Midterm #2 Flashcards
What determines protein structure?
the sequence of amino acids
What determines protein function?
Its shape, determined by primary/secondary/etc. structure
What is a protein?
one or more polypeptide chains folded into a three dimensional shape
Describe the connection between form and function for collagen/connective tissue proteins.
elongated, used to for structural benefits
How can you denature a protein?
change in pH, heat, etc.
What is transamination?
Can be used in synthesis of nonessential amino acids; transferring an amino group from one AA to another compound to create a new AA
What are essential amino acids?
AAs that the body can’t make at all/enough of, so we need to supply in diet
What are the four components of an amino acid?
H, amino, carboxyl (acid), R-side chain
What are the building blocks of protein?
Amino acids
Why is fever so dangerous?
High body temperature shuts down enzyme systems due to protein denaturation effects
What nutrients are in animal protein sources?
some B vitamins, and minerals (iron, zinc, calcium); BUT low in fiber and potentially high in fat)
What nutrients are in plant protein sources
B vitamins, minerals (iron, zinc, calcium); BUT in less absorbable forms
When protein is absorbed in the small intestine, what gets passed through to the blood?
ONLY amino acids, no peptides!
How are proteins related to food allergies?
Allergy when we absorb the protein whole instead of broken into amino acids
Describe the relationship between Americans and proteins.
Deficiency is rare, and 2/3 of dietary protein comes from animal sources
Describe the relationship between the rest of the world and proteins.
Vegans do get enough, and most of the world gets dietary protein from plant sources (grains and vegetables)
Describe the relationship between economic status and protein sources
The higher the economic status, the more animal protein you have available to eat
How can you use diet to reduce risk of heart disease?
Plant-based diets: phytonutrients
What food increases risk of heart disease?
Not saturated fat in general, but from red meats (dairy fat and eggs are okay)
What is the effect of PUFAs on heart disease?
Increase lipid oxidation and increase risk
What is the main source of PUFAs?
vegetable seed oils and red meats
What are reduced fat foods?
when fat is removed, replaced, or is a form that cannot be absorbed
Give some examples of reduced-fat foods
Nonfat/skim milk (removed), carb/protein/fat replacements (Olestra = sucrose polyester)
What can you make from the amino acid pool in the body?
energy, glucose or FAs, nitrogen-containing compounds, other amino acids
What are the two steps to protein synthesis?
transcription and translation
What happens at the end of protein digestion?
Nitrogen made into urea and excreted
Is using % dietary lipid for recommendations supported by the research literature?
no
What kind of nutrient reduces the risk of heart disease?
phytonutrients: plant based diet
What kinds of animal foods are related to heart disease risk?
Red meat; not dairy fat, not eggs
What is the main cause of red meat’s contribution to heart disease risk?
PUFAs: some vegetable seed oils, but mostly in red meats; increases lipid oxidation
What is the effect of reduced fat foods?
Doesn’t have same satiety effects of fat; doesn’t really show benefits for weight control
What are some ways of making reduced fat foods?
Remove, replace, or put in undigestable/unabsorbable fats instead (non-fat and skim milk; replacement with a carb; sucrose polyester Olestra, etc.)
What nutrients are supplied by animal and plant protein foods?
Animal (B vitamins and minerals, low fiber), Plant (B vitamins, fiber)
What is the relationship between shape and function of protein?
Shape determines function: hemoglobin, connective tissue, etc.
How can you denature proteins?
change in pH, heat, agitation, etc.
What part/form of protein passes from the intestinal lumen to the blood stream?
Amino acids
What is a food allergy?
absorbing the protein whole and causing an immune response
What are some protein functions?
enzymes, transport proteins, antibodies, contractile, some hormones, regulating fluid balance and acid-base balanec
Name two protein deficiencies
Kwashiorkor and Marasmus
What is Kwashiorkor?
protein-only deficiency; have enough energy but no protein, and immune system functions
What is marasmus?
Protein and energy deficiency; wasting, like in AIDS and cancer
How to make trans FAs?
hydrogenation: add hydrogens to unsat FAs; double bonds become saturated
What are the health issues of trans fats?
increase risk of heart disease and cancer
Where can you find trans fats?
in foods with long shelf life
What are phospholipids?
TGA with phosphate group (2 FAs, one phosphate on the glycerol)
What is the function of phospholipids?
emulsifiers (allow suspension of fat in water; forms micelles; detergent) and lipid bilayer
What are sterols?
lipid found in plants and animals; doesn’t dissolve in water welll; cholesterol
What is cholesterol?
sterol found only in animal foods; more than 90% of our cholesterol is in our cell membranes
what do we need to emulsify lipids?
bile
Where is bile stored?
gallbladder
what are lipases?
enzymes that remove FAs from TGs
what are two kinds of lipase?
Gastric: in stomach, but minimal digestion of lipids there; Pancreatic: digests TG into monoglyceride and 2 free FAs
What are lipoproteins?
proteins that carry water-insoluble lipids (TG, cholesterol), phospholipids;; can also transport fat-soluble nutrients; complex of the lipid and protein
What does the protein part of the lipoprotein do?
gives the lipid a charge to allow it to stay in fluid
What are four types of lipoproteins?
chylomicrons, VLDL, LDL, HLDL
what are chylomicrons?
lipoprotein; transports long chain FAs into lymphatic system; delivers TGs to body’s cells (carries diet-derived lipids: TGs, cholesterol, phopshoplipids, etc.; made in intestinal tract)
What do chylomicrons carry?
mostly diet-derived lipids; TGs, cholesterol, phospholipids, (mostly TG but can carry cholesterol)
What are VLDLs?
produced from the liber; takes extra energy from carbs (glucose) and protein (AAs) and catabolize to 2C acid for FA anabolism; VLDLs carry this fat from liver to body cells
What does fasting TGs mean?
what you measure with blood test in fasting state; NOT the chylomicrons
What is LPL?
lipoprotein lipase: removes TG from VLDL and creates IDL (intermediate density LP)
What are LDLs?
1/3 of IDL have additional TG removed and become LDLs: main carrier of blood cholesterol (if high blood cholesterol, often have high LDL); cells have LDL receptors to bring cholesterol into cell
What does it mean to have elevated LDL?
most likely due to genetic effect in LDL receptor; can’t get it out of system; receptors mainly on liver; elevated oxidized LDLs increase risk for heart siease
what are HDLs?
bring cholesterol back to liber, help decrease LDL oxidation; primarily genetically determined
What is the relationship between blood TG and HDL levels?
inverse
Can you increase HDLs with exercise?
not really; and can’t change more than 10% at all
What is the relationship between HDL and heart disease risk?
positive! HDLs are good
What is the function of stored lipid?
stored energy as TGs in adipose tissue; insulation; protection/cushioning
What is the function of cholesterol?
used to make some hormones (sex hormones, cortisol); Vitamin D; bile; component of cell membranes, only in animal foods!
What is the function of PUFAs?
essential; growth, skin integrity, fertility, structure and function of cell membranes; omega-3 and -6
What do Omega3/6 FAs do?
make eicosanoids (competition at first enzyme); hormone-like (act where synthesized)
What do omega-3 do?
decrease inflammation, clotting, BP
What do omega-6 do?
increase inflammation, clotting, BP
what are the health benefits of omega3?
we’re inefficient at converting 18C to 20C, which we need; therefore we can’t get benefit from plant products; have to get from fish: better for heart disease risk than Omega6
what happens with an excess of oxidation from too many PUFA?
oxidation of DNA (cancer); LDL (atherosclerosis), and cell membranes
Are plant sources good sources of Omega-3/6?
No: they only have the 18C version, which we cannot convert to 20/22C (which we need)
What sources of Omega3 and Omeg6 are 20c vs 22c?
EPA (fish oil) and arachidonic (red meat) are 20c /// DHA (fish oil) is 22c
How do we get energy from TGs?
Beta-oxidation: breaking up the FAs in groups of 2C (acetyl-CoA)
What happens to lipid metabolism during feasting?
excess energy stored in liver as TGs (in adipose cells)
Where is excess lipid energy stored, and in what form?
In adipose cells of the liver; as TGs
How is excess lipid energy stored in the liver? (process)
LPL breaks fats into TG and stores in adipose tissue
What happens to lipid metabolism during fasting?
TGs from adipose tissue are broken down and released for energy bia HSL
What is HSL?
hormone sensitive lipase: breaks down TGs from adipose cells for energy during fasting; releases fat into the blood