Metabolism

Question 1

Define Metabolism

Answer 1

The set of processes which DERIVE ENERGY and raw MATERIALS from food and use them to support REPAIR, GROWTH and ACTIVITY of the tissues to sustain life

Question 2

What are the domains in the overview of metabolism

Answer 2

The GI TRACT where nutrients are absorbed from and lost in faeces.

The BLOOD where nutrients are transported and WASTE PRODUCTS from UTILISATION are lost (kidneys and lungs).

The TISSUES where nutrients are INTERCONVERTED for STORAGE or UTILISATION (also via SYNTHESIS). UTILISATION produces ENERGY and WASTE PRODUCTS

Question 3

How are metabolic pathways organised within tissues

Answer 3

Some occur in ALL CELLS

Some a restricted to SOME CELLS

Some may be further restricted to COMPARTMENTS within cells

Question 4

Metabolic maps show what?

Answer 4

they show start and end points as well as intermediates/metabolites also interconnections

Question 5

Name the two main metabolic pathways and outline their functions

Answer 5

CATABOLIC- BREAKDOWN of larger molecules to smaller molecules releasing large amounts of FREE ENERGY and are usually OXIDATIVE (releasing protons and electrons).

ANABOLIC- SYNTHESIS of larger important cellular components from intermediary metabolites USING ENERGY via usually REDUCTIVE pathways

Question 6

What are fuel molecules metabolised to supply

Answer 6

‘Building blocks’- i.e sugars, amino or fatty acids. A dynamic state of cell components, cell growth, division and repair

Organic precursors- i.e Acetyl CoA for interconversion

Biosynthetic reducing power (NADH NADPH)

Energy for cell function (ATP)

Question 7

What is energy and what is it used for

Answer 7

The capacity to do work

BIOSYNTHETIC (anabolism)
TRANSPORT (membranes- nutrient uptake and ion gradients)
SPECIALISED (mechanical eg contraction, electrical eg nervous, osmotic eg kidneys)

Question 8

True or False, in a normal healthy adult the average daily energy intake is equal to the average daily expenditure?

Answer 8

True, food in is equal to work and heat out roughly

Question 9

What is the standard unit of energy and what is it per gram for fat, carbs, protein and alcohol in Kcal (1 calorie is 4.2 SI Units)

Answer 9

SI UNIT of energy is the Joule (J). Dividing by 4.2 gives calories

Fat is 9 kcal, carb is 4 kcal, protein is 4 kcal, alcohol is 7 kcal.

Question 10

What is the base metabolic rate for a 70KG male and a 58KG woman per day at 18C?

Answer 10

1700kcal for men and 1400kcal for women

Question 11

How many calories are expended through activity (muscular work) roughly per day

Answer 11

1000 to 300 kcal through skeletal and cardiac muscle

Question 12

How much energy is used per day to ingest, digest and absorb food?

Answer 12

150kcal

Question 13

Excess energy is stored when intake exceeds energy required. What is it used for and what if it is less than the energy required?

Answer 13

Growth occurs (new tissue, repair, children, pregnancy) or production of adipose tissue.

TISSUE LOSS occurs if intake < energy required
Can survive 20-70 days with water

Question 14

List one types of energy and which is most predominantly used in the body.

Answer 14

Heat, light, mechanical, electrical, osmotic. CHEMICAL BOND ENERGY most used form.

Question 15

What does the term isothermal mean and how does it apply to man?

Answer 15

Heat energy is not used to drive reactions in man

Question 16

What are the two energy changes associated with chemical reactions and how do they relate to Gibbs free energy?

Answer 16

Exergonic- release energy with a NEGATIVE Delta G
Reaction is ‘spontaneous/feasible’

Endergonic- require energy with a POSITIVE Delta G
Reaction is not ‘spontaneous/feasible’ and requires energy input

Question 17

True or false, the value of delta G indicates whether a reaction is spontaneous and indicates the rate?

Answer 17

False, it only indicates its spontaneity

Question 18

What is a redox reaction. Explain redox in terms of electrons and hydrogen.

Answer 18

A reaction where a species is oxidised and another is reduced.

OIL RIG- Ox is loss, Red is gain

Question 19

Name three major carrier molecules in the oxidised and reduced forms.

Answer 19

Nicotinamide adenine dinucleotide (NAD, NADH + H+)

Nicotinamide adenine dinucleotide phosphate (NADP+, NADPH +H+)

Flavin adenine dinucleotide (FAD, FADH2)

Question 20

True or false, the concentration of oxidised or reduced carries is constant, cyclical, and they act as carriers of reducing power.

Answer 20

True, the concentrations are constant and must be cycled to maintain this. They act as carriers of reducing powers for ATP production and biosynthesis (NADH and NADPH)

Question 21

Briefly outline H carrier molecules

Answer 21

Complex molecules with components from vitamins (B vitamins) that are converted to reduced form by adding two H atoms (proton and electron). The proton dissociates into solution.

Question 22

How can energy released during oxidative metabolism be used?

Answer 22

Energy from oxidation stored in reducing equivalents used COUPLING SYSTEMS directly or indirection such as NADPH and NADH in the mitochondrial system respectively.

Question 23

Through what process is reducing power converted to an energy currency (ATP)

Answer 23

Oxidative phosphorylation

Question 25

Outline the ATP/ADP cycle?

Answer 25

OXYGEN and FUELS are used to combine ADP and Pi producing WATER and CARBON DIOXIDE as waste productions (aerobic respiration). This produces ATP which is used for WORK and dissociates into ADP and Pi again.

Question 26

How much ATP is there in the body at any one time?

Answer 26

250g

Question 27

What do energy signals do and give some examples of high and low forms

Answer 27

Stimulate the anabolic (high energy) and catabolic (low energy) pathways

High E- ATP, NADH, NADPH, FADH2

Low E- ADP, AMP, NAD+, NADP+, FAD

Question 28

How does the body store energy?

Answer 28

As large polymer macromolecules such as glycogen and triglycerides

As CREATINE PHOPSHATE in cells (such as skeletal muscle) which require high energy stores that can be accessed immediately

Question 29

Outline how energy is stored in the form of creatine phosphate

Answer 29

Creatine (Cr) is converted to Phosphocreatine (PCr) by adding a phosphate group from ATP thus creating ADP using the enzyme CREATINE KINASE

Question 30

What is Creatine Kinase a marker for?

Answer 30

For Myocardial Infarction. Released from cardiac myocytes when damaged. Appearing after a few hours. Different ISO forms in skeletal and cardiac allow them to be distinguished (MB subunits vs MM in skeletal)

Question 31

What is creatinine?

Answer 31

Breakdown product of Cr and PCr at a constant rate that is EXCRETED via the KIDNEYS. It is proportional to muscle mass and in urine is a marker of urine dilution.