Metabolism

Question 1

What is Metabolism?

Answer 1

Metabolism is the sum of all biochemical reactions taking place in the cell (the sum of all anabolic and catabolic reactions)

Question 2

Describe catabolism and its characteristics

Answer 2

Catabolism is the process by which large molecules are decomposed into smaller molecules. -It is degradative and oxidative -It liberates energy stored in the bonds of large molecules -Converging

Question 3

Why is catabolism converging?

Answer 3

Because a great variety of different compounds re used to produce the same products.

Question 4

Describe anabolism and its characteristics

Answer 4

Anabolism is a process by which large and complex molecules are built up from smaller components. -Biosynthetic and reductive -Energy is required to create bonds -Diverging

Question 5

What are the three ways to describe oxidation?

Answer 5

1) Oxidation is joining with an Oxygen 2) Oxidation is losing an hydrogen 3) Oxidation is losing an electron

Question 6

What is reduction?

Answer 6

Reduction is gain of electrons.

Question 7

What is redox potential?

Answer 7

Reduction potential is a mesure of how readily a compound donates and electron compare do Hydrogen.

Question 8

If reduction potential is less than zero (is negative)…

Answer 8

It means that the reduced form of the compound has lower affinity for electrons than hydrogen.

Question 9

What are the two conditions for a spontaneous redox reaction to occur?

Answer 9

-Reduction potential has to be positive and ΔG has to be negative.

Question 10

What are the two conditions for a non spontaneous reaction to (not) occur?

Answer 10

-Reduction potential has to be negative and ΔG has to be positive.

Question 11

How is energy provided in cells?

Answer 11

It is provided through high energy electrons.

Question 12

What are high energy electrons?

Answer 12

Electrons with negative redox potential that tend to flow to positive redox potential.

Question 13

Describe photoautotrophs

Answer 13

The energy source of photoautotroph is the sun and the carbon source is CO2.

Question 14

Describe photoheterotrophs

Answer 14

The energy source for photoheterotroph is the sun and the carbon source are organic compoounds.

Question 15

Describe chemoautotrophs

Answer 15

The energy source of chemoautotrophs are chemical bonds and the carbon source is CO2

Question 16

Describe chemoheterotrophs

Answer 16

The energy source of chemoheterotrophs are chemical bonds and the carbon source are organic compounds.

Question 17

Describe phototrophs in general

Answer 17

Phototrophs capture energy from the sun and use it to oxidise H2O or H2S to release high energy electrons.

Question 18

Describe chemotrophs in general:

Answer 18

Chemotrophs oxidise organic compounds to release high energy electrons.

Question 19

What are electron carriers?

Answer 19

Are intermediate of redox reaction in the metabolic pathways of the cell.

Question 20

Why do NADH and FADH2 need to be re-oxidised?

Answer 20

Because they’re present in small amount to is important to recycled them in order to keep the metabolism in function.

Question 21

What are final electron acceptors?

Answer 21

The final product of a metabolic pathway that allows the regeneration of electron carriers.

Question 22

Describe the first stage of metabolism

Answer 22

In the first stage of metabolism macromolecules are degraded to their monomeric units. It occurs outside the cell n the process of digestion.

Question 23

Describe the second stage of metabolism:

Answer 23

In the second stage of metabolism, the small molecules produced in the previous stage enter the cell and are converted into a small number of simple molecules. The products of this stager are: 2-Carbon Acetyl CoA and some ATP.

Question 24

Describe the third stage of metabolism:

Answer 24

The acetyle group of Acetyl CoA enter the Kreb’s cycle where it is completely oxidise to CO2 and H2O.

Question 25

What are the two ways to phosphorylate ATP?

Answer 25

Substrate level phosphorylation and oxidative phosphorylation

Question 26

Describe substrate level phosphorylation

Answer 26

Energy for phosphorylation is obtianed from substrate of biochemical reaction and a phosphate group is directly transfered to ADP to form ATP.

Question 27

Describe oxidative phosphorylation

Answer 27

High energy electrons are used to reduce O2 and H2O and this energy is used to create an electrochemical gradient across the membrane that then generates the energy required to synthesise ATP.

Question 28

Describe the outer membrane of mitochondria

Answer 28

The outer membrane is permeable to most molecules and this is why the intermembrane space has similar characteristics to the cytoplasm.

Question 29

Describe the inner membrane of mitochondria

Answer 29

The inner membrane is impermeable to most molecules and contain proteins for the electron transport chain

Question 30

What are the two stages of the chemiosmotic process?

Answer 30

Electron transport and ATP synthesis *Oxidative phosphorylation).

Question 31

Describe the electron transport

Answer 31

Electron from NADH enter complex I while electrons from FADH2 enter complex II. Electrons are then handed down from higher to lower redox potentials and finally they are transfere to O2 to form H2O.

Question 32

What are the two gradients formed as a result of electron transport?

Answer 32

1) Chemiosmotic gradient 2) Electrical Gradient

Question 33

Describe the chemiosmotic gradient

Answer 33

The concentration of protons is higher in the intermembrane region thus protons would flow back into the matrix but the lipid bilayer is impermeable to them. pH is lower in the intermembrane region.

Question 34

Describe the electrical gradient:

Answer 34

A difference in charge across the membrane resulting from the unbalanced presence of protons (intermembrane space is more positively charged than the matrix).

Question 35

How is energy stored in the chemiosmotic gradient used to synthesize ATP?

Answer 35

Protons flow back through ATP synthase causing the rotor to turn and such a conformation change lead to ATP synthesis.

Question 36

What effect has 2,4-Dinitrophenol on the production of ATP?

Answer 36

It forms a proton channel in the inner membrane of the mitochondrion so that the proton gradient cannot be formed and energy is release as heat instead of ATP.

Question 37

Describe the two subunits of ATP synthase

Answer 37

F1 subunit protrudes into the mitochondrial matrix while F0 subunit is hydrophobic and remain in the inner membrane (it contains the proton channel).