Topic 5 - Energy transfers in and between organisms

Question 1

Describe what happens during photoionisation in the LDR

Answer 1

Chlorophyll absorbs light
Electrons are lost

Question 2

Explain why the student marked the origin in pencil rather than ink

Answer 2

Ink and leaf pigments mix

Question 3

Describe the method the student used to separate the pigments after the solution of pigments had been applied to the origin

Answer 3

Level of solvent below origin/line
Remove before (solvent) reaches the top/end

Question 4

Heat stress leads to a decrease in the LDR. Explain why this leads to a decrease in the LIR

Answer 4

Less ATP
Less NADPH/reduced NADP

Question 5

How does a decrease in rubisco lead to a decrease in photosynthesis

Answer 5

Less/no CO2 (reacts) with RuBP

Question 6

Where is rubisco found

Answer 6

In the stroma of the chloroplast

Question 7

Explain how chemicals which inhibit the decolourisation of DCPIP could slow the growth of weeds

Answer 7

Less/no ATP produced
Less/no NADPH produced
Less/no GP converted/reduced to TP

Question 8

Most of the light falling in ecosystems is not used in photosynthesis. Explain why

Answer 8

Light is the wrong wavelength
Light is reflected
Light misses the chlorophyll/chloroplasts
CO2 conc/temp is a limiting factor

Question 9

Name 2 products of the LDR that are used in the LIR

Answer 9

ATP
NADPH

Question 10

Atrazine binds to proteins in the electron transfer chain in the chloroplasts of weeds, reducing the transfer of electrons down the chain. Explain how this reduces the rate of photosynthesis in weeds

Answer 10

Reduced transfer of protons across the thylakoid membrane
Less ATP produced
Less NADPH produced
So LIR slows/stops

Question 11

State 2 roles of nitrogen in living organisms

Answer 11

Building proteins
Building nucleic acids

Question 12

Describe the process of ammonification

Answer 12

The conversion of nitrogen- containing molecules in dead organisms/waste into ammonia/ammonium compounds/ammonium ions
By bacteria/saprobionts/soil in microorganisms

Question 13

Suggest how flooding might impact the availability of nitrates in the soil

Answer 13

Nitrates would be lost/removed from the soil OR
Nitrate availability in the soil would be reduced

Question 14

Describe the role of microorganisms in the phosphorus cycle

Answer 14

Function as decomposers/saprobionts
That break down the molecules in dead organisms/waste matter to release phosphate ions

Question 15

State a role of phosphorus in living organisms

Answer 15

Building phospholipids
Building nucleic acids/DNA/RNA
Building ATP

Question 16

Define the term saprobionts

Answer 16

Bacteria/fungi
Organisms that gain their nutrition from dead matter/organic waste
Carry out extracellular digestion/secrete enzyme onto their food

Question 17

Explain why decomposers are an essential part of any ecosystem

Answer 17

They release nutrients (from dead or waste material) making them available again to other organisms

Question 18

Describe how acetyl co-enzyme A is formed in the link reaction

Answer 18

Oxidation of/ hydrogen removal from pyruvate and co2 released
Addition of co-enzyme A

Question 19

In muscles pyruvate is converted to lactate during anaerobic respiration. Explain why converting pyruvate to lactate allows the continued production of ATP during anaerobic respiration

Answer 19

Regenerates/produces NAD
(NAD used) in glycolysis

Question 20

In muscles some of the lactate is converted back to pyruvate when they are supplied with oxygen

Answer 20

Lactate/lactic is toxic, harmful, causes muscle fatigue, cramp
Pyruvate is used in anaerobic respiration

Question 21

Respiration produces more ATP per molecule of glucose in the presence of oxygen than it does when oxygen is absent. Explain why

Answer 21

Oxygen is the final/terminal acceptor
No Krebs cycle/ No link reaction

Question 22

Explain why an increase in biomass in plants over a long period is always less than the total mass of hexose sugars produced in plants given the same time period

Answer 22

1. Some CO2 in respiration is released
2. Some hexose used up in respiration
3. Some parts of plant eaten by consumers/leaf fall and decomposition

Question 23

One of the products produces from TP is hexose sugars. Give 2 uses for hexose sugars inside plant cells

Answer 23

Conversion into starch for storage
Conversion into sucrose for transport around the plant
Conversion into cellulose for cell walls
Respiration to produce ATP

Question 24

Name one other product that is made during the Calvin cycle and state its role inside of plant cells

Answer 24

Amino acids
Which are used for protein synthesis
OR

Lipids/glycerol/fatty acids
Which can be used to build cell membranes/the waxy cuticle
OR

ADP/NADP
Can enter back into the light dependent reactions