Lecture 6 - Protein: Amino Acids Flashcards
What is a protein?
Large complex molecules composed of amino acids
What do all amino acids have in common?
Central C H Acid group Amino Group Unique side group
Where does our body main source of Nitrogen come from?
Amino acids
What are the 2 groups of amino acids?
Essential/indispensable and Nonessential/dispensable
What is an essential amino acid?
One that we have to consume in our diet because our body cant make it or cant make it in high enough quantities that our body needs
What is the process in which Amino acids are formed?
Condensation reaction
Where are proteins stored?
Our bodies don’t have storage for protein
-they are all being used and have some type of function
What is he process in which proteins are made?
An mRNA is made from DNA. mana comes out of the nucleus and ribosomes bind at many different places on the mRNA and tRNA comes and brings the appropriate amino acid that is next in the protein sequence
How many structures are there for proteins?
4 Primary Secondary Tertiary Quaternary
What is the primary structure of proteins?
Simply the sequence of amino acids
-not a functional protein
What is the secondary structure of proteins?
Twisting/folding in the chain determined by weak electrical attractions within the chain
-provides strength and rigidity
What is tertiary structure of proteins?
Complex structures due to side chain properties
-3D shape either fibrous (structural) or globular (transportation)
What is Quaternary Structure of proteins?
Interaction between polypeptide chains. 2 or more chains being stuck together
-functional protein
What is protein denaturation?
When a proteins stability is disturbed, which causes the protein to lose its shape and function
What are some forms of denaturation?
Heat Acids and Bases Heavy Metals Alcohol Other damaging substances
Which proteins are dented from which substance?
Every protein will be susceptible to different forms of denaturation in different ranges
Ultimately what does denaturation result in?
An irreversible loss in protein function
-primary structure usually still there
Is there digestion of proteins in the mouth?
No
What happens to protein digestion in the stomach?
HCl denatures proteins and activates pepsin which is a non specific protease cutting peptide chains into smaller ones
What happens to protein digestion in the small intestine?
Pancreas and cells in the intestines release enzymes to further breakdown the protein
What are the 2 important enzymes that are important for protein digestion in the small intestine?
Tripsin: cleaves peptide chain only at lysine and arginines
-inhibits its own production
Chymotripsin: Also cleaves at certain amino acids
How are proteins absorbed?
Amino acids must be transferred into intestinal cells via specific carriers for amino acids and small peptides
-one carrier for a couple specific amino acids
What are the 2 things that can happen to amino acids after they are in the intestinal cells?
- Used for energy
2. Used for synthesis of other compounds
When proteins are absorbed and not used where do they go?
Sent to the liver via the blood stream
Why do we need proteins?
Cell growth, repair and maintenance Hormones Enzymes Electrolyte balance pH balance Transporters Antibodies Energy source
Why are proteins and fluid balance important?
Proteins attract waster and are found in cells and in plasma. Don’t normally cross the cell membranes and therefore fluid accumulates in the tissues
Why are proteins important in acid-base balance?
Low proteins lead the environment to be more acidic or basic which disturbed protein function by altering blood pH.
Why are proteins important in antibodies?
Antigens are destroyed by antibodies. Molecular memory is called immunity. If there is a low intake in protein then you have a weakened immune system
-each antigen has a specific antibody to protect the body from being sick
Why are proteins important in energy?
Proteins can be sacrificed when needed for energy (4kcal/g of protein)
-protein needs to go through deamination, creating ammonia and is excreted through the kidneys
What is protein turnover?
The continual making and breaking down of proteins
How is the protein turnover constant?
There is an amino acid pool which remains constant within our cells to use and make other proteins or use for energy purposes
What is the N balance?
Where there is nitrogen equilibrium
-N in the body = N out
What is a +N balance?
When consuming more nitrogen then excreting
What is a -N balance?
When losing more nitrogen than they are taking in
What can we make out of amino acids?
Other compounds (neurotransmitters)
Energy and glucose
Fat
-amino acid needs to be deaminated
After deamination what are you left with?
Ammonia and the remaining carbon structure (Keto acid) which is used for energy to make glucose or non essential amino acids or Acetyl CoA
What determines protein quality?
Digestibility
Amino Acid Composition
What is protein digestibility dependent on?
Source of foods eaten
Animal protein: 90-99% digestibility (not a bunch of fibre)
Soy and legume protein: >90% digestibility (has more fibre, harder to digest because we don’t have the enzymes)
Plant protein: 70-90% digestible (veggies, nuts and seeds)
What determines protein quality in terms of amino acid composition?
Must have all 9 essential amino acids because we can not make these
-partial proteins aren’t a thing
What is a strategy used to ensure you get a complete set of amino acids?
Complementary proteins
-combining proteins from different sources to create full amino acid complement
What is PDCAAS?
Protein Digestibility corrected amino acid score
-measures protein quality based on digestibility and essential amino acid profile on a 0-100 scale
Which foods are 100 on the PDCAAS?
Egg whites Ground beef Chicken Skim milk Tuna
What is the AMDR protein recommendation?
10-35% total daily energy intake
What is the RDA protein recommendation?
0.8g/kg body weight/day
Which groups of people require more protein?
Children, pregnant women, Athletes and vegetarians (more because they are less digestible)
What are the 6 types of vegetarian diets?
Semivegetarian/flexitarian Pescovegetarian Lacto-ovo-vegetarian Lacto-vegetarian Ovovegetarian Vegan
What is a Semivegetarian?
Excludes or limits red meat, may also avoid other meats
What is a Pescovegetarian?
Only eat fish
What is a Lacto-ovo-vegetarian?
Excludes animal flesh and seafood
-eats eggs and dairy products
What is a lacto-vegetarian?
Excludes eggs
-consumes dairy products
What is an Ovovegetarian?
Excludes dairy products, flesh and seafood products
-consumes eggs
What is a Vegan?
Only consumes plant based foods
-may be B12, zinc, iron and calcium deficient
Why do people become vegetarians?
Religious reasons Ethical reasons Food safety Ecological reasons Health benefits
Wha are the health benefits of becoming a vegetarian?
Lower intake of fat and total energy, blood pressure
Reduced risk of heart disease, cancer, kidney disease
Fewer digestive problems (higher fibre intake)
What are some challenges with a vegetarian diet?
Can be low in Fe, Ca, Zn, Vitamin D B2 B12
Need to have complementary proteins
Where can vegetarians obtain possible missing B12, D B2 (riboflavin), Fe, Ca and Zn?
B12-fortified grains, nutritional yeast
D- Fortified milk products, fatty fish, sun (D3 better)
B2-Dairy, enriched whole grains, legumes veggies nuts and seeds
Fe-whole grains, dried fruit, leafy veggies, beans, nuts
Ca- dairy alternatives fortified with calcium, almonds, leafy veggies
Zn- who grains, wheat germ, beans, nuts and seeds
What is PEM?
Protein-Energy Malnutrition
- insufficient intake of protein, energy or both
- mostly impact children
What is Kwashiorkor?
“The sickness the baby baby gets when the new baby come”
- results from inadequate protein intake
- affects older infants
What are the symptoms of Kwashiorkor?
Happens fast
Some weight loss (usually hidden by edema)
Muscle wasting
80% growth for weight and age
Enlarged fatty liver (results in distended abdomen)
Loss of appetite
What is Marasmus?
Chronic Deprivation of protein
-occurs in children less than 24 months
What are symptoms of Marasmus?
Weight loss
Muscle wasting
How does one die from PEM?
By infection from degradation of antibodies
How do you cure PEM?
It is reversible with rehydration, electrolyte balance and gradually adding protein into the diet
What population does PEM also effect?
Poverty, Elderly Homeless Eating disorders AIDS/Cancer
What happens when you consume too much protein?
High cholesterol and heart disease
Possible bone loss- high protein diets may cause excess CA excretion
Kidney disease
Are protein powders useful?
Not really, working the muscle promotes growth, not protein supplements
-also puts an excess load on your kidneys
Are single amino acid supplements useful?
No benefit and could lead to a deficiency in other amino acids.
- Overloads carrier proteins
- Can be toxic
