Chapter 6 Flashcards
(35 cards)
What are proteins?
How are they constructed
Energy-yielding nutrients & are chemically similar to carbs and lipids.
A chain of amino acids linked together by peptide bonds (covalent bonds). Long chain of amino acids is a polypeptides → once completed, its a protein
What are the three parts of the amino acid?
(1) Amino Group: Contains a Nitrogen Atom; identical with all amino acids
(2) Acid Group: Identical with all amino acids
(3) Side Group (Function Group): Unique for each of the 20 amino acids
How is a protein shape determined?
How can the shape be broken?
Determined by the sequence of amino acids along the chain
Changes to the environment of a protein may break apart hydrogen bonds causing the protein to unfold (unfold = non functional)
What causes a protein to denature?
Change in temperature or pH
In food: changes texture/ consistency; in body: simply non functional
Give three examples of denatured proteins in the kitchen
(1) Effects of pH on Protein: Adding lemon juice (acidic) to milk (solution of fat, proteins, and water). Drop in pH causes the casing protein to fall apart → become curdles (not gone bad)
(2) Effects of Temperature on Protein: Slow cooking of eggs (with whisking) causes the egg white and yolk to denature → creamy eggs
(3) Effects of Whipping on Protein: Forming a meringue is a mechanical denaturing of proteins
What does slow-cooking do?
Denatures muscle proteins. Muscle fibres arranged in bundles held by collagen. When meat is slow-cooked, collagen denatures → reduces toughness of meat
What are the protein functions?
(1) Provide Structural Support and Movement
(2) Work as enzymes
(3) Work as hormones
(4) Maintain fluid balance
(5) Regulate pH of fluids
(6) Crucial components of cell membranes
(7) Source of energy
(8) Antibodies are Proteins
What are the protein functions?
What is meant by “Provide Structural Support and Movement”
(3 examples)
- Collagen fibres are the foundation of bone
- Muscle tissue is almost exclusively protein
- Keratin is a protein that makes up nails, skin, hair
What are the protein functions?
What is meant by “Work as enzymes”?
(3 examples)
- Enzymes are proteins
- They work to digest food in the mouth, stomach, and small intestine
- Must be properly folded to digest food
What are the protein functions?
What is meant by “Work as hormones”?
(2 examples)
- Some hormones are proteins
- Insulin (taken as injections, if oral → stomach acids would denature it)
What are the protein functions?
What is meant by “Maintain fluid balance”?
(3 examples)
- Plasma proteins are necessary for maintaining fluid levels within tissues
- They hydrogen bond with water, preventing it from leaking out of the blood capillaries
- Lack of proteins can cause edema (swollen tissue)
What are the protein functions?
What is meant by “Crucial components of cell membranes”?
(2 examples)
- Lipid bilayer is studded with protein
- They function as channels/ pumps for substances to go into or out of the cell
What are protein functions?
What is meant by “Antibodies are Proteins”
(1 example)
- Antibodies bind to pathogens (bacteria) and flag them for destruction
What is protein synthesis?
Eat proteins → digestion → break down into amino acids → amino acids are absorbed and delivered to the cells of the body → cells have required material to build specific proteins
What are the steps required to make a protein?
(1) Gene is copied onto mRNA
(2) mRNA leaves the nucleus and binds to a ribosome (machine that builds the protein)
(3) mRNA molecule is read and different amino acids are fished out the cell by tRNA and brought to the growing polypeptide chain
(4) polypeptide chain is completed and released and folds into a 3D shape to make a protein
What happens if the body is missing some amino acids?
Protein synthesis halts. The partially made polypeptide chain is dismantled and its amino acids are returned to the pool.
What is the protein digestion process in the stomatch?
(1) Hydrochloric acid (HCl/ H-C-L) denatures food proteins in stomach
(2) HCl activates pepsin (stomach enzyme that cuts denatured proteins into smaller polypeptides)
What is the protein digestion process in the small intestine?
(1) Pancreas secretes more protein-splitting enzymes. Breaks polypeptides into shorter peptides and amino acids
(2) Amino acids are the end products of protein digestion
What happens after protein digestion?
Amino acids enter the hepatic portal vein. First go to the liver, then to the rest of the body. Liver keeps some amino acids for its needs and releases the rest into general circulation.
What is protein turnover?
Recycling of protein. Body breaks down proteins into amino acids to then build new proteins.
What is hemoglobin?
Protein found inside red blood cells. They deliver oxygen to the cells of the body
What is nitrogen balance?
Protein is 16% nitrogen. Nitrogen is crucial for synthesis of many compounds in the body. We need a constant amount of Nitrogen in our bodies
Define Nitrogen Equilibrium
Intake + Retention = Losses
(1) Intake: Food from (dietary proteins)
(2) Retention: Protein turnover (recycling amino acids)
(3) Losses: Nitrogen losses in urine (from break down of amino acids), feces, and sweat
What are the possible outcomes from nitrogen equilibrium?
(1) Positive Nitrogen Intake: happens during pregnancy, lactation, resistance exercise, recovery from illness, growing children.
(2) Negative Nitrogen Balance: Happens during starvation, emotional trauma and other traumas. Leads to breaking down of muscle protein and other body protein
