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57 Cards in this Set

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Total body mass of proteins

10kg

Where is protein turnover higher in g/day? in %/day? Where else is protein turnover occurring?

Skeletal muscles: 120g/day (2%/day)


Liver: 80g/day (10%/day)


Small intestine: 70g/day (14%/day)

How do AA get into cells?

Secondary active transport (sodium co-transport down concentration gradient followed by Na/K ATPase to remove sodium)



Name the keto-acid corresponding to the following amino acids: alanine, glutamate, aspartate

Alanine: pyruvate

Glutamate: alpha-ketoglutarate


Aspartate: Oxaloacetate


All three are part of the glycosis-TCA cycle pathway

Function of glutamine

Nitrogen carrier

Two synonyms of keto-acids

2-oxoacids


Carbon skeleton

Name three nitrogenous waste products of the body and their origin (i.e. the result of what product's break down)

Urea from degradation of AA


Uric acid from degradation of A and G bases


Creatinine from degradation of creatine phosphate

Name three consequences of increased uric acid

Risk of gout


Risk of T2D


Uric acid kidney stones

Three categories of AA based on their metabolic role

Ketogenic


Glucogenic


Mixed

Name 5 glucogenic AA

Alanine


Aspartate


Glutamate


Glutamine


Glycine

Name 1 ketogenic AA

Leucine

Name 1 mixed (keto/glucogenic) AA

Tyrosine

In what two organs does oxidative deamination occur?

Liver


Kidney

What is particular about the deamination of glutamate? What role does it play in metabolism?

Glutamate can undergo uncoupled deamination to alpha-ketoglutarate releasing NH3 which can be excreted in urea. This process can also be coupled with the transamination of another AA used for metabolism

Glutamate can undergo uncoupled deamination to alpha-ketoglutarate releasing NH3 which can be excreted in urea.

This process can also be coupled with the transamination of another AA used for metabolism





What enzyme catalyses the deamination (not transamination) of glutamate?

Glutamate dehydrogenase

Outline the link between glutamate and glutamine and explain why generating one from the other may be useful.

Glutamate + ATP + NH4 ➙ Glutamine + ADP + Pi




Generating glutamine


Non-toxic transport of NH4




Generating glutamate


Generate energy


Use as a neurotransmitter

Why is ammonium toxic (4 causes)?

Two reactions


alpha-ketoglutarate + NH4 + NADH ⇌ glutamate + NAD+


glutamate + NH4 ⇌ glutamine




Consequences


1) NH4 increases ⇒ NADH decreases ⇒ O2 not reduced in ETC ⇒ oxidation of tissue


2) NH4 increases ⇒ alpha-ketoglutarate decreases ⇒ TCA cycle compromised


3) NH4 increases ⇒ glutamate decreases ⇒ loss of neurotransmitter


4) NH4 increases ⇒ glutamine increases ⇒ cerbral cell swelling

Formula of ammonium and ammonia

Ammonium: NH4+


Ammonia: NH3

Where does urea created in the liver go?

Dissolve in blood

Show how the ammonium is transformed into urea and outline the different compartments in which this takes place.



Outline the pathophysiology of hepatic encephalopathy

Liver failure ⇒ Ammonia is not more excreted

Outline the three paths through which purines are broken down

Note: Inosine is the I nucleoside that can swap with other base in tRNA under Wobble hypothesis.

Note: Inosine is the I nucleoside that can swap with other base in tRNA under Wobble hypothesis.

How are pyrimidines broken down?

General: Pyrimidines ➙ Beta AA + CO2 + NH4+




E.g.: Cytosine ➙ Uracil ➙ Beta-alanine+CO2+NH4+

Three methods to generate purine and pyrimidines

1. Absorption from diet


2. Biosynthesis from glutamate (for pyrimidines) or sugar phosphate (for purines)


3. Salvage from breakdown of existing nucleotides

Outline the glucose-fatty acid cycle and explain its utility.

Ensures that either FA or glucose is used by muscle as a source of energy and not both.

Ensures that either FA or glucose is used by muscle as a source of energy and not both.

Outline how the glucose-fatty acid cycle is implemented at the cellular level in muscles.



Outline the steps of intracellular signalling of insulin



How does urinary nitrogen evolves during the first month of fasting ? Why?

Urinary nitrogen decreases linearly during fasting because, although protein progressively becomes the only source of energy (producing more nitrogen per kcal), metabolic rate also decreases exponentially (reducing the amount of kcal used).

How do plasma NEFA and KB evolves during the first month of fasting?



Name two processes that occur in the kidney during fasting and outline how they are coupled.

1) Trapping of H+ for pH regulation
2) Gluconeogenesis

1) Trapping of H+ for pH regulation


2) Gluconeogenesis

How do thyroid hormones adapt to fasting/starvation?

They decrease to decrease basic matabolic rate

Name three main substrates of gluconeogenesis during starvation and name their tissue origin.

Lactate (from anaerobic metabolism in renal medulla, RBC, etc.)


Alanine (from muscles)


Glycerol (from breakdown of TAG)

Evolution of ATP in muscle fibres during the first 20s of contraction. What other concentration explains this evolution?



Difference in source of energy between intense and light aerobic exercise

Intense aerobic: carbohydrates early on followed by NEFA from adipose tissue




Light aerobic: NEFA from adipose tissue all the time

What is the main source of glucose during intense exercise?

Glycogenolysis in the muscles

(Plasma glucose is low and blood flow to liver is low due to vasoconstriction)

Name 6 effects of catecholamines during exercise

Increase HR


Increase heart contraction force


Increase blood flow to skeletal muscles


Decrease blood flow to internal organs


Increase lipolysis in adipose tissues (Hormone sensitive lipase)


Stimulates glycogenolysis

How does insulin level evolve during exercise? Why?

Because of alpha2 adrenergic receptor in the pancreas

Because of alpha2 adrenergic receptor in the pancreas

Role of glucagon during exercise

No significant role

Show how insulin, TAG, lactate, cortisol, catecholamine, and glucose evolve during aerobic exercise



How does skeletal and cardiac muscle cells manage to capture blood glucose during exercise?

GLUT4 are activated by muscle contraction


(Insulin is low so the stimulus of interest is muscle contraction)

What is the principal energy source that is used during the last second of a sprint?

Glucose from glycogen breakdown

What is the principal energy source that is used during the last minute of a 2 hours jogging

Fatty acid delivered to muscles from adipose tissues by albumin

Name two AA that play a specific role in exercise and explain that role

Glutamine: regulate pH (deliver NH3 to kidney which can trap H+)


Alanine: substrate for gluconeogenesis

What source of energy does the foetus mostly use?

Glucose

When in development (from embryo to puberty) do we start beta-oxidation, ketogenesis, and gluconeogenesis?

At birth

How is plasma [HDL] in T2D and why?

[HDL] decrease because insulin loses its effect on lipid metabolism

How is insulin concentration in pre-T2D and in during T2D?

Pre-T2D: increased compared to normal (compensatory mechanism)


T2D: decreased insulin

Why is NEFA increased in the blood of patients with diabetes mellitus

A. Release of NEFA from adipose tissues is unrestrained (see glucose-FA cycle)




B. Hormone-sensitive lipase is not inhibited by insulin.

Name one stimulus and one inhibitor of hormone-sensitive lipase in adipose tissues.

Activation: catecholamines


Inhibition: insulin

Where is insulin injected (tissues)?

In subcutaneous adipose tissues

Define respiratory quotient. Why is it useful?

CO2 eliminated/O2 consumed


Useful to distinguish between a state of carbohydrate metabolism (RQ=1) and a state of fat metabolism (RQ=0.7).

Respiratory quotient for carbohydrate.

1

Respiratory quotient for fat.

0.7

Why is the RQ for fat lower than the RQ for carbohydrate?

Because FA (2n carbon) are transformed to acetyl-CoA (2 carbons + CoA carbons) without production of CO2 whereas glucose (6C) is transformed into pyruvate (3C) which is itself transformed into acetyl CoA (2C) with the production of one CO2.

RQ for proteins

0.8-0.9

Max value of RQ

Undefined; can be much larger than 1

How to remember which AA are ketogenic, which are glucogenic and which are both?

Non-essential


All glucogenic and tyrosine is also ketogenic




Essential


Gluogenic: "Val and his Three methods" (Valine, Histidine, Threonin, Methionine)


Ketogenic: "In lieu of lysine" (Leucine, Lysine)


Both: "Illy Trapped both pheasants" (Isoleucine,Tryptophan, Phenylalanine)