Chapter 6 - Proteins

Question 1

protein

Answer 1

“of primary importance”

- large, organic, nitrogen-containing molecules that provide the physical foundations of life

Question 2

what is chemically unique about proteins?

Answer 2

They all contain nitrogen (amino group) and a carbon, hydrogen, and oxygen (carboxyl acid group). They differ in the R group they have.

Question 3

what is structurally unique about proteins?

Answer 3

Comprised of amino acids

• nitrogen group (amine)
• acid group (carboxyl)
• hydrogen
• side chain (R-group) - determines protein name

Primary - long chain of amino acids
Secondary - bending & folding
Tertiary - assembly into 3D sheets or fibers
Quaternary - linking together of subunits (hemoglobin, collagen, silk, insulin)

Question 4

what do proteins do?

Answer 4

1. structure
2. movement
3. determine cell structure
4. membrane proteins
5. defense & repair
6. enzymes

Question 5

what makes proteins unique compared to fats & carbohydrates?

Answer 5

the body uses amino acids to build the proteins it needs

Question 6

Important task: structure

Answer 6

structural elements: bones, ligaments, tendons, hair, fur, feathers, nails, claws, hooves, beaks, protective armor, & antlers

Question 7

Important task: energy

Answer 7

muscle contraction

Question 8

Important task: cell structure

Answer 8

• cytoskeletal proteins: fibers, microtubules

- repair

Question 9

Important task: membrane proteins

Answer 9

• cell to cell communication
• allow substances to enter & leave cell - channels & receptors
• adhesion molecules
• cellular identity

Question 10

Important task: defense & repair

Answer 10

• antibodies
• extracellular matrix proteins - wound healing & immune function
• blood clotting

Question 11

Important task: enzymes

Answer 11

• perform highly specific tasks
• every reaction requires a specific enzyme
• are recycled & can be used again

Question 12

why are enzymes important proteins for living organisms?

Answer 12

• the body must carry out many reactions w/in narrow parameters of temp & pH
• enzymes lower the energy needed for reactions to happen & allow reactions w/in parameters

Question 13

how do enzymes work?

Answer 13

• they trigger a reactions - can build up (anabolic) or break down (catabolic)
• enzyme remains unchanged
• specific enzymes create specific reactions

Question 14

How can protein perform so many different tasks?

Answer 14

• amino acids are the building blocks of proteins

- they have many different ways of combining

Question 15

what are amino acids?

Answer 15

they all have the same ingredients, but take on different shape

• basic structure: amine group (NH2) + carboxyl group + R group
• R group determines protein name

Question 16

what are essential amino acids?

Answer 16

• amino acids the body needs but cannot make

- must get them from food

Question 17

nonessential amino acid?

Answer 17

ones the body needs but can make

Question 18

conditionally essential amino acids

Answer 18

essential during infancy, disease or trauma

Question 19

proteins can be a source of energy. how?

Question 20

amino acid pool

Answer 20

• supply of amino acids from food or body proteins that collect in cells and circulating blood.
• they stand ready to be used in protein & other compounds or used for energy (after nitrogen is stripped off)

Question 21

nitrogen balance

Answer 21

amount of N consumed as compared with the amount of N excreted in a given period

Question 22

negative nitrogen balance

Answer 22

• people who are starving or suffering stresses like burns, infections
• their nitrogen excretion exceed their nitrogen intake
• body is breaking down muscle & other body proteins for energy

Question 23

positive nitrogen balance

Answer 23

• growing infants, children, adolescents, pregnant women, recovering
• intake exceeds excretion
• they are retaining protein in new tissues as they grow

Question 24

amino acids - fat?

Answer 24

amino acids can be converted to fat when energy & protein intakes exceed needs & carbohydrate intake is enough.
- protein rich foods can contribute to weight gain

Question 25

deaminating acids

Answer 25

- stripping an amino acid of its Nitrogen-containing amino group (NH2) - 2 products: ammonia (NH3) & keto acid

Question 26

transamination

Answer 26

- transfer of an amino group from one amino acid to a keto acid. - produces a new nonessential amino acid & a new kept acid

Question 27

complete protein

Answer 27

- contains adequate amounts of all essential amino acids | - animal proteins - except gelatin

Question 28

urea

Answer 28

body's vehicle for excreting unused nitrogen

Question 29

incomplete proteins

Answer 29

- inadequate amounts of essential amino acids | - plant proteins - except soy

Question 30

complementary proteins

Answer 30

- combining plant proteins to compensate for limiting amino acids - two or more dietary preens whose amino acid assortments complement each other in such a way that the essential amino acids missing from one are supplied by the other

Question 31

what is a limiting amino acid? | why is it important?

Answer 31

- whatever essential amino acid is in limited supply | - body can only synthesize as much protein as there is the limiting amino acid

Question 32

protein structure

Answer 32

1. primary - sequence of amino acids 2. secondary structure - bending, twisting, folding 3. tertiary structure - determines function (3D) 4. quaternary - linking together different subunits, each of which are individual proteins (4 units make hemoglobin)

Question 33

protein quality

Answer 33

depends on: 1. digestibility 2. amino acid composition 3. reference protein 4. high-quality proteins

Question 34

protein digestibility

Answer 34

- a measure of the amount of amino acids absorbed from a given protein intake - animal proteins = high (90-99%) - plant proteins are less (70-90%, but > 90% for soy & legumes

Question 35

high-quality proteins

Answer 35

dietary proteins containing all the essential amino acids in relatively the same amounts humans need; may also contain nonessential amino acids

Question 36

reference proteins

Answer 36

- a standard agains which to measure the quality of other proteins - compared to what a preschooler needs

Question 37

what diseases do protein deficiency cause?

Answer 37

protein-energy malnutrition - kwashiokor - acute malnutrition - body becomes swollen with edema - marasmus - - chronic malnutrition - body wastes away

Question 38

Evaluating proteins: | NPU

Answer 38

Net Protein Utilization - ratio of amino acids converted to protein/amino acids supplied Experimentally - determine protein intake & measure nitrogen excretion - range can be 0 - 1 (1 being a good balance of amino acids needed to those supplied)

Question 39

Evaluating proteins: | BV

Answer 39

Biological Value - measures proportion of absorbed protein that becomes body protein - uses measure of urinary & fecal nitrogen

Question 40

Evaluating proteins: | PDCAAS

Answer 40

Protein Digestibility-corrected amino acid score | - compares the amino acid composition of a protein w/human amino acid requirements and corrects for digestibility

Question 41

Evaluating proteins: | PER

Answer 41

``` Protein Efficiency Ratio weight gain (g) / test protein intake (g) - measures weight gain of growing animal & compares it to the animal's protein intake ```

Question 42

How is protein digested?

Answer 42

starts in the STOMACH - HCl uncoils (denatures) each protein's tangled strands so digestive enzymes can attack the peptide bonds. HCl activates pepsinogen to active form: PEPSIN - which cleaves large polypeptides into smaller polypeptides & some amino acids SMALL INTESTINE - pancreatic & intestinal PROTEASES further break them down into short peptide chains, tri-, di-peptides, & amino acids. Then PEPTIDASE enzymes on membrane surface of intestinal cells split them into amino acids

Question 43

Protein absorption

Answer 43

- done in small intestine - specific carriers transport amino acids into intestinal cells - may be used for energy or to synthesize needed compounds - amino acids not used are transported across the cell membrane & then enter capillaries (on their way to the liver)

Question 44

What is adequate protein intake?

Answer 44

RDA recommendations = 0.8 g/kg of body weight | 10-35% of energy intake

Question 45

How to make sure you have an adequate intake of protein?

Answer 45

- use several unrefined sources of fats & carbs (fruits, veggies, nuts, seeds, beans, & grains) - vary diet - add reasonable lean animal protein

Question 46

functions of proteins

Answer 46

1. produce vial body structures 2. maintain fluid balance (plama proteins) - edema 3. contributes to acid-base balance 4. forms hormones, enzymes & neurotransmitters 5. immune function - (anergy = immune incompetence) 6. transport nutrients 7. forms glucose (gluco neogenesis & cachexia (muscle wasting)) 8. provides energy (4 kcal/gm)

Question 47

Health concerns: | Protein deficiency

Answer 47

kwashiorkor | marasmus

Question 48

Health concerns: | Too much protein

Answer 48

Heart disease Cancer Adult Bone Loss (osteoporosis) - when protein is high, calcium excretion increases; calcium to protein ratio should be 20-1 Kidney disease

Question 49

Why is protein an inefficient energy source?

Answer 49

the liver can break down amino acids to make glucose (gluconeogenesis), but not much is made & tissue protein is sacrificed.

Question 50

What are some important considerations if you are a vegetarian?

Answer 50

- plant proteins are lower quality than animal proteins - plants also offer less protein - improve quality of proteins by combining foods that have different, but complementary amino acids - eat a variety of whole grains, legumes, seeds, nuts, & vegetables