Energy Reactions In Cells

Question 1

Define metabolism

Answer 1

Metabolism is the set of processes which derive energy and raw materials from food stuffs and use them to repair, growth and activity of the tissues of the body to sustain life.
(all about the extraction and utilisation of energy)

Question 2

Where does metabolism start

Answer 2

It begins in the Gi tract as food is broken down into nutrients which is taken up into the blood.

Question 3

What is cell metabolism?

Answer 3

Small chemical changes
Many reactions but few reaction types
Reactions are organised into metabolic pathways, which are distinct but integrated. Some in all cells, some in some cells and some only in compartments within cells.

Question 4

What is the purpose of metabolic pathways?

Answer 4

Help us to picture what is going on, pathways are organised into maps showing: 
Start 
Intermediate (metabolites)
End points 
Interconnections

Question 5

What are the roles of catabolic pathways?

Answer 5

• Break down larger molecules into smaller ones (intermediary metabolites)
• Release large amounts of free energy
• Oxidative - Release H atoms and have ‘reducing power’

Question 6

What are the roles of anabolic pathways?

Answer 6

• Synthesise larger important cellular components from intermediary metabolites
• Use energy released from catabolism (ATP)
• They are reductive (i.e. they use the H released in catabolism)

Question 7

What are the products of catabolism?

Answer 7

• Building block materials (sugars, amino acids, fatty acids). These are for the dynamic state of cell components (turnover), cell growth and division, repair.
• Organic precursors (Acetyl CoA). This allows for the interconversion of building block material.
• Biosynthetic reducing power (NADH, NADPH)
• Energy for cell function (ATP)

Question 8

What is energy?

Answer 8

The capacity to do work

Question 9

What are different types of work?

Answer 9

Biosynthetic work (anabolism)- synthesis of cellular components

Transport work - membranes (for the maintenance of ion gradients and for nutrients uptake)

Specialised functions inc-
Mechanical work (muscle contraction), Electrical work (nervous impulse conduction) and Osmotic work (in the kidney).

Question 10

What is the difference between calorie and Calorie?

Answer 10

calorie = 1 calorie 
Calorie = 1000calories (1kcal) =4.2 kJ.

Question 11

What energy required for whole body?

Answer 11

Basal Metabolic Rate- energy required by an awake individual during physical, digestive and emotional rest at 18*C

Activity (Muscular work)

Specific Dynamic of food (approx 150kcal) This is the cost of ingestion, digestion and absorption of food.

Question 12

What happens if we consume more energy than need?

Answer 12

Growth -syntheis of new tissue (repair, children, pregnancy)
Production of adipose tissue

Question 13

How long survive with just water?

Answer 13

Can survive approx 20-70 days if given water. This means there must be important regulatory mechanisms to govern supply an utilisation of energy.

Question 14

Why is chemical bond energy good?

Answer 14

It can be used directly without prior conversion to heat.

Man is ISOTHERMAL. This means that they cannot use heat energy for work.

Question 15

What is an Exergonic energy change?

Answer 15

Release energy (negative gibbs).
Spontaneous
In catabolic pathways

Question 16

What is an Endergonic energy change?

Answer 16

Require energy (positive gibbs)
In anabolic pathways.

Question 17

What are Standard conditions?

Answer 17

25 degrees celsius,
1 atm
1 M
pH 7

But, cell has NON STANDARD conditions.

Question 18

What is a redox reaction?

Answer 18

This is when both oxidation and reduction at once

Question 19

What is oxidation?

Answer 19

Removal of electrons

Removal of H-atoms (H+ + e-)

Question 20

What does OIL RIG stand for?

Answer 20

Oxidation 
Is 
Loss 
Reduction 
Is 
Gain
(of electrons)

Question 21

Give some examples of H carrier molecules?

How can they be used as evidence to show a cycle is taking place?

Answer 21

NAD+ / NADH + H+
NADP+ / NADPH + H+
FAD / FADH2

Total conc of oxidised and reduced carriers is constant Therefore, must be a cycle between oxidative and reductive processes.

Question 22

How do H-carrier molecules act as carriers of reducing power?

Answer 22

ATP production -(NADH + H+)

Biosyntheiss (NADPH)

Question 23

What are the properties of H carriers?

Answer 23

Complex molecules (contain components from vitamins (B Vitamins))
Converted to reduced form by adding two H atoms (H+ +e-)
H+ dissociated into solution

Question 24

How can the energy released during oxidative metabolism be used?

Answer 24

The energy released from food by oxidation is exergonic.it can be used:

• Directly eg the use of NADPH to drive biosynthesis
• Indirectly eg In mitochondrial systems to drive ATP production (oxidative phosphorylation)

Question 25

What is the structure of ATP?

Answer 25

Adenine, Ribose and three phosphates

Question 26

How much energy lost gained when +/- a phosphate?

Answer 26

31kJ mol-1.

When you remove a phosphate, it creates it (negative)

Question 27

Is ATP a store or a currency?

Answer 27

ATP is NOT a store! It is a currency. This is because there is limited conc of ADP.

ATP is stable! This allows energy flow to be controlled.

Question 28

How much ATP is in our bodies?

Answer 28

Our body contains 250g of ATP but, turn over body weight in ATP every day.

Question 29

When are anabolic pathways activated?

Answer 29

Anabolic pathways are activated when ATP levels are high

Question 30

When are catabolic pathways activated?

Answer 30

Catabolic pathways are activated when ATP conc. is low but ADP and AMP conc are high.

Question 31

What is adenylate kinase?

Answer 31

It is a phosphotransferase enzyme that catalyzes the interconversion of adenine nucleotides (ATP, ADP, and AMP). It combines two ADP to produce an AMP and ATP.

Question 32

What are high energy signals?

Answer 32

High energy signals activate anabolic pathways. They inc.:
ATP
NADH
NADPH
FAD2H

Question 33

What are low energy signals?

Answer 33

Low energy signals activate catabolic pathways. They inc.:
ADP, AMP
NAD+
NADP+
FAD

Question 34

How is energy stored in cells?

Answer 34

In form of polymer macromolecules of fuel molecules eg glycogen, trigyceride.

Question 35

How is some energy stored in muscles?

Answer 35

Creatine phosphate. This is used as a reserve of high energy stores that can be used immediately.

Question 36

How does creatine phosphate work?

Answer 36

Creatine +ATP (using creatine kinase as enzyme) = Phosphocreatine (PCr) + ADP.

When ATP high, creatine phosphate is formed, `If ATP conc falls, reaction reverses and produces a short term burst of ATP.

Question 37

What is creatine kinase a marker of?

Answer 37

Creatine Kinase is a marker of myocardial infarction.
CK is released from cardiomyocytes. when they are damaged by cardiomyocytes. This appears in the blood after a few hours and it is how we diagnose an MI.

Look at isoform distribution (70:30), so know its form the heart.

Question 38

How is creatine a clinical marker?

Answer 38

Related to muscle mass as constant degradation. Can be used to measure muscle mass in the body because the amount of creatinine is proportional to muscle mass.

Can also look at creatinine conc in the Urine as a marker of urine dilution. This is because the release of creatine is constant and level all day. It can be used to estimate true urinary loss of many substances.