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FNH 250 > Proteins > Flashcards

Proteins Flashcards

1
Q

How are proteins stored?

A

We do not store excess protein, but small amino acid will pool in cells.

– all are in use, in either functional or structural roles

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2
Q

What are structural functions of proteins?

A
  • tendons,ligaments
  • scar tissue
  • hair, nail protein
  • PRO matrix of bone
  • skin
  • muscle
  • new tissue, etc.
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3
Q

What are the functional functions of proteins?

A
  • enzymes
  • immune bodies
  • hormones
  • cellular pumps, channels
  • blood transport PRO
  • muscle
  • blood clotting PRO, etc.
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4
Q

How much energy does protein provide?

A
  • minor source of energy
  • provide 4 kcal/g
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5
Q

What are protein monomers?

A
  • in contrast to CHO polysaccharides (repeating units of same molecule, GLU), proteins are repeating units of different molecules, ~20 amino acids
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6
Q

What element does protein supply to the body?

A

Protein supplies Nitrogen (N) to the body

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7
Q

Protein is a major substituent of what tissue?

A

lean tissue

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8
Q

What is the structure of an amino acid, and how do they differ?

A

Different side chains give amino acids different properties

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9
Q

What are essential amino acids?

A
  • body can’t synthesize these amino acids at all or in adequate quantities to meet body needs
  • must be obtained in diet
  • 10 for children, 9 for adults
  • when the supply of any one of the essential amino acids is depleted, protein synthesis stops (or is on hold) as the body breaks down its own proteins to supply the missing essential amino acid
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10
Q

List the essential amino acids.

A

PVT

  • Phe – phenylalanine
  • Val – valine
  • Thr – threonine

TIM

  • Trp – tryptophan
  • Ile – isoleucine
  • Met – methionine

HALL

  • His – histidine
  • Arg – arginine*
  • Leu – leucine
  • Lys – lysine

*essential for children, higher need during growth

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11
Q

List the non-essential amino acids.

A
  • Ala – alanine
  • Glu – glutamic acid
  • Asn – asparagine
  • Ser – serine
  • Asp – aspartic acid

AGASA

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12
Q

How are non-essential amino acids synthesized?

A
  • synthesized in cells via TRANSAMINATION
  • requires vitamin B-6
  • transfer of an amine group from one amino acid to a C-skeleton (keto-acid) to form a new amino acid
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13
Q

What are the semi-essential amino acids?

A
  • Arg, Cys, Gln, Gly, Pro, Tyr
  • a few non-essential amino acids are/become essential under certain conditions (e.g., infancy, critical illness)

Examples:

  • normally, Cys and Tyr are non-eaa because we can make Cys from Met (eaa) and Tyr from Phe (eaa)
  • if we don’t consume enough Met or Phe in our diets this will make Cys and Tyr conditionally (semi) essential
  • if we don’t consume the conditionally essential aa in the diet, then protein synthesis will stop and the body will turn to internal protein sources for these amino acids
  • PRO synthesis is an ‘all or none’ situation
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14
Q

Which amino acids are used to synthesize Cysteine, and which are used to synthesize Tyrosine?

A
  • Cys from Met (essential)
  • Tyr from Phe (essential)
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15
Q

How are pools of amino acids within cells formed?

A
  • each cell contains a small pool of amino acids derived from dietary intake, amino acid recycling (transamination), and internal protein breakdown
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16
Q

What is protein turnover?

A

Recycling and Deamination of Amino Acids Recycling:

  • each day more amino acids are recycled in the body than are consumed in the diet (~300 g/day recycled in body and ~100 g/day consumed)
  • recycling of amino acids in body is PROTEIN TURNOVER: the synthesis and degradation of endogenous proteins to reduce our dietary need to ingest large quantities of protein
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17
Q

How are amino acid pools inside cells used?

A
  1. used to synthesize other proteins (e.g., hormones, neurotransmitters, receptors)
  2. synthesized into non-essential amino acids via transamination
  3. recycled into vitamins (e.g.,Trpeaa niacin)
  4. DEAMINATED (loss of amino group from an amino acid) to produce N (amino group) and keto-acid (carbon skeleton that can be used for energy metabolism)
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18
Q

What is the process of amino acid deamination, and what are the products?

A
  • (loss of amino group from an amino acid) to produce N (amino group) and keto-acid (carbon skeleton that can be used for energy metabolism)
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19
Q

What can keto-acids (carbon skeletons) be used for?

A
  • burned for immediate energy
  • synthesized into FA for storage as potential energy
  • ketogenic amino acids are catabolized and the C-skeleton used to produce fat (Leu & Lys are purely ketogenic)
  • used to synthesize GLU via gluconeogenesis (in liver, certain kidney cells)
  • glucogenic amino acids are broken down and the C-skeleton used to produce GLU (includes all amino acids except Leu, Lys)
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20
Q

In deamination produces keto acis and N. What happens to the amino group?

A
  • N (amino group) processed to initially form AMMONIA (toxic)
  • liver detoxifies ammonia into UREA (non-toxic)
  • urea travels out of liver into bloodstream to be filtered by the kidneys (urea = major waste product from body)
  • body removes N by way of urea excretion in urine
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21
Q

How is urea synthesized?

A
  • urea = major waste product from body
  • body removes N by way of urea excretion in urine
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22
Q

Why is urea synthesized?

A

Urea is due to excess protein intake.

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23
Q

How is the quality of dietary protein assessed?

A
  • the quality of dietary proteins is measured by how much N is retained in the body, or by how well the protein supports growth
  • quality depends on digestibility of the protein and “completeness” of the essential amino acids in the food relative to human needs
  • different chemical and biological methods are used to determine protein quality including:

Amino Acid Score

Biological Value

Protein Digestibility Coefficient Amino Acid Score

Digestible Indispensable Amino Acid Score

Protein Efficiency Ratio

Net Protein Utilization

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24
Q

What are complete proteins?

A
  • provide all the essential amino acids in adequate quantities that support human growth, maintenance and repair
  • efficient use in body because pattern of essential amino acids provided in food closely matches pattern of essential amino acids need by humans
  • generally animal foods
  • plant sources: soy, quinoa, buckwheat, hemp, chia, amaranth, tempeh, spirulina
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25
Q

What are incomplete proteins?

A
  • at least one essential amino acid is lacking in quantity to support body growth, maintenance and/or repair
  • ‘limiting amino acid’ is the essential amino acid in lowest concentration in a food
  • cannot support growth and maintenance because once an essential amino acid is used up, protein synthesis stops until body proteins can supply the required essential amino acid in adequate amounts
  • generally plant foods
  • to ensure vital body protein synthesis continues, it is advisable to combine plant sources of protein
26
Q

How should plant proteins be combined?

A
  • adults can combine plant proteins over the course of a day
  • young children should combine plant proteins at each meal
  • it is easy to combine plant sources of PRO to provide all the essential amino acids needed
  • combine plant sources of protein to provide a complete set of essential amino acids in your diet
27
Q

What is the primary limiting amino acid of grains, nuts & seeds?

A

Lysine

28
Q

What is the primary limiting amino acid of legumes and vegetables?

A

Methionine

29
Q

What are some benefits of plant proteins?

A
  • comes with fibre
  • lower SFA
  • no dietary cholesterol
  • increased phytochemicals
30
Q

What are some consequences of animal proteins?

A
  • lack of fibre
  • higher in SFA
  • contains dietary cholesterol
  • decreased phytochemicals
31
Q

How is the primary structure of proteins synthesized?

A
  • DNA is template for mRNA
  • mRNA copies instructions (transcription) for making PRO in cell
  • mRNA travels out of nucleus to ribosomes in cytoplasm
  • tRNA brings amino acids to mRNA along ribosomal machinery
  • amino acids lined up in sequence directed by mRNA
  • ribosome moves along mRNA, enzyme bonds amino acids to growing chain (translation) via peptide bonds
  • tRNA bring more amino acids to growing chain
  • once all amino acids have been added, protein is released from ribosome
  • amino acids’s linked together in 1000’s of different sequences (like the alphabet)
32
Q

What is the primary structure of a protein?

A

Amino Acid Sequence

33
Q

What is a peptide bond?

A

Condensation of 2 amino acids form a peptide bond.

34
Q

What is the secondary structure of a protein?

A
  • secondary structure represents localized segments
  • (e.g., coiled regions);
35
Q

What is the tertiary structure of proteins?

A
  • represents overall 3-D arrangement between subunits
36
Q

How do side chains of amino acids determine final 3-D structure of protein molecule?

A
  • attractive and repulsive forces at work
  • hydrophilic and hydrophobic characteristics depending on side chains
  • protein twists to take on most stable 3-D shape
  • protein bristles with positive and negative charges on its surface
  • 3-D shape stabilized by hydrogen and disulphide bonds between amino acids
  • final 3-D structure determines protein function in body
37
Q

What are the two major configurations of proteins?

A
  • two major configurations:
  • globular - spherical (e.g., immunoglobulins, Hb in RBC)
  • coiled or fibrous - linear (e.g., fibrinogen for blood clotting, tendons that attach bone to muscle)
38
Q

What is an aggregate protein?

A
  • Some proteins functional on their own
  • some need a mineral to be functional (e.g., Fe in Hb)
  • some join with other proteins to become active, called AGGREGATES (e.g., Hb, fibrinogen, ion channels)
  • (a.k.a. quaternary structure)
39
Q

How are proteins denatured, and when can it be beneficial?

A
  • uncoiling of 3D configuration due to exposure to heat, agitation, pH, heavy metals, alcohol or other conditions
  • may lead to loss of function of protein, depending on degree of denaturation
  • once a certain point of denaturation occurs, it is irreversible and protein loses function
  • denaturation can used as an advantage by body (e.g., stomach)
  • HCl acid denatures (uncoils) many forms of protein to increase exposure of the PRO to digestive enzymes (digestive enzymes in the small intestine digest the protein)
  • other examples: wine added to marinades – alcohol denatures the protein in meat and tenderizes it; lemon juice added to milk causes curdling (denaturing) of the milk proteins
  • denaturing of proteins in some foods may reduce their tendency to cause allergic reactions
40
Q

How are proteins digested?

A

Mouth

  • chewing
  • no digestion of protein

Stomach

  • hormone Gastrin stimulates secretion of gastric juices
  • HCl activates enzyme pepsin, which accounts for ~10% of PRO digestion

Small intestine

  • hormones: Secretin & CCK cause release of pancreatic juice into s.i.
  • pancreatic enzyme, trypsin digests proteins into di- & tri-peptides, amino-acids
  • di- & tri-peptides hydrolyzed by intestinal di- & tri-peptidase enzymes in lumen or by di- & tri-peptidases inside intestinal cells
41
Q

How are proteins absorbed and transported in the body?

A
  • amino acids actively transported across intestinal cells, ONLY SINGLE AMINO ACIDS enter bloodstream and travel to the liver for metabolism
42
Q

Discuss risk of food allergy of proteins.

A
  • immune response to part of a food PRO absorbed into the blood
  • immune system produces antibodies, histamines…
  • continuum of symptoms – from none to severe – from immediate to delayed
  • need to eliminate offending food(s)
  • children with food allergies diagnosed (antibody screening) before~3 years of age may outgrow allergy
43
Q

Discuss risk of food intolerance of proteins.

A
  • does not involve immune system (production of antibodies, etc.)
  • caused by non-protein substances in foods, digestive disorders or injury, or enzyme deficiencies
  • spectrum of symptoms: nausea, rapid pulserate, hives, headache…
  • avoid foods that cause symptoms (e.g., flavour enhancers, lactose)
44
Q

Discuss the role of protein as energy.

A
  • glucogenic amino acids used to form GLU via process of GLUCONEOGENESIS at times of low BGL
  • amino acids provide about 5% of body’s energy needs
  • deamination and breakdown of amino acids primarily occurs in liver cells
45
Q

How are proteins used for Growth, Maintenance, and Repair?

A
  • dying or injured cells replaced with new cells and new proteins
  • visual pigments (e.g., opsin)
  • collagen (e.g., bones, teeth, connective tissue, scar tissue, ligaments)
  • muscle (e.g., skeletal, smooth)
  • blood clotting (e.g., fibrin)
  • blood transport proteins (e.g., hemoglobin, transferrin, lipoproteins, albumin)
46
Q

Discuss the role of proteins as enzymes.

A
  • all enzymes are proteins
  • catalyze (accelerate) anabolic, catabolic, rearrangement and exchange reactions
  • recycled, not changed or consumed in the process
  • lock and key fit (induced fit model exists too) with substrate to produce end product
47
Q

Discuss the role of proteins as hormones.

A
  • chemical messengers, some hormones are protein-based
  • e.g., Insulin (51 amino acids)
  • e.g., Thyroid hormones (T3,T4) – help regulate metabolic rate
48
Q

Discuss the role of proteins in cell membranes.

A
  • “PRO islands in a sea of lipids”
  • some PRO act as receptors (e.g., for hormones, lipoproteins)
  • some PRO act as cellular pumps to help maintain electrolyte and fluid balance (e.g., sodium/potassium pump)
  • some PRO act as carriers for absorption of nutrients (e.g., GLU, GAL, FRU)
49
Q

Discuss the role of proteins in fuid balance.

A
  • water is attracted to partial charges on side chains of amino acids in proteins
  • blood proteins counteract forcing pressure of heart
  • reduces possibility of edema (“swollen tissue”)
  • blood PROs help maintain blood volume and blood pressure
50
Q

Discuss how proteins balance blood pH.

A
  • very narrow range pH 7.35-7.45
  • normal body processes produce acids and bases, carried in blood to lungs and kidneys for excretion
  • proteins can accept or donate H+ ions and act as blood BUFFERS
51
Q

Discuss the immune function of proteins.

A
  • antibodies (Ab) are large PRO molecules, respond to antigens (ex., bacteria, viruses, toxins, allergens)
  • adequate PRO nutrition needed for macrophage and Ab production
  • protein deficient diets and ANERGY often appear together
52
Q

What are the major roles of protein in the body?

A
  1. Vital Body Functions – Growth, Maintenance and Repair
  2. Enzymes
  3. Hormones
  4. Cell Membranes
  5. Body Fluid Balance
  6. pH Balance in Blood
  7. Immune function
  8. H. Formation of GLU/Provision of Energy
53
Q

What are food sources of protein?

A
54
Q

Compare plant and animal sources of protein.

A

Animal Sources – complete proteins

“high quality PRO” - provide all the essential amino acids in quantities needed by humans to support growth, maintenance and repair

Food examples:

  • meat – 100g serving provides ~20g PRO
  • fish – water-packed tuna is most PRO-dense food (>85% of kcal as PRO)
  • egg, large ~4g PRO
  • milk & milk products – 250mL glass of milk provides ~10g PRO– 175g yogurt ~9g PRO

Plant Sources – incomplete proteins

“low quality PRO”– lacking sufficient quantities of one or more eaa needed by humans to support growth, maintenance and repair – contain at least one “limiting amino acid”– need to combine plant proteins to get full complement of eaa in sufficient quantities to meet needs

– supply fibre, vitamins, minerals
– contain no cholesterol, usually low in SFA – generally supply <20% of kcal as PRO

Food examples:

  • kidney beans – 1 cup portion ~13g PRO
  • amaranth (grain) – 1 cup portion (cooked) ~10g PRO
  • almonds – 30 gram portion ~6g PRO
  • sunflower seeds – 1/2 cup portion ~8g PRO
55
Q

What are the DRI values for protein intake?

A

RDA

  • infants:
  • 0-6 months: 2.0g PRO/kg body weight
  • 6-12 months: 1.3g PRO/kg body weight
  • 1-3 years: 1.0g PRO/kg body weight
  • adults:
  • 0.8g PRO/kg body weight for adults
  • elite athletes or those with a large muscle mass may need to increase to 1.0-1.7g PRO/kg body weight
  • pregnancy & lactation: 1.1g PRO/kg body weight

AMDR

  • 10-35% of total EIN
56
Q

What are the health effects of high protein diets?

A
  • More animal foods = ­ increased SFA, dietary cholesterol, ­ and cost
  • Crowd out more nutrient-dense foods
  • Dehydrating
  • Promotes calcium loss from bone (inconclusive)— recommended ratio of Ca(mg):PRO(g) = 16:1
  • Increased potential for kidney damage
  • Perhaps increased risk of colon (& other) cancer
57
Q

What is marasmus?

A

Protein Energy Malnutrition (PEM)

  • 2 common PEM classifications:
  • MARASMUS = chronic
  • KWASHIORKOR = acute

The ‘skin & bones’ look that is characteristic of marasmus is apparent in this child.

58
Q

What is kwashiorkor?

A

Protein Energy Malnutrition (PEM)

  • 2 common PEM classifications:
  • MARASMUS = chronic
  • KWASHIORKOR = acute

The edema and enlarged liver characteristic of kwashiorkor are apparent in this child’s swollen belly.

59
Q

What are the contributing factors for protein energy malnutrition?

A
  • younger child’s high need for energy and protein
  • diets low in nutrients
  • infrequent food intake due to inadequate food supply, food inequity, poverty, food distribution issues, insufficient land to farm, natural disasters, etc.
  • infection – viral, bacterial, parasitic, fungal
  • inappropriate formula preparation
60
Q

What is PEM?

A
  • Protein Energy Malnutrition (PEM)
  • 2 common PEM classifications:
  • MARASMUS = chronic
  • KWASHIORKOR = acute
  • protein and energy malnutrition often seen together
  • usually occurs in early childhood
  • also seen in adults with disease conditions: HIV/AIDS, cancer, liver/kidney diseases, anorexia nervosa
61
Q

How to recover from PEM?

A
  • full or almost full recovery possible, if treated in time
  • if not treated in time – stunted physical growth and learning impairment
  • treatment: usually small amounts of CHO & PRO in form of skim milk, electrolytes & sanitized water fed first
  • dietary fat added later – need PRO carriers to move fat around

FNH 250 (11 decks)

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