Protein metabolism Flashcards
basic process
- what initiates it and where
- what is released in the next place
- what does this result in and what happens to them
- in the stomach initiated by pepsin and hydrochloric acid
- pancreatic proteases and enterocyte proteases are secreted in the small intestine.
- peptide fragments and free amino acids that are absorbed by the small intestine.
where do amino acids produced during digestion go
- Gut/gastrointestinal tract extracts 40-50% of all amino acids.
- Remaining AAs enter the hepatic portal vein and are taken up by the liver.
how many aas are used for energy
- ~40% is then catabolized via ureagenesis for energy
digestion in the stomach more detail
- how are the proteins denatured
- what hydrolysis the proteins peptide bonds
- what secretes these things
- highly acidic environment (pH 1.5-3.5)
- hydrochloric acid and the enzyme pepsin making smaller proteins
- secreted by gastric glands and mix in the gastric juice
how does pepsin become active
When pepsinogen and hydrochloric acid mix in the gastric juice, pepsinogen unfolds forming active enzyme pepsin
digestion in the small intestine more detail
- how are denatured proteins neutralised
- why does this happen
- how are denatured proteins degraded to AAs
- what are AAs used for
- enzyme secretin which acts on the pancreas to secrete bicarbonate.
- protects the intestinal wall from the high acid stomach acids.
- by 6 enzymes to (tri/di)peptides, then into single AAs via specific protease enzymes (for each tri/dipeptide)
- enter circulation for use as a substrate for energy or protein synthesis.
the protein content of the human body
- how vastly present are proteins
- what per cent of male and female mass is protein
- present in every cell in the body, as well as extracellular fluids
- Men = 16% total protein
- Women = 14% total protein
- due to women having more adipose tissue
protein synthesis
- what is the process called
- process
- anabolic signalling
- Amino acids are sensed and Transported across the muscle cell membrane via SNAT2 & LAT1.
- stimulating a cascade of protein signalling and phosphorylation (activation) via Sestrin-2.
- mTOR is translocated to the lysosome to become ‘active’.
- mTOR then phosphorylates several proteins (S6K1, RPS6, 4E-BP1) to initiate protein translation at the ribosome (mRNA), subsequently increasing protein synthesis.
protein breakdown
- process
- Proteins are marked for degradation by the attachment of E3 ubiquitin ligases MuRF1 and MAFbx
- the ubiquitin is recognized and degraded by a protease complex, called proteasome.
relationship between protein synthesis and breakdown in healthy compared to older/diseased
- healthy about equal so zero protein balance so protein mass remains stable
- not case for old/diseased
impact of Exercise on protein turnover and net balance
- relationship between breakdown and synthesis in a fasted state
- relationship between breakdown and synthesis following exercise
- relationship between breakdown and synthesis in a fed state
- breakdown exceeds synthesis so is. negative net balance
- both protein synthesis and breakdown increase. However, a negative net balance is still apparent.
- synthesis far exceeds protein breakdown, and a positive protein balance
amino acid degredation
- how do amino acids produce energy
- what is the first step of aa degradation
- what 4 things can happen to glutamate
- what by-product is formed during oxidative deamination
- enter the citric acid cycle at various points following degradation (in the liver) to support energy demand
- most amino acids transfer their amino group to aketoglutarate by transamination, producing glutamate
- enter the citric acid cycle to produce aerobic energy, convert back to a-ketoglutarate by losing the amino group via oxidative deamination (via glutamate dehydrogenase), can be converted to glutamine by adding an amino group which then disposes amino groups in other tissues, glutamate can transaminate to pryruvate forming αlpha-ketoglutarate and alanine
- amino acid from glutamate is given off in the form of ammonia which is converted to urea and excreted during the urea cycle
how many amino acids are
- glucogenic (can produce glucose)
- ketogenic
- both glucogenic and ketogenic
- 14
- 2
- 4
transamination
- what is it
- what enzyme catalyses it
- what keto acid is most commonly involved
- transfer of an amino acid from 1 molecule to another
- aminotransferase
- alpha ketoglutarate
deamination
- what is it
- what happens to the thing removed
- The amino acid removal of its amino group.
- Ammonia is formed and converted into urea in the liver, it is excreted in urine and sweat.
