Revision questions - week 2 Flashcards
glucose converted to ATP by
glycolysis
acetyl coa
triglycerides converted to ATP by
lipolysis
- broken down into free fatty acids and glycerol
beta oxidation
protein converted to ATP by
deamination (removal of amine group from carbon skeleton)
ethanol converted to ATP by
alcohol dehydrogenase ->acetaldehyde - >acetyl Coa enters TCA cycle and turns to ATP
ATP yield of protein
no yield
ATP yield of glucose
38ATP
ATP yield of triglycerol
30 ATP
ATP yield of ethanol
5 ATP
Explain each pathway in dot points, ensuring that you name the key steps with substrate and product
Metabolic pathways
Anabolic pathways
Catabolic pathways
What molecule sits at the crossroad of energy metabolism?
Acetyl CoA
What are ketone bodies
a molecule formed out of two acetyl coa when there is access in the liver, used in muscle, heart, brain
How/where are ketone bodies formed?
formed in liver from breakdown of fatty acids during periods when fat is the primary source of energy
How/where are ketone bodies used?
in extra hepatic tissues
ketosis
a state with raised ketone bodies in the blood
ketoacidosis
is a metabolic state associated with high concentrations of ketone bodies (life threatening condition - complication of type 1 diabetes)
pathway of gluconeogenesis
Gluconeogenesis starts from oxaloacetate -> Oxaloacetate is formed from glucogenic amino acids carbon backbones( GGAACB), e.g. not fatty acids, or pyruvate -> Pyruvate is formed from glucose or GGAACB, not fatty acids -> Fatty acids are oxidised to acetyl-coA (2 carbons molecules) -> Acetyl coA cannot be converted back to pyruvate (irreversible reaction) -> Acetyl coA enters the CAC to form citrate with oxaloacetate. The CAC is an open cycle /circuit, meaning that the intermediates are formed from a variety of substrates coming from other pathways, and carbons atoms are lost all along as CO2 -> Therefore the acetyl coA 2 carbons do not “exist” by the time oxaloacetate is formed.
Describe the metabolic “shifts” that occur in substrate utilisation for energy production, for maintenance of blood glucose level, and for sparing lean body mass when fasting from a few hours to several days
- ATP production relies on glycogen stores then lean body mas then fat stores and ketone bodies
- Maintenance of BGL – glucose used up, then use liver glycogen, then lean body mass is used in gluconeogenesis to continue supply of BGL.
- Long period of fasting result in using ketone bodies as primary energy source
therefore body does not need to provide as much glucose and can spare lean body mass from being used for gluconeogenesis
Key factors and their roles in the regulation of energy metabolism
- Liver – most reactions take place
- Substrate availability dictates whether anabolic or catabolic
- ATP levels determine activity of AMPK and whether catabolic states are activated
- Enzymes are necessary for reactions
- Hormones dictate whether anabolic (insulin) pathway or catabolic (glucagon) pathway
- Vitamins and minerals necessary for transfer of ions (NAD and FAD) and act as cofactors to metabolism enzymes
Can typical fatty acids be used as substrate for gluconeogenesis? Why? Why not?
- cannot make glucose out of fatty acids
- because the carbons in acetyl acetate are not the same carbons in acetyl coA (lost during the period), it is an open cycle, needs to come from an outside substrate
Substrates(a) Intermediates(b) Products(c)
a) Compounds at the start of the pathway
b) Compounds formed throughout a pathway c) Compounds resulting from the pathway
metabolic pathway
- biochemical reaction occur in progression from substrate to product, usually involving enzymes and cofactors
- Niacin and riboflavin help transfer hydrogens from energy-yielding compounds to oxygen
Anabolic pathway
– Pathways that build molecules and use energy (ATP)
- AA, sugars, FAs, glycerol ->proteins, glycogen, triglycerides and other lipids
Catabolic pathway
– Pathways that break down substrates and produce energy (ATP)
- protein, CHO, fat -> CO2, H2O, NH3
