Proteins Flashcards
What are proteins composed of?
Carbon, hydrogen, oxygen and nitrogen
(Body’s main source of nitrogen - 16% weight of protein)
What are amino acids?
Building blocks of protein
Proteins make about 20 amino acids
What is the basic stricture of an amino acid?
central carbon atom, hydrogen atom, amino group, acid group
Fourth bond is distinct side group chain
What are non-essential amino acids?
Body can synthesise them itself
Production is reliant on adequate precursors
11 amino acids
What are essential amino acids?
body cannot make in sufficient amount, must be consumed in diet
9 amino acids
What are conditional essential amino acids?
if body fails to supply/cannot make conversions - a non-essential can become conditionally essential
What is a peptide bond?
A peptide bond link amino acids end to end in a variety of forms
How are amino acid chains formed?
Condensation reactions connect amino acids
Dipeptide - 2 amino acids
Tripeptide - 3
Polypeptide - 50-100
What is the primary structure of amino acid sequence?
Can be linked in a variety of sequences
Determines identity of protein
What is the secondary structure of amino acid sequence?
Determined by weak electrical attractions within polypeptide chain
Positively charged hydrogen atoms attract negatively charged oxygen atoms
Sections twist and fold - strength and identity
What is the tertiary structure - polypeptide tangles?
occurs as long chains that fold/twist into complex tangled shapes
Forms shape to perform function, max stability
What is protein denaturation?
First step in protein breakdown, uncoiling/losing shape of protein - frees amino acids
Occurs when proteins are subject to heat, acid, etc
What are the major gastric enzymes for protein?
hydrochloric acid
Pepsin
Rennin
How are proteins absorbed and transported?
Once inside intestinal cells, amino acids are transported to liver via portal vein
Liver responsible to either
- oxidise for energy
- build new proteins in body
- use as spare spart for other nitrogen containing compounds
What happens in stomach during digestion?
hydrolysis, hydrochloric acid denatures tangles
Converts pepsinogen (inactive) into pepsin (active)
Pepsin cleaves proteins into smaller amino acids
What happens in the small intestine during digestion?
Proteases (from intestine and pancreas) hydrolyse short peptide chains
Peptide enzymes on membrane surface of intestinal cells split into single amino acids
What happens in the transcription of proteins?
Messenger RNA (ribonucleic acid) carries gene code across nuclear membrane into body of cell
Attaches itself to ribosome (protein making machines)
What happens in the translation of protein?
Messenger RNA directs sequences of amino acids to line up for synthesis of protein
Thousands of RNA carry amino acid, cluster and await to unload
Messenger cells can call for specific amino acid, RNA moves into position
How does gene expression come into play with proteins?
Nutrient can play roles in activating or silencing of genes
What are the roles of proteins?
Hormones
Regulate fluid balance
Building material/structure
Enzymes
Acid-base regulator
Transporter (channels/pumps)
Anti-bodies
Source of energy/glucose
What order does the body prefer foods?
Glucose
Fatty acids
Proteins
What is protein turnover?
Proteins being made and broken down to free amino acids
What is the amino acid pool?
When freed amino acid mix with amino acid from diet - forms amino acid pool
When is the nitrogen balance equal, positive and negative?
Equilibrium - nitrogen intake equals nitrogen output
Positive - growing infants, pregnant women, recovering from illness
Negative - people starving, suffering severe stressors (burns, infections, fever)
What other proteins can amino acids make?
Neurotransmitters, serotonin, tyrosine
How are amino acids used for energy and glucose?
when glucose/fatty acids are limited, cells forced to use amino acids for energy
This is why starvation causes wasting of lean body tissue, fat loss
How are amino acids used for glycogen and fat?
when energy intake exceeds demand, excess protein is converted to glucose or ketone bodies, which is stored as glycogen and fat
What are deaminated amino acids?
Stripped of nitrogen containing amino groups
Makes:
Ammonia
Keto acid (used for energy, production of glucose, ketones, cholesterol, fat)
How do you prevent ammonia?
toxic compound - disturbs body’s acid-base balance
Liver combines ammonia with carbon dioxide to make urea
How does the body excrete urea?
Out through urine
Urea is body’s principal vehicle to excrete unused nitrogen
High protein diet - drink lots of water to dilute extreme urea from diet
What is a good way to ensure protein quality?
Contains all essential amino acids in correct proportions to needs of body
Mostly animal foods
Grass fed, butcher
Cooked wel - medium rare, no frying or charring
What is reference protein?
Quality of food protein determined by comparing amino acid composition with requirements of small children
Generates amino acid score
Better the score, more growth will occur
What are complementary proteins?
combining plant protein foods that have different but complementary proteins
All together contain essential amino acids sufficiently
What is PEM and how does it show up?
Protein energy malnutrition
Kwashiorkor - swollen belly, fatty liver
Marasmus - body’s adaptation to starvation
Infection - antibodies decrease to provide amino acids, leaves body vulnerable
What is the protein RDI?
10-35% of diet - protein
What are the drawbacks of protein powders?
Provides no other nutrients needed
If excess protein, body dismantles and stores as fat
Deaminaiton of excess amino acids places extra burden on kidneys to excrete unused nitrogen
What is the downside of amino acid supplements?
body not designed to handle high concentrations
Excess of one amino acid - over demand for carrier that it limits absorption of other amino acids
Can result in deficiencies or toxicity
Where can you find the essential amino acids in the diet?
Fish, meat, eggs, soy, quinoa, buckwheat, hempseed, spirulina
