Week 7: Post Absorptive Metabolism Flashcards
What is an example of nutrients being converted from on form to another?
Fat can be obtained directly from food, or synthesised from protein or CHO
Glycogen as an energy store?
Needed in a hurry stored in the form of CHO
Fat as an energy store?
Huge energy reserve, can be stored in kg quantities
ATP is?
Adenosine triphosphate - present in every cell and contains three phosphate bonds, two of which are high-energy bonds
What is phosphocreatine?
Creatine phosphate - in muscle used to transfer phosphate group to ADP during contraction
Reformed during recovery or when ATP in excess
Flight or fright response is what?
When the body has stored enough ATP and creatine phosphate to supply energy for only a few seconds
What happens when glucose enters the cell?
It is converted into glucose - 6 - phosphate by glucokinase or hexokinase enzymes
What does the liver do to glucose 6 phosphate?
Can convert it back to glucose as it has phosphate enzymes
What are the 4 possible fates of glucose?
- Aerobic metabolism to generate energy when oxygen is available
- Anaerobic metabolism to generate energy when oxygen is limited
- Glycogen synthesis to provide a short term energy store
- Fat synthesis as a long term energy store
What is stage 1 of aerobic glucose metabolism?
Glycolosis.
- occurs in the cell cytoplasm
- conversion of glucose to glucose 6 phosphate then to 2 pyruvate molecules
Produces: 2 ATP and 4H
What is stage 2 of aerobic glucose metabolism?
The conversion of pyruvate to acetyl coA
- after the facilitated transport of pyruvate into the mitochondria by a carrier protein.
Produces 4H but no ATP
What is stage 3 of aerobic glucose metabolism?
The citric acid cycle KREBS CYCLE
- occurs in the mitochondria and produces 16H and 2ATP
What is stage 4 of aerobic glucose metabolism?
Oxidative phosphorylation
- occurs in mitochondria to capture energy from the H atoms and store it as ATP.
- involves the H carrier molecule NAD+
- needs O2
Produces water and 34ATP
What is the total ATP produced from aerobic glucose metabolism??
38 ATP
What limits the amount of glucose taken up by a cell?
Insulin and the capacity of the glucose carrier molecules
What does insulin stimulate?
Glycogen synthesis
Does conversion of glucose to pyruvate require oxygen?
No
what two different fates can pyruvate undergo?
Depending on availability of O2 within the cell, pyruvate can undergo aerobic or anaerobic metabolism
What is produced from anaerobic metabolism?
Lactic acid
Why cant cells stored large amounts of glucose in solution?
Cells would rupture due to high osmotic pressure
What happens in glycogenesis?
Glucose - glucose 6 phosphate - glucose 1 phosphate - uridine diphosphate glucose - glycogen
What happens to excess glucose?
Converted to fat for long term storage
energy for this process is supplied by the pentose phosphate pathway
What is the Pentose Phosphate Pathway?
An independent and cyclical pathway that occurs in liver and fat cells
What happens on each cycle of the penthose phosphate pathway?
6 molecules of glucose enter the pathway and 5 come out (5-C sugar) with one CO2 and H
H atoms can be oxidised to give ATP but normally are used in fat synthesis
Glucose - acetyl coA - fatty acids - triglycerides
