Metabolism

Question 1

Define Metabolism

Answer 1

Sum of all chemical reactions that take place in a living organism. Essential to maintenance of life

Question 2

Name the 4 purposes of metabolism

Answer 2

Mechanical Work

Active Transport

Synthesis

Nervous Transmission

Question 3

Define Catabolism and Anabolism

Answer 3

Catabolism - break down of complex molecules to simple ones

Anabolism - synthesis/assembly of complex molecules

Question 4

Define Gibbs free energy

At equilibrium what is the value of Delta G?

Answer 4

The maximum amount of energy in a system that is available for useful work

At equilibrium Delta G = Zero

Question 5

Define Exergonic and Endergonic

Answer 5

Exergonic (Exothermic) = A spontaneous reaction has a negative delta G and releases energy

Endergonic (Endothermic) = A reaction with a positive delta G needs an input of energy to proceed

Question 6

Explain how a graph of an exergonic and endergonic reaction would looks: position of reactants and products, delta G value and axis

Answer 6

X axis: Time

Y axis: Gibbs Free Energy

Exergonic Reactions:

Reactants higher than products
Delta G is less than zero

Endergonic Reactions

Reactants are lower than products
Delta G is greater than zero

Question 7

Explain energy in terms of catabolic reactions and give examples of glycogen, triglyceride and protein

Answer 7

Catabolic reactions release energy

Glycogen to glucose + energy

Triglyceride to glycerol + fatty acid + energy

Protein to Amino acids + energy

Question 8

Explain energy in terms of anabolic reactions and give examples

Answer 8

Anabolic reactions need energy

Glucose + glucose (energy) to make glycogen

Glycerol + fatty acid (energy) to make triglycerides

Amino acid + amino acid (energy) to make protein

Question 9

Explain why reactions are coupled

Answer 9

Reactions are coupled so that the energy released from one drives another

Question 10

Name the energy currency for metabolic reactions

Answer 10

ATP

Question 11

Give the equation for hydrolysis/ condensation of ATP and what is this catalysed by

Answer 11

ATP + Water to make ADP + Pi + Energy

Reversible Reactions

Catalysed by ATPase

Question 12

Explain how all three classes of macronutrients are a source of ATP

Answer 12

Carbohydrates via glucose or glycogen broken down in the glycolytic pathway

Fats via breakdown of fatty acids

Proteins from the carbon skeletons of amino acids

Question 13

Explain how nutrients are a source of ATP

Answer 13

Energy released during the breakdown (oxidation) of nutrients is used to make ATP

When this happens directly it is called substrate phosphorylation - a small amount of ATP is made this way

Most ATP is made indirectly through the process of oxidative phosphorylation

The involve two intermediates which come from B vitamins: NAD and FAD

Question 14

Explain what happens when NAD and FAD are reduced and where this takes place

Answer 14

The passing or protons and electrons to NAD or FAD during the oxidation f macronutrients which are then passed on in the electron transport chain eventually causing the reduction of oxygen to water

NADP is also a carrier

This takes place in the electron transport chain in the mitochondria

Question 15

Explain what happens int he electron transport chain and how much ATP is yielded from NADH and FADH

Answer 15

Reducing equivalents converted to usable energy by synthesis of ATP

Oxidation of each NADH yields 2.5 ATP

Oxidation of each FADH yields 1.5 ATP

The NAD and FAD are regenerated to take part in further metabolism

The hydrogen eventually combines with oxygen to form water

Question 16

Explain the following metabolic states: fed state, post absorptive, fasting and starvation

Answer 16

Fuels utilised and stored will vary with the ‘Metabolic state; the body is in at any time

Fed State - predominantly glucose metabolism for energy and storage, fats stored, protein synthesis

Post Absorptive - Some use of stored glucose, some limited fat metabolism

Fasting - Glucose stores utilised for energy and increasing fat metabolism

Starvation - Fats from stores and some muscle protein utilised

Question 17

Name the different site of pathways within the cell

Answer 17

Mitochondria - protein synthesis

Cytoplasm - Glycolysis

Cytoplasm - Esterification of fats

Mitochondria - citric acid cycle

Mitochondria - Oxidative Phosphorylation

Mitochondria - Beta oxidation of fatty acids

Question 18

Explain what the role of enzyme is

Answer 18

Most reactions require energy to initiate them

In biological systems the problem is overcome by enzymes

Enzymes are catalyst made from globular proteins which overcome the need for a large input of energy

The vast majority of reactions in the body involve enzymes

Many enzymes require cofactors which are ions or vitamins that are associated with the enzyme