IB Biology HL C Interaction and Interdependence Topic Practice

a. used as a source/(temporary) store of energy / is the energy currency of the cell;

b. releases energy when converted to ADP/when a phosphate is removed;

c. amount of energy released can be used/sufficient for (many metabolic) tasks;

d. active transport/another valid example;

e. ATP to ADP conversion is reversible / ATP can be regenerated from ADP;

f. can be produced in different ways/using energy from different sources/by aerobic or anaerobic respiration;

g. stable within cell so does not release energy prematurely/before needed;

h. small molecule/soluble so can move easily/quickly (through the cell);

i. cannot diffuse through membranes so is not lost from cell/to the environment;

h. The idea of ATP being small/soluble
must be there along with its
moveability.

3

Marking guidance:

max

a. ATP produced by photosynthesis/in chloroplasts

OR

photosynthesis occurs in the chloroplast / photosynthesis produces glucose;

b. ATP synthase/electron carriers/proton pumps/photosystems/pigments in the thylakoid membrane

OR

ATP synthase/electron carriers/proton pumps the inner mitochondrial membrane/cristae;

c. chlorophyll/pigments absorb light;

d. in photosystems/Photosystem I/Photosystem II/antenna complexes;

e. electrons (in chlorophyll/pigments) raised to higher energy levels/become excited;

f. (excited) electrons passed between carriers/along the electron transport chain;

g. energy from electrons used (by carriers) to pump protons $/ \mathrm{H}^{+}$ions;

h. from the stroma to the thylakoid space;

i. proton gradient generated/high concentration of protons generated in the thylakoid space/lumen;

j. protons flow back (to stroma) through ATP synthase;

k. ADP phosphorylated / ADP and phosphate converted to ATP / ATP made by phosphorylating ADP;

I. cyclic (photophosphorylation) only uses PS1 but non-cyclic uses both/PS1 and PS2;
m. water is split (by photolysis) to replace electrons lost (by photosystem);

7

Marking guidance:

max

Similarities

a. (all heterotrophs) use foods/carbon compounds/other organisms as their energy source/to use for ATP production;

b. (all heterotrophs) get energy/carbon compounds/organic compounds/glucose/carbohydrate/lipids/fats from other organisms;

Differences

c. saprotrophs/decomposers feed on dead organic matter;

d. saprotrophs/decomposers secrete digestive enzymes into the food source / digest externally;

e. consumers feed on living organisms/other organisms;

f. primary consumers feed on plants/other example of feeding relationships in a food chain;

g. detritivores ingest detritus/OWTTE;

h. digestion of food so compounds can be absorbed;

i. internal digestion in holozoic animals/detritivores;

j. energy from carbon compounds used to produce ATP by cell respiration;

5

Marking guidance:

max

a. plants/producers/autotrophs convert light to chemical energy by photosynthesis
b. chlorophyll/photosynthetic pigments absorb light
c. electrons are excited/raised to higher energy level
d. excited electrons pass along chain of electron carriers
e. energy from electrons used to pump protons across thylakoid membrane/into thylakoid space
f. chemiosmosis/proton gradient used to make ATP
g. ATP synthase generates ATP
h. pigments arranged in photosystems
i. electrons from Photosystem II flow via the electron chain to Photosystem I
j. electrons from Photosystem I are used to reduce NADP
k. ATP and reduced NADP used in the light independent reactions/Calvin cycle
I. carbohydrate/glucose/carbon compounds produced containing energy

a. producers/plants/autotrophs obtain energy from light/sun/inorganic sources

b. food contains energy / energy passed in the form of food/carbon compounds (along food chains/between trophic levels)

c. consumers obtain energy from other organisms/from previous trophic level

d. energy released (in organisms) by (cell) respiration

e. ATP produced

f. energy/ATP used for biosynthesis/movement/active transport/other valid use of ATP

g. less energy available / energy lost at each trophic level

This mark point distinguishes consumers from producers.

a. signalling chemicals/ligands bind to receptors;

b. reference to specificity / the shape (and chemical properties) of the ligand-binding site match those of the ligand;

c. receptors can be in (either) the plasma membrane / intracellular / in the cytoplasm / or nucleus

OR

ligand can bind to transmembrane receptors/receptors in the plasma membrane or intracellular receptors;

d. only cells with a receptor to a signalling chemical will respond;

e. reference to signal transduction (initiated by signalling chemical-receptor binding);

f. example of signalling chemical;

Marking guidance:

Do not accept the role of glycoproteins in cell-cell recognition or ABO glycoproteins.

For b: do not accept "complementary" as this is part of the stem question.

For e. OWTTE

For e. the reference may include the pathway followed by a given example of a signalling chemical.

Appropriate example for (f):

- Neurotransmitters/named neurotransmitter

- any named hormone

- Cytokine

- Calcium ions

4
max

a. enzymes are globular proteins with an active site (for catalysis);

b. substrates must bind to the active site to be catalysed;

c. description of induced fit mechanism / substrate can cause active site to change shape;

d. conformational changes/changes in tertiary structure do not allow substrate to bind to active site / enzyme is denatured;

e. denaturation decreases enzyme activity / enzymes no longer work;

f. high temperatures/temperatures above the optimum break bonds in the enzymes / cause conformational changes to active site / denature enzymes;

g. below the optimum temperature enzymes may be inhibited OR increased temperature increases kinetic energy, increasing enzyme activity (because of more collisions) up to optimum temperature;

h. (changes in) pH cause changes in charges /alteration of (ionic/ H) bonds (between amino acids) / affect shape of active site / the enzyme becomes denatured (at higher or lower pH values than the optimum)

i. non-competitive inhibitors bind to an allosteric site;

j. (non-competitive inhibitors) cause disruption of hydrogen/ionic/disulfide/hydrophobic interactions;

Marking guidance:

Ignore references to substrate concentration

Ignore references to competitive inhibitors

For h. do not accept that the enzyme is inhibited because of pH different from optimum.

7
max

9b continued...

9.

b

k. (non-competitive inhibitors) cause conformational change of the enzyme / changes in the active site of the enzyme;

I. (non-competitive inhibitors) decrease rate of enzyme-substrate complex formation / substrate can no longer bind to the active site / decrease enzyme activity;