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WJEC A Levels > Biology Unit 3 > Flashcards

Biology Unit 3 Flashcards

(53 cards)

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1
Q

Where does the light dependent reaction of photosynthesis take place

A

On the thylakoid membrane

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2
Q

Where does the light independent reaction of photosynthesis take place

A

In the stroma

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3
Q

What is the colour of chlorophyll a

A

Blue/green

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4
Q

What is the colour of chlorophyll b

A

Yellow/green

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5
Q

What is the compensation point of respiration and photosynthesis

A

The maximum point up to which respiration can provide the CO2 needed by photosynthesis until the rates of these reactions are the same.

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6
Q

Define ‘limiting factor’

A

Something which directly affects the rate of a process if its quantity is changed.

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7
Q

Where does photosynthesis occur in the leaves

A

In the palisade tissue

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8
Q

What does an absorption spectrum show

A

The absorption of light by different pigments

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9
Q

What does an action spectrum show

A

The rate of photosynthesis at different wavelengths

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10
Q

Describe the stages of the Calvin cycle

A

Ribulose bisphosphate (5C) + CO2 (catalysed by RuBisCO) forms an unstable 6C compound.
This splits into 2x glycerate-3-phosphate (GP).
Using 1 ATP and 1 red. NADP GP is converted to 2x triose phosphate (TP).
1/6 of TP created is used to make hexose sugar (glucose).
5/6 of TP forms ribulose phosphate (5C) in intermediate reactions, then using ATP ribulose bisphosphate is generated and the cycle begins again

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11
Q

Where does glycolysis take place

A

Cytosol/ cytoplasm of the cell

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12
Q

Where do fats enter the respiratory pathway

A

Broken down into glycerol and fatty acids
Glycerol (3C) is converted into triose phosphate.
Long, fatty acid chains molecules are split into 2C fragments which enter the Krebs cycle as acetyl co-enzyme A.

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13
Q

What occurs in the link reaction of respiration

A

Pyruvate is converted to acetyl co-A by the addition of co-A, elimination of CO2 and the reduction of NAD

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14
Q

Describe anaerobic respiration in animals

A

Glucose is converted to pyruvate generating 1 ATP and reducing 1 NAD which is then converted to lactate using the hydrogen from the reduced NAD (NAD is regenerated) (this occurs twice per molecule of glucose)

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15
Q

Describe anaerobic respiration in plants

A

Glucose is converted to pyruvate generating 1 ATP and reducing 1 NAD which is then converted to ethanal (eliminates 1 CO2) and then to ethanol using the hydrogen from the reduced NAD (NAD is regenerated) (this occurs twice per molecule of glucose)

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16
Q

What is the oxygen debt in respiration

A

The amount of oxygen needed to remove the lactic acid that built up during anaerobic respiration

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17
Q

What is the yield of ATP under anaerobic conditions

A

2 ATP per molecule of glucose

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18
Q

State the two differences between Gram positive and Gram negative bacteria

A

Gram negative bacteria have an additional outer lipopolysaccharide layer that Gram positive do not.
Gram positive bacteria have a thicker peptidoglycan/murein cell wall compared to Gram negative.

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19
Q

Name the two categories of antibiotic

A

Bacteriostatic: prevents bacteria reproducing
Bactericidal: kills the bacteria

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20
Q

How does penicillin work as an antibiotic

A

Prevents the bonds that link the peptidoglycan molecules from forming during reproduction of the bacteria. The walls weaken, water enters by osmosis and the cell can burst.

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21
Q

How does lysozyme kill bacteria

A

Hydrolyses the glycosidic bonds holding the peptidoglycan molecules. This weakens the cell wall, water enters by osmosis and the cell can burst.

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22
Q

What equipment is used to create a total count of bacteria

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A

A haemocytometer

23
Q

What does ‘niche’ mean in ecology

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A

The role of an organism in an ecosystem, generally a feeding role.

24
Q

Define deflected succession

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A

Where a subclimax community is maintained usually by human interference e.g mowing lawns and school fields.

25
Define detritivores and their role in decomposition
Animals with a tube gut that feed on dead organic materials e.g woodlice and earthworms. In the process of consuming their food they help to speed up decomposition by increasing the surface area of the dead organic material for the action of saprophytes.
26
Define saprophytes and their role in decomposition
Fungi and bacteria the carry out extracellular digestion of the organic material to obtain nutrients. They decompose the dead material.
27
How is ammonium converted to nitrate in the nitrogen cycle
Nitrosomonas converts ammonium to nitrite and Nitrobacter converts nitrite to nitrate.
28
How is nitrogen gas converted to ammonium
Nitrogen fixing bacteria that are either free living in soil like Azotobacter or living in a mutualistic relationship with legumes and living in the root nodules like Rhizobium
29
How is nitrate converted to nitrogen gas
Denitrifying bacteria, such as Pseudomonas. These bacteria use nitrate to provide oxygen for respiration (as denitrification occurs in otherwise anaerobic conditions), the nitrogen atoms remaining are converted into nitrogen gas.
30
State the seral stages of primary succession
Pioneer species (lichens) ➔mosses ➔ grasses ➔ herbaceous plants ➔ shrubs ➔ climax community (trees).
31
What is occurring in bacteria or animal populations during the lag phase of population growth
Bacteria: replicating DNA, synthesising enzymes Animals: reaching sexual maturity
32
How is coppicing an example of a sustainable management strategy
Coppicing is where woodland is divided into different areas to be cut down in rotation. Trees are cut to the stumps and the wood re-grows from the stump. The trees produce long straight stems which can be harvested.
33
Name the 9 planetary boundaries
Ozone depletion Biosphere integrity Freshwater consumption Land system change Ocean acidification Aerosol loading Biochemical flows Chemical pollution Climate change
34
Which planetary boundaries have we crossed
Climate change Biochemical flows Land system change Biosphere integrity
35
Where is ATP synthetase located in chloroplasts and mitochondria
Within the stalked particles of the inner membranes: Thylakoid membrane in chloroplasts. Crista in mitochondria.
36
Characteristics of simple nerve nets e.g Hydra
Unmyelinated neurones - slow response Small number of effectors Can only respond to a limited number of stimuli
37
Negative feedback loop of the nervous system
Stimulus -> receptor -> sensory neurone -> relay neurone in CNS -> motor neurone -> effector -> response
38
What is the advantage to an organism having myelinated neurones
Action potentials only generated as nodes of Ranvier so they have to 'jump' to each node (saltatory conduction) reducing speed of transmission and also the amount of ATP required
39
What is the advantage to an organism having a wider axon diameter
More sodium ions can flow through the axon so faster speed of transmission
40
What do synapses ensure
Uni-directional transmission because neurotransmitter is released on one side and its receptors are on the other
41
Acetylcholine example
Acetylcholine is hydrolysed by acetylcholinesterase into choline and ethanoic acid. Acetyl CoA and choline can combine to regenerate acetylcholine and CoA
42
What does the sodium-potassium pump do
Actively transports 3 sodium ions out and 2 potassium ions into the axon when the sodium channels are closed to maintain resting potential and make the membrane polarised
43
Where is the sensory neurone cell body found in the CNS
In the dorsal root ganglion
44
Nervous system classifications
Central -> brain and spinal cord Peripheral -> cranial and spinal nerves and their roots and branches
45
During ultrafiltration what do the small molecules pass through
Capillary pores in the endothelial cells The basement membrane of the capillary (a layer of proteins and glycoproteins that acts like a molecular sieve) Filtration slits made by podocytes which interdigitate around the capillary
46
How is high filtration pressure created in the glomerulus
The difference in diameter between the wider afferent arteriole and the thinner efferent arteriole entering and leaving the glomerulus High blood pressure in the renal artery
47
How is the proximal convoluted tubule adapted for reabsorption
- Cuboidal epithelial cells have microvilli for larger surface area - Basal channels increase the concentration gradient - Tight junctions prevent molecules from diffusing back into the glomerular filtrate - Many mitochondria for ATP for active processes
48
What occurs in the loop of Henle
The Counter Current multiplier mechanism which enables a maximum concentration to be built up at the apex of the loop
49
How is the absorption of water regulated in the collecting duct
By the hormone ADH, if ADH is released from the pituitary gland it causes aquaporins to be incorporated into the collecting duct membrane which means that more water can flow out of the tubule and be absorbed by the blood, urine output is low
50
Why do animals that need to conserve water have longer loops of Henle
A greater solute concentration is created in the medulla as there is more opportunity to pump ions into the medulla. As a result more water is reabsorbed and more concentrated urine is produced.
51
Outline haemodialysis
Blood is passed through an artificial kidney machine The blood and dialysis fluid are separated by a partially permeable membrane and have a counter current flow to maintain steep diffusion gradients
52
Outline peritoneal dialysis
The peritoneum (membrane that lines the abdomen cavity) is filled with dialysis fluid and acts as the filter Fluid is then drained off This needs to be done several times a day because there is no counter current flow and so the dialysis fluid reaches the same concentration as the blood
53
Where is the proton concentration gradient located in mitochondria
Protons are pumped out of the matrix, across the inner membrane and into the intermembrane space. Low proton concentration in the matrix, high proton concentration in the intermembrane space

WJEC A Levels (10 decks)

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