Alimentary - metabolism Flashcards
What is catabolic?
Breaks molecules down
What is anabolic?
Joins molecules together
What is Gibbs free energy?
A value that defines how spontaneous a reaction is, with a negative value meaning the reaction is spontaneous, and a positive value meaning the reaction is non-spontaneous.
What is the equation for Gibbs free energy?
G = H-TS OR G=G products - G reactants
H = heat
T - absolute temp
S - absolute entrophy
What are the two main components that decide if a reaction is spontaneous or not?
Inherent free energy change (must be negative)
Mass action
What is mass action?
Concentration of products v reactants. More products means G increases, making it less likely to occur
What is ATP?
An energy transducer, generated from catabolic reactions. The phosphate bonds contain energy
Break off one or two that can give ATP, ADP or AMP
What is an enzyme?
Protein that speeds up a reaction by lowering activation energy (not changing Gibbs) by binding to a side modifying the substrate
What is the lock and key model?
The enzyme is sympathetic to the substrate and fit without change
What is the induced fit model?
Presence of an enzyme or another substrate lead to changing the shape of the active site, allowing them to fit together.
What is an allosteric substrate?
The additional substrate that can change the conformation of the protein binding to it, e.g. Hb and binding of O2 allows more O2
What are the three tiers of metabolic control?
Mass action affects free energy
Enzymes are controlled by:
-One rate controlling enzyme
- Amount of enzyme + activity level (allosterically and/or by reversible covalent modification controlled hormones)
-Direction of pathway set by irreversible actions
What is gylcolysis?
Conversion of glucose to energy, without O2 (anerobic and aerobic)
Occurs in all tissues, but primarily the liver and muscles.
Can enter through glucose, glucogenolysis and other monosaccharides
What occurs in glycolysis?
Blood glucose
Hexokinase | (irreversible) ADP
G-6-P
|
F-6-P
PFK | (irreversible) ADP
F-1,6-P
|
| 2xATP and 2xNADH+H+
|
2x PEP
Pyruvate kinase | 2xATP
2x Pyruvate
| (irreversible) CO2 and NADH + H+
Acetyl CoA
What is the citric acid cycle?
Acetyl CoA is used into the citric acid cycle. It creates most of the ATP.
Citrate goes to alpha ketogenesis and to OAA.
Output is 2xCO2, 3xNADH, 3x H+, FADH2 and GTP
The NADH produced goes to electron transport chain.
What is the electron transport chain?
Operates under aerobic conditions, requires a supply of NAD+ and FAD.
In mitochondria wall, with 5 carrier protein complexes. As the electrons pass into the complexes, energy is created to pump H+ in to the intramembranous space creating a protein motive force.
This then re-enters the matrix via ATP synthase creating ATP (most of it)
What disrupts the ECT?
Uncoupling agents, provide alternative routes for protons to pass into the matrix, without going through ATP synthase. Less ATP is created but does create heat.
What happens in anaerobic respiration?
No O2 = no ETC.
Excessive NADH and pyruvate.
Pyruvate is converted to lactate which is converted back to pyruvate (in liver ) by NADH allowing glycolysis to continue
How is carbohydrate stored?
Glyogenesis - excess glucose is converted to glycogen which is stored in liver by glycogen synthase.
What is glycogenolysis?
When theres a demand for glucose, glycogen broken down by glycogen phosphorylase.
Occurs in liver and muscle (in situ use)
what is allosteric regulation of glycogenesis/glucogenolysis?
G6P upregulates glycogen synthase
ATP and glucose inhibits glycogen phosphorylase
What is hormonal regulation of glycogensis/glucogenolysis?
Glucagon and noradrenaline/adrenaline up regulate adenylate cyclase
and activate glycogen phosphorylase
How are lipids metabolised?
TAGs are stored
Lipolysis - uses fat storage
Lipogenesis - creates fat storage
How does lipolysis work?
Tags hydrolysed into FA and glycerol by triglyceride lipase
FA bind to albumin, making them insoluble transported to tissues and liver
Enter the hepatocytes and converted to glycerol-3-phosphate entering glycolysis
and the FA undergoes beta oxidation in mitochondria
What promotes lipolysis?
Glucagon and adrenaline
What inhibits lipolysis?
Insulin
What is ketogenesis?
Large amounts of beta oxidation occur in liver but only small amount used for energy.
Excess Acetyl CoA converted into acids + acetone (ketone bodies)
What is lipogenesis?
FA are combined to form TAG.
What inhibits lipogenesis?
Glucagon and adrenaline
What stimulates lipogenesis?
Insulin
What is gluconeogenesis?
Formation of glucose from non-carb sources occurs after 8 hours of fasting, when glycogen stores deplete or an alternative source of glucose is required.
Happens in liver and in cortex of kidney
Uses 6 ATP
What are the non-carb sources of gluconeogenesis?
Lactate from anerobic glycolysis
Glycerol from TAGs
Glucogenic amino acids
RBCs via cori cycle
What is the hormonal control of gluconeogenesis?
Glucagon and cortisol up regulate the enzymes in a high
What are the liver proteins?
Albumin, Globulin, Fibrinogen, CRP, Clotting factors, Thrombopoietin, Angiotensinogen and Amino acids
Once cells reach their limit on protein storage, rest of amino acids are metabolised in liver by…
Transamination - AA -> Keto-acids
Deamination - glutamate is metabolised further
What is the urea cycle?
Removes ammonium, and remakes alpha ketoglutarate for use.
What happens if there are issues with the urea cycle?
Ammonia rises, reversing the reaction of glutamate which builds up causing nervous system issues (is a neurotransmitter)
Clinical signs of ammonia toxicity?
Intolerance of high protein food
Vomitin
Metal retardation
Coma/death
What is GLUT1+3?
Always on cells, basal slow uptake and feeds all cells working
What is GLUT 5?
A receptor on the SI for absorption
What is GLUT2?
In pancreatic beta cells and hepatocytes, works usually in hyperglycaemia
What is GLUT 4?
In muscles and adipocytes, working at baseline glucose level. Needs internalised transporters within cells and insulin stimulates this.
