S4- Energy Reactions In Cells

Question 1

Define:
A) metabolism
B) cell metabolism
C) metabolic pathways

Answer 1

A) the sum of processes which derive energy and raw materials from food studs and use them to support, repair, growth and activity of the tissue of body to sustain life
B) the highly integrated network of chemical reactions in distinct metabolic pathways that occur in cells
C) series of chemical reactions that occur in cells, each stage catalysed by a specific enzyme

Question 2

What are the two types of metabolism and outline what they do?

Answer 2

1. Catabolism: involves the break down of larger molecules into smaller ones
   - releases large amounts of energy coming from bonds
   - oxidative: release h atoms- reducing power
   - produce some intermediary metabolites
2. Anabolism: involves the synthesis of larger molecules from smaller ones
   - uses energy released from catabolism (ATP) to synthesise cell components
   - reductive i.e. use h released in catabolism

Question 3

What are the products of catabolic metabolism?

Answer 3

• Building block materials- sugars, AA, FA
• organic precursors- Acetyl coa (allows for interocnversion of material )
• NADH and NADPH: biosynthetic reducing power
• ATP: energy for cell function

Question 4

A) define energy
b) what defines energy balance?
C) unit of energy

Answer 4

A) capacity to do work
B) average daily intake (food) = average daily expenditure (work, heat)
C) Joule (J)
- 1 KJ= 1000 joules
- 1kcal=4.20 kjoules

Question 5

What are the types of work?

Answer 5

1) biosynthetic work (anabolism): synthesis of cell components
2) transport work: membranes
- maintenance of ion gradients (sodium, potassium, calcium)
- nutrient uptake
3) specialised functions:
- mechanical work: muscle contraction
- electrical work: nervous impulse conduction
- osmotic work: kidney

Question 6

A) what is free energy?

Answer 6

A) the energy released in an exergonic reaction that is available to do work (ΔG)

Question 7

A) what is an exergonic reaction and how would it appear on a energy diagram?

B) what is an endergonic reaction and how would it appear on an energy diagram?

Answer 7

A) a reaction where the energy released is greater than the energy input

• reactions occur spontaneously
• -ΔG
• reactants higher than products

B) a reaction where the energy input is greater than the energy released

• requires energy
• • ΔG
• reactants Lower than products

Question 8

What does the sign of ΔG mean?

Answer 8

Whether the reaction is spontaneous (occurs if sufficient energy)

Question 9

A) what are the major hydrogen carrier molecules?
B) what is their oxidised form?
C) what is their reduced form?

Answer 9

A) NAD, NADP, FAD
B) NAD+, FADP+, FAD
C) NADH + H+, NADPH + H+, FADH2

Question 10

A) What does ATP stand for?
B) What type of molecule is it?
C) what does it consist of?
D) write the equation for the hydrolysis of atp
E) how much energy is released during the hydrolysis of 1 ATP?

Answer 10

A) Adenosine triphosphate
B) phosphorylated nucleotide
C) a nitrogenous base, a pentose sugar and 3 phosphate groups (base always adenine)
D) ATP + h20 —> ADP + pi + energy
E) -31 kJmol-1

Question 11

A) why does there have to be a cycle of ATP and ADP?

Answer 11

A)

• there is a limited concentration of ADP in cells, it is a carrier not a store
• it allows for the controlled release of energy by oxidation
• some of the energy is conserved by forming atp from adp + pi, remainder lost as heat

Question 12

A) what are high energy signals?

B) what are low energy signals?

Answer 12

A) signals that activate anabolic reactions to use up energy

• ATP, NADH, NADPH, FADH2
• i.e. when ATP conc is high anabolic reactions activated to use up energy

B) signals that activate catabolic reactions to release energy

• ADP, AMP, NAD+, NADP+, FAD
• i.e. when ADP and AMP conc high (ATP low), catabolic reactions activated to release energy

Question 13

What are the biological roles of ATP?

Answer 13

• Active transport- selective reabsorption of glucose and AA in kidney
• anabolism
• glycolysis
• movement: muscle contraction and cytoskeleton
• cell division
• heat production

Question 14

A) Some cell types, such as muscles, need to increase metabolic activity quickly. How do they do this and what would they use?
B) why cannot ATP be used?

Answer 14

A)

• They need a reserve of high energy stores that can be used immediately
• They use creatine phosphate

B) ATP cannot be used to store energy for long periods of time, energy is most often stored in form of fuel molecules

Question 15

In muscles, what occurs if:
A) ATP levels are high
B) ATP levels are low

Answer 15

A) phosphate bond energy is stored in phosphocreatine/ creatinephosphate
B) creatine is produced to provide a short term boost of ATP

Question 16

A) write the phosphocreatine equation out in muscles

B) what enzyme catalysts this

Answer 16

A) Creatine + ATP Creatine Phosphate + ADP

B) Creatine Kinase

Question 17

A) What is creatine Kinase?
B) what was it used for clinically?
C) why is it no longer used for this?

Answer 17

A) an enzyme involved in creatine phosphate production, found in skeletal muscle, cardiac muscle and brain tissue
B) to diagnose myocardial infarction- released from cardiac myocyte when damaged, appears in blood
C) no longer used as CK levels are elevated during exercise, endocrine disorders, electrolyte imbalances, drugs, muscular disorders etc.

Question 18

A) What is creatinine?
B) how is it relevant clinically?
C) what would an elevated level indicate?

Answer 18

A) it is a waste product produced via catabolism of phosphocreatine and creatine, filtered by the kidneys
B) any changes in levels of creatinine in the blood are related to excretion and hence reflect kidney function
- measure of muscle mass
- marker of urine dilution
C) dehydration