Proteins and Amino acids Flashcards
Describe the structural characteristics of proteins.
- Differentiated from carbohydrates and fats with the addition of nitrogen (as well as carbon hydrogen and oxygen)
- Amino acids are the basic building blocks of proteins BUT not all amino acids are protein building blocks. There are hundreds of non-protein amino acids that have other uses.
- Each amino acid contains
1. An amino group
2. A corboxylic group
3. A unique side group R which differentiates amino acids - Whilst there approximately 1000 amino acids in nature? The human body only uses 20?
- The amino acid chain is the primary structure and folds in a certain pattern to create 3-D structure which is closely linked to the function of the protein
Name the 9 essential amino acids
Clue: PVT TIM HiLL
Which of the essential amino acids is contentious and why?
Histidine
- it is synthesised in children but in adults whilst intestinal bacteria can produce histadine, it is not clear how much is provided.
- It is the only Amino acid that does not appear to impair protein synthesis when it is deficient in the diet so that seems to make it nonessential in nature.
List the main functions of protein
Growth and Maintenance
Hormones and receptors
Enzymes
Immunoglobulins (or antibodies)
Transport
Buffers
Fluid balance
Multiple functions of glycoproteins
How are proteins involved in the bodies growth and maintenance?
Proteins are the building blocks of muscles, blood, skin and most body structure.
- BONES are formed of collagen matrix (made up of amino acid) which provides a framework for minerals to deposit on.
- Ligaments, tendons, blood vessel walls, skin all use collagen as a building material
- ACTIN and MYOSIN filaments involved in muscle contractions are also protein
- Proteins are also needed for the replacement of cells. For example in the skin and the gastrointestinal tract cells are replaced every 4 to 5 days.
How are proteins involved with hormones and receptors?
Give 4 examples
Some hormones are derived from cholesterol such as reproductive hormones, cortisol, glucocorticoids for example.
Others are made from
Amino acids.
Tyrosine + Iodine»_space;> thyroid hormones
Tyrosine.»_space;> needed for the neurotransmitters dopamine, norepinephrine, epinephrine
Tryptophan»_space;> needed for the hormones/ neurotransmitters serotonin and melatonin
two polypeptide chains - insulin
one polypeptide chain - glucagon, PTH, calcitonin
Cell membrane proteins are receptors for hormones
How are proteins involved in the immune system?
Immunoglobulins are proteins found in blood and body fluids and are used by the immune system to identify and neutralise foreign materials such as bacterial viruses.
We have IgG, IgA, IgM and IgE
How is protein involved in transport systems in the body?
Give 4 examples
Some proteins act like a taxi service combining with other substances in the blood or within cells to provide a mode of transport. Without these proteins, we would not be able to deliver vital nutrients..
Eg:
Albumin - the most predominant protein in blood which can bind to calcium, zinc and B6 as well as steroids and fatty acids
Transferrins which bind to iron
ceruloplasmin which binds to copper
Haemoglobin which transports oxygen in the blood
How is protein involved in buffers?
Name 2 amino acids that buffer
This is to do with maintaining a pH of 7.35 to 7.45 in the blood. There are many mechanisms to help this and one of these are certain amino acids that have sidechain (R groups) that can easily pick up or let go of hydrogen ions thus helping to regulate acid balance in body fluids.
Proteins that have a lot of of these types of amino acids make good buffers.
Histadine is the best buffer .
Cysteine is also a buffer
What are some examples of glycoproteins?
Proteins bound to a sugar/carbohydrates,
Eg:
Mucins: found in mucus and saliva and provide protection and lubrication.
ABO blood type antigens - determines what blood group we are
Hormones: LH, FSH, T-SHIRT
Major Histocompatibility complex
proteoglycans shock absorbers that draw in fluid and keep it hydrated.
What is deamination in terms of protein metabolism?
Why does it happen?
Deamination is the removal of the nitrogen containing amino group from amino acids.
This is necessary for protein to be stored as fat or used as energy. When the protein drops nitrogen what’s left are amino acid fragments that can be used to produce glucose or ketones?
What is the byproduct of deamination and how are its potentially dangerous effects dealt with?
When the nitrogen group is removed from the amino acid, ammonia is formed which is very toxic.
It is the urea cycle that ensures it is excreted. Ammonia is converted to water soluble compounds so that it can be excreted as part of urine by the kidneys.
The Urea cycle takes place in the liver. if the liver is not functioning well it affects the urea cycle which can lead to a buildup of ammonia – hyper ammoniaemia.
Another benefit of the urea cycle is the that it is the sole endogenous source of amino acids arginine and citrulline, plus ornithine which is an important liver support and detox agent .
What is transamination?
It is very important in the synthesis of some non-essential amino acids .
When one non-essential amino acid is in good supply and another is low but in demand it is helped out by the one that is in good supply.
The amino group of an amino acid is transferred onto an enzyme. The enzyme then transfers the amino group onto a keto acid, thus forming a new amino acid.
It is a homeostatic mechanism
What is the co-factor transamination requires for a reaction to occur?
Where do we find it?
B6
Whole grains, green vegetables, sunflower seeds, pistachios, walnuts, bananas, lentils, avocados, meat and fish
What do we mean by the amino acid pool?
Why is it important to have a regular supply of protein?
- Amino acids freed from proteins when the proteins break down + amino acids from diet derived sources?
- Amino acid are utilised or excreted. They are not stored.
Essential amino acids generally have a longer half life than non-essential.
