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[Year 2] Human Metabolism And Clinical Biochemistry > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

What are carbohydrates?

A

Biomolecules that consist of only O,C and H

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2
Q

What is the main source of energy for the body?

A

Carbohydrates

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3
Q

What are the 3 types of carbohydrate?

A

Mono
Di
Poly saccharides

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4
Q

What processes do the carbohydrate nutrients undergo?

A
  • Digestion
  • Absorption
  • Glycolysis
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5
Q

Where does glycolysis occur?

A

It occurs in all human cells

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6
Q

What is the equation of both aerobic and anaerobic glycolysis?

A

Aerobic - Glucose + O2 —> CO2 + H2O + ATP

Anaerobic - Glucose —> Lactate + ATP (or ethanol)

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7
Q

What is glycolysis?

A

The process of turning glucose into ATP through a sequence of enzyme-catalysed reactions

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8
Q

What is the key product formed by glycolysis and why?

A

Pyruvate, it enters the TCA cycle which then gives us ATP

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9
Q

What are the 3 possible fates of pyruvate?

A
  • It can enter the citric acid cycle (TCA cycle) and produce CO2 and H2O [Aerobic glycolysis]
  • It can go through ‘homolactic’ fermentation and produce Lactate [Anaerobic glycolysis]
  • It can go through alcoholic fermentation and produce CO2 and ethanol [Anaerobic glycolysis]
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10
Q

What are the 2 phases of glycolysis?

A

The preparatory phase (Energy investment stage)

The payoff phase (Energy recovery stage)

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11
Q

What happens during the preparatory phase of glycolysis and what is the total ATP yield?

A

Glucose is phosphorylated and converted into glyceraldehyde-3-phosphate

This preparatory phase uses up 2 ATP

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12
Q

What happens in the payoff phase of glycolysis and what is the yield of ATP and NADH?

A

The oxidative conversion of glyceraldehyde-3- phosphate to pyruvate

The yield of ATP and NADH is 4ATP and 2NADH

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13
Q

What is the net yield of products form Glycolysis as a whole?

A

2 ATP + 2NADH + 2 Pyruvate (per one molecule of glucose)

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14
Q

What is the connecting point between Glycolysis and the TCA cycle?

A

When Pyruvate —-> Acetyl CoA

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15
Q

What happens to the pyruvate once is has been produced from glucose?

A

Glycolysis to produce the pyruvate happens in the cytoplasm of the cell, after this pyruvate is transported into the mitochondria and converted into Acetyl CoA which is entered into the TCA cycle (and further oxidised in oxidative phosphorylation)

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16
Q

What is the total yield of products of 1 round of the TCA cycle?

A
  • 2CO2
  • 3NADH
  • 1FADH2
  • 1 ATP/GTP
17
Q

What does the TCA cycle produce metabolites for?

A
  • Gluconeogenesis
  • Fatty acid synthesis
  • Amino acid synthesis
18
Q

What is gluconeogenesis?

A

The synthesuiis of new glucose from non-carbohydrate precursors (eg. Amino acids)

19
Q

When does gluconeogenesis happen in the body?

A

When the body is in a fasting state, low blood glucose

20
Q

What happens in the body when there is a plentiful supply of glucose?

A
  • Glycose metabolism (Glycolysis)

- Glycogen synthesis accelerates

21
Q

Where does gluconeogenesis mainly occur?

A

In the liver

22
Q

What are the precursors that can be converted into glucose?

A
  • Glycolysis products (lactate and pyruvate)
  • Citric acid cycle intermediates (pyruvate)
  • The carbon skeletons of most amino acids
23
Q

What are glycolysis and gluconeogenesis regulated by?

A

Allosteric effects
Phosphorylation
Changes in enzyme synthesis rates

24
Q

What regulates the glucose metabolism as a whole?

A

Hormones

  • Insulin
  • Glucagon
25
Q

What hormone is used when the blood glucose is high?

A

Insulin

26
Q

What hormone acts when the blood glucose is low?

A

Glucagon

27
Q

What does having a lactose intolerance mean?

A

A person is lacking the enzyme b-galactosidase which hydrolyses lactose to galactose and glucose

28
Q

What happens in the body when someone is lactose intolerant?

A

Because lactose isn’t broken down by b-galactosidase the lactose gets fermented in the large intestine by bacteria causing gas and acid production which leads to flatulence and abdominal pain

29
Q

What is the difference between type I and type II diabetes?

A

Type I - The pancreas secretes little or no insulin
Type II - The pancreas produces insulin but the insulin cannot be used efficiently (defective, cannot bind to the insulin receptors)

30
Q

What is the difference in carbohydrate metabolism in a normal healthy cell and a cancer cell?

A
  • Healthy cell - Oxidative phosphorylation (aerobic pathway) or Lactate production (anaerobic pathway)
  • Cancer cell - only anaerobic glycolysis producing lactate (caused by dysfunctional mitochondria)
31
Q

What are the 2 paths that glucose can take in a cancer cell/ tumour?

A
  • Glucose —> Pyruvate —> ‘Dysfunctional’ mitochondria —> reactive oxygen species —> Nuclear DNA instability and DNA damage —> Uncontrolled proliferation
  • Glucose —> Pyruvate —> Lactate
32
Q

What is the Warburg effect?

A

Cancer cells produce lactic acid from glucose even under aerobic conditions (85%)

[Year 2] Human Metabolism And Clinical Biochemistry (7 decks)

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