MEH 1 - Energy Reactions In Cells

Question 1

What is 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 of the body to sustain life

Question 2

What are the two main types of metabolic pathways?

Answer 2

Catabolic pathways and anabolic pathways

Question 3

What is the function of catabolic pathways?

Answer 3

• break down larger molecules into smaller ones
• release large amounts of free energy
• oxidative (release H atoms) and have ‘reducing power’

Question 4

What is the function of anabolic pathways?

Answer 4

• Synthesise larger cellular components from intermediary metabolites
• use energy released from catabolism (ATP)
• reductive (use H released in catabolism)

Question 5

What do metabolised fuel molecules supply?

Answer 5

• building block materials (eg sugars, amino acids, fatty acids)
• organic precursors (acetyl CoA)
• biosynthetic reducing power (eg NADH, NADPH)
• energy for cell function (ATP)

Question 6

Energy is the capacity to do work. What sort of work must be carried out in the body?

Answer 6

• biosynthetic work (anabolism)
• transport work (eg maintenance of ion gradients, nutrient uptake)
• specialised functions (includes mechanical, electrical and osmotic work)

Question 7

How do the standard international unit of energy and the units of energy used for food differ?

Answer 7

The standard international units of energy are Joules or kJ, while food is measured in kcal.

1 kcal = 4.20 KJ

Question 8

Which has the most energy in it - fat, carbohydrate, protein or alcohol?

Answer 8

Fat, then alcohol, then carbohydrate, then protein

Question 9

What is the basal metabolic rate?

Answer 9

Energy required by an awake individual during physical, digestive and emotional rest. Approx. 1400-1700 kcal

Question 10

What is the difference between an exergonic and an endergonic reaction?

Answer 10

Exergonic - releases energy, reaction is spontaneous (catabolism)

Endergonic - requires energy, reaction not spontaneous (anabolism)

Question 11

What are the standard conditions that delta G is usually measured under?

Answer 11

25 degrees C, 1 atm, 1 molar concentration of reactants and products, pH=7

Question 12

What is oxidation?

Answer 12

Removal of electrons or removal of H atoms

Question 13

Give some examples of H-carrier molecules

Answer 13

NAD, NADP, FAD

Question 14

How does ATP concentration affect catabolic/anabolic pathways?

Answer 14

[ATP] high = anabolic pathways are activated

[ATP] low and [ADP/AMP] low = catabolic pathways activated

Question 15

What is phosphocreatine?

Answer 15

A molecule that can phosphorylate ATP in the muscles, in cases where ATP supplies have run out

Question 16

What is creatine kinase used as a marker of?

Answer 16

Used to indicate myocardial infarction. Specific isoform combinations are specific to certain locations, including heart muscle. This means that we can be sure there is heart damage.

Question 17

What is creatinine?

Answer 17

Breakdown product of creatine and creatine phosphate, excreted via kidneys

Question 18

Give some clinical uses of creatinine

Answer 18

• creatinine excretion per 24h is proportional to muscle mass of individual, so provides a measure of muscle mass
• concentration in urine is marker of urine dilation
• can be used to test urinary loss of many substances