Metabolism, Cell Respiration & Photosynthesis

Question 1

what are the two types of metabolic pathways

Answer 1

cycles (Krebs Cycle) + chain reactions (glycolysis)

Question 2

What is the importance of enzymes in the rate of reactions

Answer 2

enzymes lower the activation energy and thus increases the rate of chemical reactions

Question 3

Activation energy definition

Answer 3

the minimum amount of energy needed for a chemical reaction to occur

Question 4

What are the different types of inhibitors

Answer 4

competitive & non-competitive

Question 5

What are competitive Inhibitors

Answer 5

• they have a similar shape to the substrates
• they bind to the active site of the enzyme
• thus the substrate cannot bind to the enzyme

Question 6

What is an inhibitor

Answer 6

a molecule that binds to an enzyme and slows down or stops the enzyme’s function

Question 7

What are non-competitive inhibitors

Answer 7

• They bind to the enzyme at an alternative site, which alters the shape of the active site
• It prevents the substrate from binding to the active site

Question 8

Can the problem of competitive inhibitors be solved and how?

Answer 8

Increasing the concentration of substrates, thereby out-competing the inhibitor

Question 9

Can the problem of non-competitive inhibitors be solved and how?

Answer 9

Since the inhibitor binds to a site other than the active site, increasing the concentration of the substrate will not speed up the reaction or reduce the effect of the inhibitor

Question 10

What is end-product inhibition

Answer 10

As the enzyme converts substrate to an end-product, the process is itself slowed down as the end-product of the reaction chain binds to an allosteric site on the original enzyme, changing the shape of the active site and preventing the formation of further enzyme-substrate complexes.

Question 11

What is the purpose of end-product inhibition

Answer 11

It prevents the cell from wasting chemical resources and energy by making more of a substance than it needs

Question 12

Draw and explain the graph for a normal enzyme

Answer 12

Increasing the concentration of substrates will increase the rate of reaction until the max rate of reaction is reached and the line plateaus as all the enzymes are saturated with substrates

Question 13

Draw and explain the graph for a competitive inhibitor

Answer 13

The competitive inhibitor competes with the substrate for the active, so when the substrate concentration exceeds the competitive inhibitor max rate of reaction is reached

Question 14

Draw and explain the graph for a non-competitive inhibitor

Answer 14

the maximum rate of reaction will not be achieved regardless of substrate concentration. This inhibition lowers the number of available enzymes

Question 15

What is oxidation

Answer 15

gain of oxygen, loss of hydrogen and loss of electrons

Question 16

What is reduction

Answer 16

loss of oxygen, gain of hydrogen and gain of electrons

Question 17

What are the stages of cellular respiration

Answer 17

1) glycolysis (cytoplasm)
2) link reaction (matrix)
3) Krebs Cycle (matrix)
4) electron transport chain (inner membrane)
5) oxidative phosphorylation + chemiosmosis (inner membrane)

Question 18

Glycolysis pt.1

Answer 18

Phosphorylation: the phosphate groups from the 2 ATPs are added onto the glucose to form a less stable sugar called hexose phosphate

Question 19

Glycolysis pt.2

Answer 19

Lysis: The less 6-carbon sugar will be split into two 3-carbon sugars (triose phosphate).
The splitting process is known as lysis.

Question 20

Glycolysis pt.3

Answer 20

ATP formation: Each triosephosphate is oxidised (H atoms are removed), to form NAD+ which becomes NADH. Phosphate molecules are added to ADP to produce ATP. The end result is the formation of 2 ATP molecules, 2 NADH and 2 pyruvate molecules

Question 21

Link Reaction

Answer 21

Pyruvate is decarboxylated (decarboxylation is the removal of the C atom). The removed C atom is oxidised and produces CO2 and forms an acetyl group, thereby reducing NAD to NADH. The acetyl group combines with the coenzyme A (CoA) to form acetyl-CoA.

Question 22

Krebs Cycle pt.1

Answer 22

Acetyl CoA combines with 4-carbon compound oxaloacetate to form a 6-carbon compound.
Citrate is oxidised and NAD+ is reduced to NADH and it is also decarboxylated and releases CO2.

Question 23

Krebs Cycle pt.2

Answer 23

The 5-carbon compound is oxidised and decarboxylated to form a 4-carbon compound. CO2 and NADH is produced again.

Question 24

Krebs Cycle pt.3

Answer 24

ADP combines with phosphate group to form ATP. FAD is then reduced and forms FADH2 and NAD+ is reduced to form NADH. The cycle begins again.
Products: 2CO2, ATP, 3NADH, FADH2 (1 pyruvate)

Question 25

Electron transport chain pt.1

Answer 25

1) NADH supplies 2 electrons to the first carrier in the chain (reforming NAD+). These electrons move along the chain of electron carriers giving up energy each time they pass from one carrier to the next.

2) FADH2 is also oxidized (forms FAD+) and releases its electrons a little later into the electron transport chain.

3) Energy is released as the electrons are passed along the carrier proteins.

Question 26

Electron transport chain pt.2

Answer 26

4) This energy is used to pump H+ ions across the inner mitochondrial membrane from the matrix to the inter-membrane space.

5) This accumulation of H+ ions in the inter-membrane space creates an H+ concentration gradient between the matrix (less concentrated) and the inter-membrane space (more concentrated)

6) Protons (H+) flow back from the inter-membrane space to the matrix through special protein channels located in the inner mitochondrial membrane called ATP synthase

Question 27

Electron transport chain pt.3

Answer 27

7) As the protons pass across the membrane, they release energy, which is used by the ATP synthase to produce ATP through a phosphorylation reaction.

8) This process is called oxidative phosphorylation because oxygen is the final electron acceptor and the energy released by reducing oxygen to water is used to phosphorylate ADP and generate ATP.

9) For each glucose molecule, about 32 molecules of ATP are produced.

Question 28

What is chemiosmosis

Answer 28

Chemiosmosis is the process in which energy from a proton gradient is used to make ATP

Question 29

The importance fo oxygen in aerobic respiration

Answer 29

Oxygen is reduced by the electrons forming water. If oxygen is not present to accept electrons: reduced NAD and reduced FAD will not be oxidised to generate NAD+ and FAD so there will be no further hydrogen transport. The electron transport chain will stop and ATP will no longer be produced by chemiosmosis. Without enough ATP, cells can’t carry out the reactions they need to function.

Question 30

Structure of mitochondrion

Answer 30

Matrix, inner membrane, outer membrane, cristae, ribosomes & DNA, inter membrane space

Question 31

Properties of the intermembrane space

Answer 31

• low pH due to high concentration of H+
• the concentration gradient is formed due to oxidative phosphorylation
• it is essential for ATP synthesis

Question 32

Properties of inner membrane

Answer 32

• site of electron transport chain
• site of ATP synthase

Question 33

Properties of cristae

Answer 33

They have a large surface area as they are folded and they are located in the inner membrane

Question 34

Properties of outer membrane

Answer 34

Impermeable to H+

Question 35

Where does photosynthesis occur

Answer 35

Light-dependent: thylakoid membranes and inter membrane space
Light-independent: stroma