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Human Nutrition > Chapter 6 - Proteins > Flashcards

Chapter 6 - Proteins Flashcards

1
Q

protein

A

“of primary importance”

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

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2
Q

what is chemically unique about proteins?

A

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

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3
Q

what is structurally unique about proteins?

A

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)

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4
Q

what do proteins do?

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

what makes proteins unique compared to fats & carbohydrates?

A

the body uses amino acids to build the proteins it needs

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6
Q

Important task: structure

A

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

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7
Q

Important task: energy

A

muscle contraction

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8
Q

Important task: cell structure

A
  • cytoskeletal proteins: fibers, microtubules

- repair

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9
Q

Important task: membrane proteins

A
  • cell to cell communication
  • allow substances to enter & leave cell - channels & receptors
  • adhesion molecules
  • cellular identity
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10
Q

Important task: defense & repair

A
  • antibodies
  • extracellular matrix proteins - wound healing & immune function
  • blood clotting
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11
Q

Important task: enzymes

A
  • perform highly specific tasks
  • every reaction requires a specific enzyme
  • are recycled & can be used again
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12
Q

why are enzymes important proteins for living organisms?

A
  • 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
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13
Q

how do enzymes work?

A
  • they trigger a reactions - can build up (anabolic) or break down (catabolic)
  • enzyme remains unchanged
  • specific enzymes create specific reactions
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14
Q

How can protein perform so many different tasks?

A
  • amino acids are the building blocks of proteins

- they have many different ways of combining

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15
Q

what are amino acids?

A

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
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16
Q

what are essential amino acids?

A
  • amino acids the body needs but cannot make

- must get them from food

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17
Q

nonessential amino acid?

A

ones the body needs but can make

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18
Q

conditionally essential amino acids

A

essential during infancy, disease or trauma

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19
Q

proteins can be a source of energy. how?

A
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20
Q

amino acid pool

A
  • 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)
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21
Q

nitrogen balance

A

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

22
Q

negative nitrogen balance

A
  • 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
23
Q

positive nitrogen balance

A
  • growing infants, children, adolescents, pregnant women, recovering
  • intake exceeds excretion
  • they are retaining protein in new tissues as they grow
24
Q

amino acids - fat?

A

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

25
Q

deaminating acids

A
  • stripping an amino acid of its Nitrogen-containing amino group (NH2)
  • 2 products: ammonia (NH3) & keto acid
26
Q

transamination

A
  • transfer of an amino group from one amino acid to a keto acid.
  • produces a new nonessential amino acid & a new kept acid
27
Q

complete protein

A
  • contains adequate amounts of all essential amino acids

- animal proteins - except gelatin

28
Q

urea

A

body’s vehicle for excreting unused nitrogen

29
Q

incomplete proteins

A
  • inadequate amounts of essential amino acids

- plant proteins - except soy

30
Q

complementary proteins

A
  • 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
31
Q

what is a limiting amino acid?

why is it important?

A
  • whatever essential amino acid is in limited supply

- body can only synthesize as much protein as there is the limiting amino acid

32
Q

protein structure

A
  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)
33
Q

protein quality

A

depends on:

  1. digestibility
  2. amino acid composition
  3. reference protein
  4. high-quality proteins
34
Q

protein digestibility

A
  • 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
35
Q

high-quality proteins

A

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

36
Q

reference proteins

A
  • a standard agains which to measure the quality of other proteins
  • compared to what a preschooler needs
37
Q

what diseases do protein deficiency cause?

A

protein-energy malnutrition

  • kwashiokor - acute malnutrition - body becomes swollen with edema
  • marasmus - - chronic malnutrition - body wastes away
38
Q

Evaluating proteins:

NPU

A

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)

39
Q

Evaluating proteins:

BV

A

Biological Value

  • measures proportion of absorbed protein that becomes body protein
  • uses measure of urinary & fecal nitrogen
40
Q

Evaluating proteins:

PDCAAS

A

Protein Digestibility-corrected amino acid score

- compares the amino acid composition of a protein w/human amino acid requirements and corrects for digestibility

41
Q

Evaluating proteins:

PER

A 
Protein Efficiency Ratio
weight gain (g) / test protein intake (g)
- measures weight gain of growing animal & compares it to the animal's protein intake
42
Q

How is protein digested?

A

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

43
Q

Protein absorption

A
  • 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)
44
Q

What is adequate protein intake?

A

RDA recommendations = 0.8 g/kg of body weight

10-35% of energy intake

45
Q

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

A
  • use several unrefined sources of fats & carbs (fruits, veggies, nuts, seeds, beans, & grains)
  • vary diet
  • add reasonable lean animal protein
46
Q

functions of proteins

A
  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)
47
Q

Health concerns:

Protein deficiency

A

kwashiorkor

marasmus

48
Q

Health concerns:

Too much protein

A

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

49
Q

Why is protein an inefficient energy source?

A

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

50
Q

What are some important considerations if you are a vegetarian?

A
  • 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

Human Nutrition (8 decks)

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