Protein Metabolism, Turnover and Synthesis Flashcards
(27 cards)
what % of total body protein is turned over daily?
1-3%
what are the four main functions of proteins?
form new muscle cells.
form synthetic pathways.
form plasma proteins, immune cells and haemoglobin.
form new enzymes in the gut and digestive system.
what two processes does protein turnover involve?
protein synthesis and protein degradation.
what is nitrogen balance?
we lose approx 35-100g of protein per day, we need to balance this.
what is a negative nitrogen imbalance?
when there is more breakdown than synthesis.
what is a positive nitrogen imbalance?
when there is more synthesis than breakdown.
what does half life mean?
refers to how long it takes before half of the total amount of protein is broken down, differs in different tissues.
what are proteins made up of?
amino acids (AAs) linked together by peptide bonds.
what is a peptide?
a chain of AAs, usually only about 3 AAs long any longer is a protein.
what are peptide bonds?
covalent bonds formed through a dehydration synthesis (condensation) reaction.
what is the primary structure of a protein?
simply the order of the amino acids.
what is the secondary structure of a protein?
the amino acid chain wraps around itself forming the helix structure proteins are famous for.
what is the tertiary structure of a protein?
the chain of peptides.
what is the quaternary structure of a protein?
assembly of the tertiary subunits.
how do proteins have different functions?
the order of the amino acids allows different proteins to have different functions.
how many functions do proteins have?
there is no protein in the universe which has multiple, every single protein only has one unique function.
why is it useful for the half life to differ in different tissues?
some cells such as those in the liver have a very quick half life, this is useful because the liver is in charge of getting rid of toxic substances therefore getting them gone as quickly as possible whereas others such as mitochondrial and myofibrillar proteins take a long time, this is useful because we could lose all of our muscle overnight if these broke down too quickly therefore it maintains our muscles.
what is hypertrophy and what causes it?
increase in muscle size - going to the gym repetitively. this results from the accretion of new proteins in the muscle fibre.
how does cardio-respiratory training help us to become stronger and fitter?
cardio-respiratory and resistance training can up regulate proteins in skeletal muscles, for growth to take place the muscle protein synthesis must exceed breakdown.
what are genes?
sections of our DNA that code for a specific protein, contain the information required to make new proteins.
explain transcription
transcription takes place when a signal from outside the cell (transcription factor) initiates the duplication of a section of DNA, the double-stranded helix is separated and transcribed by RNA Polymerase II creating the single stranded mRNA. this is replicated via the base pairs matching, A with U, T with A, C with G, and G with C. (adenosine, thymine, uracil, cytosine, guanine - thymine does not occur on RNA therefore A pairs with uracil in transcription)
explain translation
mRNA leaves the nucleus and goes to a ribosome where each codon (three bases) codes for a specific amino acid. the tRNA molecule comes along with matching anticodons and the corresponding amino acids. once the anticodons bond with the codons the amino acid is released forming a chain which will later be folded and create a new protein. this continues until the ‘stop’ codon which means the end of the protein.
how does repeated training cause muscle growth?
when exercise is repeated over time new proteins are formed causing hypertrophy. however, it is not the actual exercise which causes this muscle growth but rather the fact that when we exercise we are actually breaking down muscle, it is therefore the rebuilding process which makes the muscles bigger.
what are the two main pathways for protein degradation?
the lysosomal pathway and the ubiquitin pathway.
