Glycolysis Flashcards
Why do we eat?
To maintain cell integrity.
e.g. replace cells that are dying from apoptosis.
What are the main phases of cellular respiration?
Glycolysis
TCA cycle
Electron Transport Chain
What are fats broken down into?
Fatty acids and glycerols
In adipose tissue
Lipolysis breaks down fatty acid into pyruvate and acetyl-CoA.
What are carbohydrates broken down into?
Monosaccharides
In the liver and muscle
Liver stores glycogen and makes pyruvate and acetyl CoA.
What are proteins broken down into?
Amino acids
In the muscle
Produces pyruvate and into the citric acid cycle.
What are complex polymers broken down into?
Polymers or oligomers
Monomers
What happens to lipids in the 4 hours after eating?
Lipids are absorbed into the gut.
Lipids pass into the liver, which packages the triglycerides into Low Density lipoproteins and stores them in the adipose tissue, until needed, or delivered to the muscle.
What happens to glucose in the 4 hours after eating?
Glucose is absorbed into the gut then distributed everywhere - liver, muscles, adipose - primarily the brain as glucose is the main source of energy.
What happens to amino acids 4 hours after eating?
Absorbed into the gut, then delivered to the muscles and used as a fuel source.
What is the structure of glycogen?
Highly branched glucose polymer with a-1,4 and a-1,6 linkages.
Stored as granules in the cytosol of cells.
Where is glycogen found?
High concentration in the liver so it is releasable into the circulation.
N-glycogen is found in muscles for local use during exercise or fasting, as there is no enzyme in muscle to allow glucose to go back into circulation.
How is glycogen regulated?
Synthesis and breakdown are highly regulated by glucagon and insulin through protein phosphorylation cascades which control when glycogen is utilised or stored.
What happens in the fasted state?
4-12hrs after eating:
Adipose tissue releases free fatty acids into circulation to use as fuel.
Brain continues using glucose, taken from glycogen and broken down by liver, then metabolised by the brain.
What is the starved state?
12-20 hours after eating
What do fats do in the starved state?
Accelerated release of free fatty acid from the adipose tissue into the liver to be converted into energy.
What does glucose do in the starved state?
More glucose is released from gluconeogenesis and delivered to the brain.
Ketones can also be used as an energy source.
What do amino acids do in the starved state?
The muscle generates lactate by anaerobic metabolism, and uses amino acids as an energy source.
Transamination of the muscle and liver to detoxify as a result of urea.
What is glucose?
The main energy source.
Generates 28-32 ATP molecules per glucose.
What are the two major elements of glycolysis?
The investment phase - adds 2 ATP to glucose so it can split into 2 molecules.
The Generation/ Pay-off phase - converts 3 C sugars into pyruvate, generates 4 ATP.
Net 2 ATP.
What are the 3 key aspects of the process of glycolysis?
The trap - adding a phosphate
The split - 6 C glucose becomes 2 3C carbon molecules
The pyruvate maker.
What is transamination?
If there is not enough amino acid alanine for gluconeogenesis, pyruvate can be converted by adding NH3, but this forgoes creating energy.
What is anaerobic respiration?
If there is little oxygen available - lactate produced.
Yeast can produce ethanol from it.
What is glucose uptake?
Cells can only take up glucose by facilitated diffusion through hexose transporters.
In many tissues - muscle - major transporter is GLUT4, and made available in plasma membrane through insulin.
What are the steps in the investment phase?
Glucose uses ATP to be converted by hexokinase into glucose-6-phosphate.
Converted to fructose-6-phosphate
Phosphofructokinase uses ATP to convert into fructose 1,6-bisphosphate.
