WEEK 6 Proteins Flashcards
(53 cards)
1
Q
What is the macronutrient protein
A
- a vital structural and working substance in all cells
- both plant and animal sources of protein
- Proteins are made up of amino acids (there are 20 different amino acids with 9 being essential (unable to be made by the body)
2
Q
How the 3 protein sources are absorbed (%)
A
- Animal proteins: 90-99% absorbed
- Plant proteins: 70-90% absorbed
- Soy and legumes: 90% absorbed
3
Q
What are the 7 factors influencing protein requirements
A
- Body size
- Protein quality
- Energy intake adequacy
- New tissue requirement
- Development of muscle mass
- Trauma, stress, infection
- Amino acid antagonism*
4
Q
What is the RDI protein for males
A
0.84 g/kg BM
5
Q
What is the RDI protein for females
A
0.75 g/kg BM
6
Q
What is the RDI protein for athletes
A
1.4-1.7g/kg/day
7
Q
Describe the structure of amino acid
A
- has an amino group, an acid group (“carboxyl end”), a hydrogen atom, carbon atom and a side group
– The sequence of AA in each protein determines its unique shape and function
8
Q
What are the 9 essential amino acids?
A
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
9
Q
What are the 6 conditionally essential amino acids
A
Arginine
Cysteine
Glutamine
Glycine
Proline
Tyrosine
10
Q
What are the 5 non essential amino acids
A
Alanine
Aspartic Acid
Asparagine
Glutamic Acid
Serine
11
Q
What bonds amino acid chains
A
peptide bonds in condensation reactions
12
Q
What are dipeptides
A
2 amino acids bonded together
13
Q
What are tripeptides
A
3 amino acids bonded together
14
Q
Describe the primary structure of protein
A
determined by the sequence of amino acids
15
Q
Describe the secondary strucutre of protein
A
- determined by weak electrical attractions within the polypeptide chain
- positively charged hydrogen atoms attract nearby negatively charged oxygen atoms, sections twist into a helix or fold into a pleated sheet
-> strength and rigidity
16
Q
Describe the teritary structure of protein
A
- Long polypeptide chains twist and fold according to unique side groups of each amino acid
- Hydrophobic – tucked away from water on the inside
- Hydrophilic – outer surface
- Disulphide bridges = link polypeptide chains
17
Q
What are quaternary strucutre of protein
A
- involves the interactions between two or more polypeptides.
– Larger working complexes e.g. haemoglobin
18
Q
What is denaturation
A
-uncoil and lose their shapes, unable to function when subject to heat, acid etc
- eg. hardening of an egg when it is cooked
19
Q
How are proteins digested in the stomach
A
- Hydrochloric acid (HCL) denatures protein tangled strands and converts inactive pepsinogen to pepsin
- Pepsin cleaves proteins to polypeptides and some free amino acids
- Inhibits pepsinogen synthesis
20
Q
How are proteins digested in the small intestine
A
- Pancreatic/intestinal proteases split polypeptides into Tripeptides, dipeptides, amino acids
- Peptidase enzymes on membrane surface – “brush border enzymes” – these ferry AA into intestinal cells.
21
Q
What is the sythesis of a protein determined by
A
genetic information and is unique to individuals
22
Q
What is an amino acid pool
A
consists of all the free amino acids circulating in the body, both those from the breakdown of dietary proteins and those from the body’s own proteins
- Can be used to make new proteins, or they can be stripped of their nitrogen and used as energy
23
Q
What is protein synthesis and 2 processes involved
A
process where cells use genetic instructions (DNA) to create proteins, which are essential for all cell functions and structures
- transcription and translation
24
Q
Describe transcription
A
- stretch of DNA is used as a template to make a strand of RNA (ribonucleic acid) known as messenger RNA.
- mRNA carries the code across the nuclear membrane into body of the cell
- seeks out and attaches itself to one of the ribosomes (a protein-making machine, which is itself composed of RNA and protein)
25
Describe translation
- Situated on a ribosome, messenger RNA specifies the sequence in which the amino acids line up for the synthesis of a protein.
26
Explain the purpose of tRNA
- collect amino acids from the cell fluid and bring them to the messenger
- Each of the 20 amino acids has a specific transfer RNA.
- amino acids line up in the sequence that is called for, and enzymes bind them together
27
What are sequencing errors in protein synthesis
- can cause altered proteins to be made
- An example is sickle-cell anaemia, where an incorrect amino acid sequence interferes with the cell’s ability to carry oxygen
28
Explain the role of proteins in the body - hormones
Regulate body processes and some hormones are proteins – Insulin and glucagon
29
Explain the role of proteins in the body in Building materials for growth and maintenance
A matrix of collagen(protein) filled with minerals -> strength to bones and teeth
- Tissues including the skin, hair, nails and GI tract lining
30
Explain the role of proteins in the body- enzymes
- some proteins act as enzymes
- Proteins that facilitate anabolic (building up) and catabolic (breaking down) chemical reactions
31
How are proteins regulators of fluid balance
– Plasma proteins attract water
– Maintain the volume of body fluids (prevent oedema)
– Protein related causes of oedema:
->Kidney disease
-> Liver disease
-> Inadequate dietary protein
32
What is oedema
Swelling due to an excess of interstitial fluid
33
What is antibodies function
- Fight antigens, such as bacteria and viruses
-> Molecular memory – immunity
34
How do proteins act as acid base regulators
- Proteins, which have negative charges on their surfaces, attract hydrogen ions, which have positive charges
- By accepting and releasing hydrogen ions, proteins maintain the acid–base balance of the blood and body fluids = acts as buffers
35
How do proteins act as transporters in the body
- Carry lipids, vitamins, minerals and oxygen in the body.
- Act as pumps in cell membranes, transferring compounds from one side to the other
36
What is deamination
amino acids stripped of their nitrogen-containing amino group
- Protein is deaminated to create non-essential amino acids or make essential amino acids available
37
4 products that amino acids can make
- Neurotransmitters, for example, adrenaline
– Precursors, for example, for vitamin niacin (from Tryptophan)
– Energy and glucose – causes muscle wasting
– Fat if excess protein consumed
38
What are 2 by products of deamination
ammonia (NH3) & ketoacid (carbon structure without amino gp)
39
Describe the process of deamination and synthesis of a non essential amino acid
an essential amino acid is missing->body may break down some of its own proteins to obtain it
- a particular non-essential amino acid is not readily available, cells can make it from a keto acid if N source is available
- The deamination of an amino acid = ammonia + keto acid
- With ammonia, body can make non essential amino acid w/ keto acid
40
Describe the Transamination and Synthesis of a Non-essential Amino Acid
The body can transfer amino groups (NH2) from an amino acid to a keto acid, forming a new non-essential amino acid and a new keto acid.
- require the vitamin B6 coenzyme.
41
Describe urea synthesis
- Ammonia is toxic to body.
- after deamination, liver combines ammonia+co2=urea
- Liver combines with carbon dioxide = urea.
- Urea cleared from blood by kidneys.
- Adequate fluids required to remove urea from blood.
42
What is function of urea
body’s principal vehicle for excreting unused nitrogen, and the amount of urea produced increases with protein intake
43
What is gluconeogenesis
-glucose production (once amino acid has been deaminated)
- Happens when glucose or FA are limited
44
What does it mean if amino acids are glucogenic
amino acids can be used to synthesise glucose
45
What does it mean if amino acids are ketogenic
amino acids are converted directly to acetyl CoA
46
Can the liver produce non essential amino acids
Yes
47
How many children suffer from PEM worldwide
1 in 4 children worldwide
48
If children are thin for their height, what PEM?
acute PEM (recent food deprivation)
49
If children are short for their age?, what PEM
chronic PEM (long term food deprivation)
50
What countries are PEM prevalent
Africa, Central America, South America, E and SE Asia
51
What is the PEM syndrome marasmus(longterm)
–-infancy, 6 to 18 months of age
- Severe deprivation or impaired absorption
- Develops slowly (chronic PEM)
- Severe weight loss
- Muscle wasting (inc heart)
- < 60 % weight-for-age
- Anxiety and apathy
- Normally good appetite
- Hair and skin problems
52
What is the PEM syndrome Kwashiorkor
-18mths–2yrs
– Infections
– Rapid onset (acute PEM)
– Some muscle wasting, some fat retention
- Growth 60–80% weight-for-age
- Oedema and fatty liver
- Apathy, misery, irritability
- Loss of appetite
- Hair and skin problems
53
What are the 6 impact of too much protein
- No benefits
- Heart disease
-> Processed meats?
-> Homocysteine levels increase cardiac risks
- Cancer
-> A high intake of animal protein is associated with some cancers.
-> high red meat intake (>160 g/d)=↑risk colorectal cancer
- Gout
- Adult bone loss (osteoporosis)
->High protein intake associated with increased calcium excretion
- Weight control
-> Protein at each meal provides satiety
-> Adequate protein, moderate fat and sufficient carbohydrate better support weight loss
- Kidney disease
-> High protein intake increases the work of the kidneys
