Lecture 3 Flashcards
What are carbohydrates?
Biomolecules that consist of only O,C and H
What is the main source of energy for the body?
Carbohydrates
What are the 3 types of carbohydrate?
Mono
Di
Poly saccharides
What processes do the carbohydrate nutrients undergo?
- Digestion
- Absorption
- Glycolysis
Where does glycolysis occur?
It occurs in all human cells
What is the equation of both aerobic and anaerobic glycolysis?
Aerobic - Glucose + O2 —> CO2 + H2O + ATP
Anaerobic - Glucose —> Lactate + ATP (or ethanol)
What is glycolysis?
The process of turning glucose into ATP through a sequence of enzyme-catalysed reactions
What is the key product formed by glycolysis and why?
Pyruvate, it enters the TCA cycle which then gives us ATP
What are the 3 possible fates of pyruvate?
- 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]
What are the 2 phases of glycolysis?
The preparatory phase (Energy investment stage)
The payoff phase (Energy recovery stage)
What happens during the preparatory phase of glycolysis and what is the total ATP yield?
Glucose is phosphorylated and converted into glyceraldehyde-3-phosphate
This preparatory phase uses up 2 ATP
What happens in the payoff phase of glycolysis and what is the yield of ATP and NADH?
The oxidative conversion of glyceraldehyde-3- phosphate to pyruvate
The yield of ATP and NADH is 4ATP and 2NADH
What is the net yield of products form Glycolysis as a whole?
2 ATP + 2NADH + 2 Pyruvate (per one molecule of glucose)
What is the connecting point between Glycolysis and the TCA cycle?
When Pyruvate —-> Acetyl CoA
What happens to the pyruvate once is has been produced from glucose?
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)
What is the total yield of products of 1 round of the TCA cycle?
- 2CO2
- 3NADH
- 1FADH2
- 1 ATP/GTP
What does the TCA cycle produce metabolites for?
- Gluconeogenesis
- Fatty acid synthesis
- Amino acid synthesis
What is gluconeogenesis?
The synthesuiis of new glucose from non-carbohydrate precursors (eg. Amino acids)
When does gluconeogenesis happen in the body?
When the body is in a fasting state, low blood glucose
What happens in the body when there is a plentiful supply of glucose?
- Glycose metabolism (Glycolysis)
- Glycogen synthesis accelerates
Where does gluconeogenesis mainly occur?
In the liver
What are the precursors that can be converted into glucose?
- Glycolysis products (lactate and pyruvate)
- Citric acid cycle intermediates (pyruvate)
- The carbon skeletons of most amino acids
What are glycolysis and gluconeogenesis regulated by?
Allosteric effects
Phosphorylation
Changes in enzyme synthesis rates
What regulates the glucose metabolism as a whole?
Hormones
- Insulin
- Glucagon
What hormone is used when the blood glucose is high?
Insulin
What hormone acts when the blood glucose is low?
Glucagon
What does having a lactose intolerance mean?
A person is lacking the enzyme b-galactosidase which hydrolyses lactose to galactose and glucose
What happens in the body when someone is lactose intolerant?
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
What is the difference between type I and type II diabetes?
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)
What is the difference in carbohydrate metabolism in a normal healthy cell and a cancer cell?
- Healthy cell - Oxidative phosphorylation (aerobic pathway) or Lactate production (anaerobic pathway)
- Cancer cell - only anaerobic glycolysis producing lactate (caused by dysfunctional mitochondria)
What are the 2 paths that glucose can take in a cancer cell/ tumour?
- Glucose —> Pyruvate —> ‘Dysfunctional’ mitochondria —> reactive oxygen species —> Nuclear DNA instability and DNA damage —> Uncontrolled proliferation
- Glucose —> Pyruvate —> Lactate
What is the Warburg effect?
Cancer cells produce lactic acid from glucose even under aerobic conditions (85%)
