; produces ATP, oxygen and reduced NADP (NADP is final electron acceptor). C - involves PSI only; produces ATP only as electrons are recycled back to PSI and NADP is not reduced
232
Describe how a proton gradient develops between the thylakoid lumen and the stroma
Energy from electrons moving through chain of electron carriers is used to actively pump protons across the thylakoid membrane into the thylakoid lumen
233
Describe the purpose of the proton gradient
Protons can diffuse down their gradient through ATP synthase channels (using proton motive force), causing ADP to combine with inorganic phosphate to form ATP
234
Describe what happens to protons that have moved through ATP synthase
They are accepted along with electrons from the electron transport chain, by NADP. This is facilitated by NADP reductase (NADP has been reduced to NADPH)
235
Describe how an electron moves through the electron transport chain
A photon excites an electron from PSII, the electron rising to a higher energy level and getting accepted by an electron acceptor. This energy level is unstable so the electron moves through a chain of electron carrier proteins, losing energy as it moves (this energy is transferred to pump protons). It is accepted by chlorophyll a in PSI and re-excited by another photon of light to a higher energy level than before.
236
Explain why chloroplasts in guard cells only contain PSI
Produces ATP which actively pumps potassium ions into the cell, lowering the water potential so water follows by osmosis. This causes the guard cell to become turgid and the stoma to open.
237
Describe the differences in the fate of electrons released from chlorophyll in both non-cyclic and cyclic photophosphorylation
Cyclic - pass via electron carriers back to PSI (little ATP generated); Non-cyclic - from PSII, pass via electron transport chain to PSI, PSI electrons accepted by NADP
238
What is RuBisCo and its function?
Ribulose bisphosphate carboxylase/oxidase; an enzyme found in the stroma that catalyses carbon fixation (CO2 + RuBP --> GP)
239
Suggest why there are always only low levels of RuBP in the stroma of chloroplasts
It is being continually regerated and then combined with CO2
240
Describe the role of carbon dioxide in the Calvin cycle
Combines with 5C-RuBP to form a 6C intermediate. This is unstable and so breaks into 2 x 3C-GP molecules. This reaction is catalysed by RuBisCO
241
Describe the conversion of GP into TP in the Calvin cycle
3C-GP is converted into 3C-TP using ATP and the H atom from reduced NADP
242
Describe how RuBP is regenerated in the Calvin cycle
5/6 of TP is converted back into RuBP through reshuffling of the arrangement of carbon atoms. This conversion also uses ATP (RuP --> RuBP)
243
Describe the fate of triose phosphate
1/6 leaves the Calvin cycle and is converted into sucrose, starch, cellulose, amino acids, glycerol, fatty acids, some is respired in glycolysis. The other 5/6 is used to regerate RuBP
244
State 2 products of the light dependent reaction used in the Calvin cycle
ATP and reduced NADP
245
Describe how plants respond to water stress. Explain how this affects their abiity to photosynthesise
Leaves lose more water by transpiration than can be replaced by uptake at roots. Cells lose water/become plasmolysed. Tissues become flaccid. Leaves wilt. Roots are unable to take in water and secrete abscisic acid, which travels in xylem to leaves causing stomata to close to prevent further water vapour loss. Closed stomata reduce gaseous exchange so not enough carbon dioxide for photosynthesis. Plasmolysed cells cannot function as enzymes cannot work. Reduced water availability for photosynthesis โ as source of electrons and protons.
246
Describe the effects of reducing the light intensity on the Calvin cycle
Light dependent reaction cannot occur, so less ATP/NADPH; less GP --> TP; TP levels fall and GP accumulates; if TP levels fall then RuBP cannot be regenerated
247
Describe the effects of reducing carbon dioxide levels in the Calvin cycle
RuBP cannot accept it and RuBP accumulates; GP cannot be made; TP cannot be made
248
Name all three enzymes involved in photosynthesis and their functions.
ATP synthase (allows chemiosmosis to occur to join ADP and Pi together to make ATP); NADP reductase (joins NADP with H+ and e- to make reduced NADP); RuBisCo (catalyses carbon fixation - CO2 + RuBP --> GP)
249
Describe what is meant by the term compensation point
When the rate of photosynthesis is equal to the rate of respiration. This is when there is no net gain or loss of carbohydrate
250
Define 'limiting factor'.
A factor that limits the rate of reaction when in short supply
251
Name three factors that affect photosynthetic rate.
Temperature; Carbon dioxide conc; Light intensity
252
Why does increasing light intensity also increases photosynthetic rate?
More energy absorbed by photosystems to excite electrons, so more electrons undergo ETC to generate proton gradient for more ATP production and reduced NADP production
253
Why does more carbon dioxide increases photosynthetic rate?
Higher rate of carbon fixation at Calvin cycle for more GP and TP production
254
Describe and explain how temperature affects photosynthetic rate.
At lower temp, enzymes are inactive hence low PS rate. As temp increases, enzymes and substrates gain KE and hence higher rate of ESC formation, so higher PS rate. At higher temp, enzymes become denatured hence PS rate decreases.
255
What is ATP synthesised from?
ADP + inorganic phosphate (P)
256
Name three biological processes that require the use of ATP
active transport, endocyctosis, DNA replication
257
Draw a molecule of ATP
Check book
258
What is a catabolic reaction?
Occurs within a cell. Large molecules are broken into smaller molecules.
259
What is an analbbolic reaction?
Small molecules are combined into larger molecules
260
What is glycolysis?
The first stage of respiration, glucose is converted into pyruvate.
261
What is NAD?
A coenzyme (nicotinamide adenine dinucleotide) Reduced NAD carries protons and electrons to the cristae
262
What is phosphorylation in glycolysis?
Where glucose has 2 phosphategroups attached to form hexose bisphosphate using 2 molecules of ATP.
263
What is hexose bisphosphate split into during glycolysis?
2 molecules of triose phosphate
264
What is triose phosphate converted into during the oxidation stage of glycolysis?
Pyruvate
265
How many carbons are found in a molecule of pyruvate?
3
266
Which molecule accepts the hydrogen atoms from triose phosphate when it is oxidised?
NAD
267
What are the products of glycolysis for every molecule of glucose?
2 x pyruvate, 2 molecules of ATP, two reduced NAD
268
What is the net gain of ATP in glycolysis?
2 (four are made but two are used)
269
Why is glycolysis an anaerobic process?
It occurs in the cytoplasm without the need for oxygen
270
What is the cristae?
the inner highly folded mitochondrial membrane
271
What is the mitochondrial matrix?
fluid filled inner part of the mitochondria
272
What is the average length of mitochondrion?
2-5 micromiters
273
Where does the link reaction occur in the mitochondria?
the mitochondrial matrix
274
What is the name of the two coenzymes found in the mitochondria?
NAD & FAD
275
Where is the electron transport chain found in the mitochondria?
The cristae of the inner membrane
276
What is the name of the enzyme found in the cristae of the enzyme that synthesises ATP?
ATPsynthase
277
What is decarboxylation?
removal of a carboxyl group from a substrate molecule
278
What is dehydrogenation?
the removal of a hydrogen atom from a substrate molecule
279
What is substrate level phosphorylation?
production of ATP from ADP and P during glycolysis and the Krebs cycle
280
Why is pyruvate said to be decarboxylated and dehydrogenated during the link reaction?
The pyruvate loses a molecule of carbon dioxide and reduces NAD to become acetyl
281
What does the acetyl group in the link reaction join with before entering the Krebs cycle?
Coenzyme A
282
Explain how 1 molecule of glucose is formed into two molecules of acetyl coenzyme A
Glycolysis then the link reaction summary
283
What molecule enters the Krebs cycle?
Acetyl CoA
284
How many carbons are found in a molecule of acetyl CoA
2
285
What molecule does acetyl CoA join to in the Krebs cycle?
oxaloacetate
286
How many carbons does citrate contain?
6
287
What two molecules combine together to form citrate in the Krebs cycle?
Oxaloacetate and acetyl CoA
288
What happens to citrate in the Krebs cycle?
It is decarboxylated and dehydrogenated into a 5C compound
289
What happens to the 5C compound in the Krebs cycle?
It is decarboxylated and dehydrogenated into a 4C compound
290
Where does substrate level phosphorylation occur in the Krebs cycle?
The 4C molecule combines temporarily with coenzyme A to produce a molecule of ATP
291
What are the products of one turn of the Krebs cycle?
3 reduced NAD, 1 reduced FAD, 2 molecules of CO2 and 1 molecule of ATP
292
What is the final stage of aerobic respiration called?
oxidative phosphorylation
293
Define chemiosmosis
the flow of protons, down their concentration gradient, across a membrane, through channel associated with ATP synthase
294
What is oxidative phosphorylation?
the formation of ATP using energy released from the ETC and in the presence of oxygen.
295
Where does oxidative phosphorylation take place?
in the mitochondria
296
What is the electron transport chain?
A chain of electron carrier proteins that contain an Fe ion. As electrons pass along the chain, some of the enrgy is used to pump protons across the inner mitochondrial membrane.
297
What is the name of the enzyme embedded in the cristae that is involved in oxidative phosphorylation?
ATP synthase
298
Which two coenzymes deliver hydrogen atoms to the ETC?
Reduced NAD & reduced FAD
299
How do reduced NAD & FAD relaese the hydrogen atoms they are carrying at the ETC?
They are reoxidised
300
What happens to the hydrogen atoms released at the ETC?
They are split into protons and electrons
301
When electrons are released at the ETC from reduced NAD and FAD, what is their fate?
They are passed along the chain of electron carriers. They are finally accepted by oxygen which helps to form water.
302
Where are protons pumped into by the ETC?
The intermembrane space
303
What forms when protons are pumped into the intermembrane space?
A proton gradient
304
What is the source of potential energy in the intermembrane space?
The proton gradient accumulates and creates a chemiosmotic potential also known as the proton motive force. The energy is used to genertae ATP.
305
As protons flow from the high concentration inside the intermembrane space, why must they flow through ATP synthase?
The protons cannot easily flow through the lipid bilayer of the mitochondrial membranes.
306
How does the flow of protons cause ATP to be formed?
The protons cause a conformational change in the ATPsynthase which allows ADP and Pi to combine to form ATP.
307
What is the final electron acceptor?
oxygen
308
How is water formed during oxidative phosphorylation?
Oxygen accepts the electrons and combines with protons from chemiosmosis to form water
309
Which stage of photosynthesis also involves chemiosmosis?
Photophosphorylation in the light dependent reaction
310
How many ATP can be formed from a molecule of reduced NAD?
3 ATP (2.5)
311
How many ATP can be formed from a molecule of reduced FAD
2 ATP (1.5)
312
How many molecules of ATP can be formed from glycolysis by 1 molecule of glucose?
2
313
How many molecules of ATP can be formed from the link reaction by 1 molecule of glucose?
0
314
How many molecules of ATP can be formed from the Krebs cycle by 1 molecule of glucose?
2
315
How many molecules of ATP can be formed from oxidative phosphorylation by 1 molecule of glucose?
28
316
What is the total yield of ATP from one molecule of glucose during aerobic respiration?
32
317
Why is the theoretical yield of 32 ATP per glucose molecule rarely achieved?
Some ATP is used, some portons may leak through the mitochondrial membrane
318
Why is the pH of the intermebrane space lower that the mitochondrial matrix and the cytoplasm?
There is an accumulation of protons.
319
What are the two metabolic pathways used by eukaryotic cells to reoxidise NAD
Ethanol fermentation and lactate fermentation
320
Which stage of respiration is the same for both aerobic and anaerobic respiration? Why?
Glycolysis, it occurs in the cytoplasm
321
In ethanol fermentaion, what enzyme decarboxylates pyruvate into ethanal?
pyruvate decarboxylase
322
The enzyme pyruvate decarboxylase converts pyruvate into what during ethanol fermentation in yeast?
ethanal
323
Which enzyme is used to help ethanal accept hydrogen from reduced NAD in ethanol fermentaion in yeast?
ethanol dehydrogenase
324
Why is yeast described as a faculative anaerobe?
It can respire aerobically or anaerobically depending on the environment
325
Write out the two steps involved in ethanol fermentation
1. Pyruvate --> Ethanal + CO2; 2. Ethanal + H+ from reduced NAD --> Ethanol
326
What is the name of the enzyme that allows pyruvate to accept hydrogen from reduced NAD in lactate fermentation
lactate dehydrogenase
327
Write out the equation for formation of lactate in anaerobic respiration in eukaryotic cells
Pyruvate + H+ from reduced NAD --> lactate
328
What is the fate of lactate?
It is moved to the liver where it is eitehr converted back into pyruvate or it is recycled to glucose and oxygen
329
Lactate and ethanol fermentation do not produce any ATP. Suggest how these processes still allow the production of some ATP
Both processes allow glycolysis to continue which has a net gain of 2 ATP
330
What is a respiratory substrate?
an organic substance that can be oxidised by respiration, releasing energy to make ATP
331
How can glycerol be used as a respiratory substrate?
It is converted to triose phosphate and then respired
332
How are fatty acids used as respiratory substrates?
They combine with acetyl Co A and enter the Kreb cycle
333
How are proteins used as respiratory substrates?
Different amino acids can enter different stages of aerobic respiration e.g. serine can be converted into pyruvate
334
Which respiratory substrate can be converted into acetate and enter the Krebs cycle via the link reaction?
fatty acids
335
Which molecule can be deaminated and the rest of the molecule enetrs the Krebs cycle directly?
amino acids
336
Why do lipids have the highest a mean energy value per gram?
Lipids contain large chains of hydrocarbons which are a source of protons
337
What is the formula for the respiratory quotient?
CO2 produced/ O2 consumed
338
What is the RQ value for glucose?
1
339
What is the RQ value for fatty acids?
0.7
340
What is the RQ value for proteins?
0.8
341
What does an RQ value of over 1 suggest?
Anaerobic respiration is taking place
342
In an investigation into respiration, the RQ value was calculated as 0.82. Suggest which respiratory substrate was being used.
Protein
343
In an investigation into respiration, the RQ value was calculated as 0.99. Suggest which respiratory substrate was being used.
Glucose
344
In an investigation into respiration, the RQ value was calculated as 0.70. Suggest which respiratory substrate was being used.
Fatty acids
345
In an investigation into respiration, the RQ value was found to be 2.3. Suggest what can be deduced from these findings?
Anaerobic respiration has occurred
