Alimentary - metabolism Flashcards

1
Q

What is catabolic?

A

Breaks molecules down

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2
Q

What is anabolic?

A

Joins molecules together

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3
Q

What is Gibbs free energy?

A

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.

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4
Q

What is the equation for Gibbs free energy?

A

G = H-TS OR G=G products - G reactants

H = heat
T - absolute temp
S - absolute entrophy

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5
Q

What are the two main components that decide if a reaction is spontaneous or not?

A

Inherent free energy change (must be negative)

Mass action

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6
Q

What is mass action?

A

Concentration of products v reactants. More products means G increases, making it less likely to occur

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7
Q

What is ATP?

A

An energy transducer, generated from catabolic reactions. The phosphate bonds contain energy

Break off one or two that can give ATP, ADP or AMP

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8
Q

What is an enzyme?

A

Protein that speeds up a reaction by lowering activation energy (not changing Gibbs) by binding to a side modifying the substrate

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9
Q

What is the lock and key model?

A

The enzyme is sympathetic to the substrate and fit without change

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10
Q

What is the induced fit model?

A

Presence of an enzyme or another substrate lead to changing the shape of the active site, allowing them to fit together.

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11
Q

What is an allosteric substrate?

A

The additional substrate that can change the conformation of the protein binding to it, e.g. Hb and binding of O2 allows more O2

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12
Q

What are the three tiers of metabolic control?

A

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

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13
Q

What is gylcolysis?

A

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

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14
Q

What occurs in glycolysis?

A

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

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15
Q

What is the citric acid cycle?

A

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.

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16
Q

What is the electron transport chain?

A

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)

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17
Q

What disrupts the ECT?

A

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.

18
Q

What happens in anaerobic respiration?

A

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

19
Q

How is carbohydrate stored?

A

Glyogenesis - excess glucose is converted to glycogen which is stored in liver by glycogen synthase.

20
Q

What is glycogenolysis?

A

When theres a demand for glucose, glycogen broken down by glycogen phosphorylase.

Occurs in liver and muscle (in situ use)

21
Q

what is allosteric regulation of glycogenesis/glucogenolysis?

A

G6P upregulates glycogen synthase

ATP and glucose inhibits glycogen phosphorylase

22
Q

What is hormonal regulation of glycogensis/glucogenolysis?

A

Glucagon and noradrenaline/adrenaline up regulate adenylate cyclase

and activate glycogen phosphorylase

23
Q

How are lipids metabolised?

A

TAGs are stored

Lipolysis - uses fat storage

Lipogenesis - creates fat storage

24
Q

How does lipolysis work?

A

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

25
Q

What promotes lipolysis?

A

Glucagon and adrenaline

26
Q

What inhibits lipolysis?

A

Insulin

27
Q

What is ketogenesis?

A

Large amounts of beta oxidation occur in liver but only small amount used for energy.

Excess Acetyl CoA converted into acids + acetone (ketone bodies)

28
Q

What is lipogenesis?

A

FA are combined to form TAG.

29
Q

What inhibits lipogenesis?

A

Glucagon and adrenaline

30
Q

What stimulates lipogenesis?

A

Insulin

31
Q

What is gluconeogenesis?

A

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

32
Q

What are the non-carb sources of gluconeogenesis?

A

Lactate from anerobic glycolysis
Glycerol from TAGs
Glucogenic amino acids
RBCs via cori cycle

33
Q

What is the hormonal control of gluconeogenesis?

A

Glucagon and cortisol up regulate the enzymes in a high

34
Q

What are the liver proteins?

A

Albumin, Globulin, Fibrinogen, CRP, Clotting factors, Thrombopoietin, Angiotensinogen and Amino acids

35
Q

Once cells reach their limit on protein storage, rest of amino acids are metabolised in liver by…

A

Transamination - AA -> Keto-acids

Deamination - glutamate is metabolised further

36
Q

What is the urea cycle?

A

Removes ammonium, and remakes alpha ketoglutarate for use.

37
Q

What happens if there are issues with the urea cycle?

A

Ammonia rises, reversing the reaction of glutamate which builds up causing nervous system issues (is a neurotransmitter)

38
Q

Clinical signs of ammonia toxicity?

A

Intolerance of high protein food
Vomitin
Metal retardation
Coma/death

39
Q

What is GLUT1+3?

A

Always on cells, basal slow uptake and feeds all cells working

40
Q

What is GLUT 5?

A

A receptor on the SI for absorption

41
Q

What is GLUT2?

A

In pancreatic beta cells and hepatocytes, works usually in hyperglycaemia

42
Q

What is GLUT 4?

A

In muscles and adipocytes, working at baseline glucose level. Needs internalised transporters within cells and insulin stimulates this.