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Ellie's MEH > Sesh 1- Energy reactions in cells > Flashcards

Sesh 1- Energy reactions in cells Flashcards

1
Q

List the 3 main carrier molecules in their reduced form.

A
  1. NADH
  2. NADPH
  3. FADH2
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2
Q

What sign is delta G of a spontaneous reaction?

A

Negative

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3
Q

Which molecule couples endergonic and exergonic reactions?

A

ATP

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4
Q

High energy signals activate _______ pathways. Low energy signals activate _______ pathways.

A
  1. Anabolic

2. Catabolic

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5
Q

Under what conditions is creatine phosphate formed?

A

High energy conditions.

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6
Q

What can creatinine excretion be used to give an indicator of?

A
  • Skeletal muscle mass
  • Active muscle wasting
  • Renal function
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7
Q

How can urine creatinine and blood creatinine be used?

A

To indicate renal function

i.e. high blood creatinine with low urine creatinine indicates reduced kidney function.

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8
Q

How are creatine and phosphocreatine converted to creatinine?

A

Spontaneously, via a non-enzymatic reaction, at a constant rate.

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9
Q

Which enzyme converts creatine to phosphocreatine?

A

Creatine kinase

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10
Q

What type of sugar is glucose?

A

A hexose sugar

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11
Q

Why can’t cellulose be digested by humans?

A

Lack enzyme to hydrolyse beta-1,4 glycosidic bonds

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12
Q

Why does ingestion of lactose in lactose intolerant patients lead to diarrhoea?

A
  • Cannot be digested, so is present in lumen of colon.
  • Increases osmotic pressure and draws water into lumen of colon
  • Also broken down by colonic bacteria which release gases
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13
Q

What are the 3 types of lactose intolerance?

A
  1. Primary lactase deficiency- in adults that lack lactase persistence allele.
  2. Secondary lactase deficiency- due to injury to small intestine e.g. gastroenteritis. Reversible usually
  3. Congenital- autosomal recessive defect in lactase gene. Can’t digest breast milk
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14
Q

In which tissues is GLUT4 found?

A

Adipose and skeletal muscle

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15
Q

Which transporter uptakes glucose from the small intestine into enterocytes?

A

SGLT1

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16
Q

What can the brain use for energy?

A

Glucose (preferred) and ketone bodies.

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17
Q

Where does glycolysis occur?

A

Cytosol

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18
Q

What is the end product of glycolysis in tissues with mitochondria and oxygen, and how many carbons does it contain?

A
  • 2 Pyruvate

- 3C

19
Q

Which enzyme is responsible for conversion of glucose to glucose-6-phosphate?

A
  • Hexokinase

- Glucokinase in liver and pancreas at high [glucose]

20
Q

Why is glucose phosphorylated in the first step of glycolysis?

A
  • Make it negatively charged so cannot leave cell

- Increases its reactivity

21
Q

Which enzyme catalyses the ‘committing step’ of glycolysis?

A

PFK

22
Q

What does pyruvate kinase do?

A

Catalyses final step of glycolysis, converting PEP to pyruvate

23
Q

In cells without mitochondria or enough oxygen, how is NAD+ regenerated for glycolysis?

A

Pyruvate is reduced to lactate via lactate dehydrogenase.

24
Q

Which enzymes catalyse the 3 rate-limiting steps of glycolysis?

A
  1. Hexokinase
  2. PFK
  3. Pyruvate kinase
25
Q

What is the net ATP production of glycolysis?

A

2 ATP

26
Q

How is hexokinase regulated?

A

Product inhibition

27
Q

Why is the rate of storage of lipid in adipose tissue dependent on glycolysis?

A

DHAP= a glycolysis intermediate used to produce glycerol phosphate- used for TAG synthesis

28
Q

Name 2 ways PFK can be regulated

A
  1. Allosterically- stimulated by high [AMP], inhibited by low [AMP]
  2. Hormonally- insulin stimulates, glucagon inhibits
29
Q

What is the renal threshold for lactate?

A

5 mmol/L

30
Q

Deficiency of which 3 enzymes can lead to galactosaemia?

A
  1. Galactokinase
  2. Uridyl transferase
  3. UDP- galactose epimerase
31
Q

What is galactose reduced to if it accumulates in tissues, and by which enzyme?

A

Galactitol by aldose reductase

32
Q

Why can galactosaemia cause cataract formation?

A
  1. Reduced ROS protection can cause denaturation of crystallin in the lens
  2. Non-enzymatic glycation of lens proteins.
  3. Galactitol increases osmotic pressure, causing lens fibres to swell and rupture
33
Q

What are the 2 major functions of the pentose phosphate pathway?

A
  1. To regenerate NADPH in cytoplasm

2. To produce ribose for nucleotide synthesis

34
Q

What feeds in and out of the pentose phosphate pathway?

A

Glucose-6-phosphate feeds in, and ribose feeds out.

35
Q

What is the rate limiting enzyme of the pentose phosphate pathway, and how is its activity controlled?

A

Glucose 6 phosphate dehydrogenase. Controlled by NADP+/ NADPH ratio.

36
Q

Does NADP+ or NADPH activate glucose-6-phosphate dehydrogenase?

A

NADP+ activates

NADPH inhibits

37
Q

Where does the pentose phosphate pathway occur?

A

Cytosol

38
Q

Which cells are especially affected by a glucose-6-phosphate dehydrogenase deficiency and why?

A

Red blood cells, as the pentose phosphate pathway is their only source of regenerating NADPH.

39
Q

Why can Heinz bodies form in red blood cells in patients with glucose-6-phosphate dehydrogenase deficiency?

A

Cannot regenerate enough NADPH required to recycle Glutathione back to its active form.
This makes red blood cells susceptible to oxidative damage.
Disulphide bonds form between Hb, forming insoluble Heinz bodies.

40
Q

Why can antimalarials cause haemolytic anaemia?

A

They reduce NADPH levels, therefore mean less active GSH can be regenerated, making red blood cells more susceptible to oxidative damage.

41
Q

What does pyruvate dehydrogenase catalyse, and where?

A

Conversion of pyruvate to acetyl CoA in the mitochondrial matrix.

42
Q

Why is pyruvate dehydrogenase sensitive to B vitamin deficiency?

A

It is a multi-enzyme complex that requires 4 B vitamins as co-factors.

43
Q

Why would a pyruvate dehydrogenase deficiency lead to lactic acidosis?

A

Not able to convert pyruvate to acetyl CoA, so acetyl CoA accumulates, and is converted to lactate via lactate dehydrogenase.

44
Q

Why would a cardiac arrest affect the heart and CNS more rapidly than skeletal muscle?

A
  • Heart and CNS have no stores of energy or oxygen

- Skeletal muscle stores creatine phosphate, glycogen and contains myoglobin

Ellie's MEH (12 decks)

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