Proteins Flashcards
How does the chemical structure of proteins differ from the structures of carbohydrates and fats?
- Proteins contain an amino group (NH2). Compared to carbohydrates only containing C,H,O molecules and fats containing a glycerol.
Describe the structure of amino acids and explain how their sequence in proteins affects the proteins shapes. What are essential amino acids?
- Amino acids contain C, H, O, N
- Sequence effects their functionality of the protein. (DNA sequences are unique. Change in nucleotide sequence may lead to different A.A added to chains. Therefore, function different
- E.A.A need to consume via diet as they cannot be synthesized.
o Are synthesized in small amounts but not sufficient.
Describe protein digestion
DIGESTION:
- Stomach: Proteins -> Smaller Polypeptides
o HCL uncoils protein strands and activates Pepsin.
HCL denatures structure.
Pepsin is activated by Pepsinogen.
o Pepsin: Cleaves protein into smaller polypeptides and some free amino acids.
Pepsin inhibits pepsinogen synthesis.
- Small Intestine & Pancreas: Polypeptides -> Tri/Di/Peptides -> Amino Acids
o Pancreatic and small intestine enzymes split polypeptides further.
Enzymes on surface of the small intestinal cells hydrolyze peptides and the cells absorb them.
Describe protein absorption
- ABSORPTION: all protein is absorbed as tripeptides, dipeptides or amino acids and this process occurs in the duodenum or proximal jejunum of the small intestine. The peptides and/or amino acids pass through the interstitial brush border by facilitative diffusion or active transport.
- Occurs in small intestine. Where specific carriers transport amino acids into intestinal cells.
o Undergo two fates:
Used for energy via gluconeogenesis. (Broken down)
Used in synthesis of needed compounds.
o A.A that aren’t used are transported across cell membranes into surrounding fluids where they enter the capillaries o their way into the liver.
Describe protein synthesis:
- Protein synthesis is the building (anabolic) reaction of amino acids condensing together to create larger proteins within the body.
o Condensation reaction – Amino acids joining together.
Amino acids joining to give off water.
What are the roles of protein in the human body?
- Synthesis:
o Cells synthesis proteins according to genetic information provided by the DNA of each cell. - Roles of proteins
o Building materials for growth and maintenance.
o As enzymes
o As hormones (insulin/glucagon)
o Regulators of fluid balance
o Blood Plasma (Intracellular and extracellular)
o Acid base regulators
o Transporters (Haemoglobin, lipoproteins)
o Antibodies
o Energy source.
What are enzymes? What role does enzymes play in chemical reactions?
- Enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place within cells (LOWER ACTIVATON ENERGY) They are vital for life and serve a wide range of important functions in the body, such as aiding in digestion and metabolism
How does the body use amino acids
- Used in synthesis.
- Used for energy.
What is deamination
- Deamination is the removal of the amino (NH2) group from an amino acid.
Define Nitrogen Balance, what conditions are associated with zero, positive and negative balances?
- A measure of nitrogen input minus nitrogen output.
o Positive – Persons in growth. (Children, muscle growth)
o Zero – Maintaining bodyweight.
o Negative – Muscle wasting. (Sickness, malnourishment, HIV ETC)
What factors affect the quality of dietary protein?
- Digestibility, essential amino acids, and limiting amino acid composition for nonruminants
- The two most limiting amino acids are lysine and methionine.
What is high quality protein?
- Sources of food that contain complete proteins. (essential and non-essential amino acids)
o Meats, Eggs, Milks, etc.
How can vegetarians meet their protein needs without eating meat?
- By combining the consumption of non-essential proteins with complimentary proteins in meals to ensure full spectrum of amino acids.
o Examples:
Lentils or legumes with grains, nuts/seeds or dairy
Grain foods with dairy products
Dairy with nuts and/or seeds
What are health consequences of ingesting inadequate protein and energy? Describe marasmus and kwashiorkor’s disease. How can they be distinguished and in what ways do they overlap.
- PEM – Protein Energy Malnutrition is a condition where human body wastes away.
o Prone to infections and impaired growth. - In western society is common with HIV/AIDs and renal failure.
- Undeveloped nations is common with children.
o Presents as:
o Marasmus (Dying away): Severe energy and protein deficient. (Slow)
Occurs in children aged 6 -18 months normally.
Impaired brain development.
Stops growing.
o Kwashiorkor’s: Moderate energy deficit with severe protein deficiency. (Rapid)
• Generally occurs when 2nd child is born. 1st child has sudden diet switch to low quality food.
Comes to light with infections. (Impaired immune system.)
Limbs & abdomen becomes swollen with odema.
How might protein excess or type of protein eaten, influence health?
- Heart Disease (Saturated fat content)
- Cancers (Related to sat-fat intake and bowel.)
- Adult bone loss (Osteoporosis) – High protein intake increases calcium excretion.
- Weight loss through satiety.
- Kidney disease through urea cycle.
What factors are considering in establishing recommended protein intakes?
- 0.84g/kg for males.
- 0.75g/kg for females.
o More during growth, pregnancy and elderly (70+) - 10 – 35% of intake.
What are the benefits and risks of taking protein and amino acid supplements?
- Spares muscle wasting in dieters and athletes.
- Not needed in normally/healthy people.
- Used with fighting sarcopenia (Muscle wasting in very old and frail)
o Associated with anorexia, immobility and ill health.
Which part of its chemical structure diffenentiates one amino acid from another?
- Its side group (-R)
Isoleucine, leucine and lysine are?
- E.A.A
In the stomach, hydrochloric acid does:
- Denatures protein (Uncoils) and activates pepsin
Proteins that facilitate chemical reactions are?
- Enzymes
If an essential amino acid that is needed to make a protein is unavailable, the cells must:
- Breakdown proteins to obtain it
Protein turnover describes the amount of protein:
- Synthesised and degraded.
Marasmus develops from
- Inadequate protein and energy intake.
The RDI for a healthy male and female is:
- M – 0.84g/KG
- F – 0.75g/KG.
