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Biochemistry > Unit 3 - IV. Amino Acids and Proteins > Flashcards

Unit 3 - IV. Amino Acids and Proteins Flashcards

1
Q

Amino acid

A
  • building blocks of protein
  • only 20 out of > 700 A.A. are found in human proteins
  • contains primary amine on one end and carboxylic acid group on the other
  • have optical isomers/enantiomers (L vs. D)
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2
Q

Zwitter ion

A
  • internal acid-base reaction of amino acids cause H from COOH to transfer to nitrogen atom in amine group allowing A.A. to be dipolar
  • Dipolar = both positive and negative charge in same molecule
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3
Q

isoelectric pH

A
  • isoelectric point
  • the pH at which an amino acid exists in solution as a zwitterion
  • depends on their classification (polarity) polar neutral/acidic/basic or nonpolar
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4
Q

Dipeptide

A
  • 2 amino acids
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5
Q

Tripeptide

A
  • 3 amino acids
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6
Q

Polypeptide

A
  • lots of amino acids (4-50)
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7
Q

Peptide Bond Formation

A
  • classified as a dehydration reaction
  • consists of the functional group, amide
  • peptide bond forms and water molecule is removed
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8
Q

Nonpolar amino acids

A
  • contain mostly hydrocarbon in their side chains
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9
Q

Polar neutral amino acids

A
  • contain either a hydroxyl group (-OH), a sulfhydryl group (-SH), or an amide group
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10
Q

Polar acidic amino acids

A
  • contain a carboxylic acid group
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11
Q

Polar basic amino acids

A
  • contain a primary or secondary amine group
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12
Q

Glycine

A
  • the simplest amino acid with a single hydrogen in the side chain
  • doesn’t fit into any of the classification categories
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13
Q

Contractile and Motile Role

A
  • muscle contraction

Proteins involved: F-actin, nebulin, tropomyosin, troponin, and myosin

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14
Q

Troponins

A
  • Consist of three subunits: Tropoinin I, T, and C.
  • subunits form a complex with actin and tropomyosin to create a large series of interconnected molecules that are responsible for muscle contraction
  • Troponin T can be measured to find MI and is just as good as measuring Troponin I
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15
Q

cTnI

A
  • cardiac troponin I
  • Regulates striated muscle contraction.
  • Has three isoforms.
  • Cardiac form of cTnI is never expressed in skeletal muscle.
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16
Q

cTnT

A
  • cardiac troponin T
  • Binds to tropomyosin.
  • Has three isoforms: skeletal (slow-and fast-twitch) and cardiac muscle.
  • In fetal development, the cardiac and skeletal forms are co expressed in both skeletal and cardiac tissues.
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17
Q

Structural Role

A

Proteins involved: elastin, collagen, keratin

  • elastin = resilience and ability to be stretched
  • collagen = strength
  • keratin = stability (insoluble)
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18
Q

Storage role

A
  • “vaults” where substances can be stored until needed

Proteins involved: Ferritin (iron), Casein (milk protein), ovalbumin (egg white protein)

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19
Q

Transportational role

A 
- carry other substances around the body
Protein involved:
- Hemoglobin (oxygen through blood)
- myoglobin (oxygen through muscles)
- serum albumin (Fatty acids through blood)
- transferrin (iron)
- ceruloplasmin (cooper)
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20
Q

Regulatory role

A

Proteins involved:

  • insulin (induce up take of glucose into cells)
  • somatotropin (growth hormone)
21
Q

Protective role

A

Proteins involved:

  • thrombin and fibrinogen (coagulation)
  • survivin (inhibits apoptosis)
22
Q

Primary Structure

A
  • sequence of amino acids in a protein (kind, #, and order)
23
Q

Significance of Insulin’s primary structure

A
  • the first protein to have its amino acid sequence deciphered
  • showed that the same protein in different species can be very similar
  • insulin from porcine and bovine were used by diabetics but over time the body would react immunologically against it
24
Q

Significance of Hemoglobin’s primary structure

A
  • showed that a substitution of 1 a.a. can cause a protein to malfunction (ex. sickle cell)
25
Q

Secondary structure

A 
- the special alignment of atoms in the backbone due to hydrogen bonding between the C=O of one peptide and N-H of another
3 Types:
- Alpha helix ( same chain)
- Beta pleated sheet (2 chains)
- Triple helix ( 3 chains)
26
Q

Tertiary structure

A
  • three dimensional shape as a result of folding and bonds from several types of bonding.
    Types of bonding:
  • Salt bridge = basic side chain + acidic side chain
  • disulfide bonds = two cysteine side chains
  • hydrophobic interactions = nonpolar side chains in polar environment
  • hydrogen bonds = two polar neutral or polar neutral + polar charged
27
Q

Quaternary structure

A
  • the number of subunits (polypeptide chains) and how they are held together (hydrogen bonds, salt bridges, and hydrophobic interactions)
28
Q

Denaturation

A
  • the disruption of the secondary, tertiary, and quaternary structures of a protein
    = results in loss of biological activity
  • primary structure remains intact
  • irreversible
    Types: Heat, pH effects, heavy metal salts, organic solvent, food enzymes
29
Q

Heat

A
  • disrupt hydrogen bonds and hydrophobic interactions
    + heat = rupture peptide bonds
  • Example: heating eggs
30
Q

pH effects

A
  • disrupt hydrogen bonds and salt bridges resulting in coagulation
  • Example: acid + milk = casein (milk protein) or adding KOH to eggs
31
Q

Heavy metal salts

A
  • disrupt salt bridges and covalent disulfide bonds

- Example: silver nitrate added to eggs

32
Q

Organic solvents

A
  • form hydrogen bonds = compete with naturally occurring hydrogen bonds
  • used as (alcohol) disinfectants because it denatures and coagulates protein in bacterial cell walls
  • Example: 2-propanol added to eggs
33
Q

Food enzymes

A
  • hydrolyze peptide bonds disrupting primary structure (and therefore 2, 3, and 4 structures)
  • example: meat tenderizer (papain from papaya) or pineapple (bromelain) added to eggs
34
Q

C-reactive protein (CRP)

A
  • positive acute-phase reactant protein synthesized in liver
  • elevated in inflammation, infection or injury
  • CRP test used to monitor wound healing, surgical incisions, organ transplants, burns, and early detection of infection
  • predictor (not diagnostic) of atherosclerosis because inflammation can be caused by coronary vessel pathogens, myocardial necrosis/ischemia etc.
  • CRP presence in arterial wall predicts severity of atherosclerosis
35
Q

Hs-CRP

A
  • high sensitivity C-reative protein
  • test assesses the connection between high CRP levels and risk of cardiovascular disease (detects small amounts of CRP to evaluate CV risk)
36
Q

Total protein

A
  • 3 components: Prealbumin, albumin, and globulin
  • Total protein = albumin + globulin
  • used to monitor liver disease, kidney disease, malnutrition, and chronic edema
  • serum protein electrophoresis = 5 bands (- gamma, beta, alpha 2 , alpha 1, albumin +)
37
Q

Prealbumin

A
  • transports thyroxine and vitamine A
  • has a short half life (2 days) and can be used to monitor patients nutritional status
  • increase during pregnancy, chronic kidney disease, nephrotic syndrome, and hodgkins status
  • decrease during liver diseases, malnutrition, and acute inflammation
38
Q

albumin

A
  • most abundant plasma protein
  • synthesized in liver
  • helps maintain oncotic pressure which pulls water into the circulatory system
  • also transports vitamin B6, Zn 2+, Ca 2+, fatty acids, drugs, and hormones
  • increases during dehydration
  • decreases malnutrition and various liver disease
39
Q

globulins

A
  • increase during acute/chronic infections/inflammation, cirrhosis of liver, and various malignancies (ex: hodgkin’s, leukemia, lymphomas)
  • decrease malnutrition, wilson’s disease
    3 types: alpha, beta, gamma
    alpha globulins = alpha1, antitrypsin, ceruloplasmin, cholinesterase, and prothrombin
    beta globulins = complement proteins, fibrinogen, plasminogen, and transferrin
    gamma globulins = antibodies
40
Q

alpha 1-antitrypsin

A
  • antiprotease activity against chymotrypsin, kallikrein, renin, and plasmin
  • increase in inflammatory disease
  • decrease in lung and liver disease
41
Q

ceruloplasmin

A
  • copper containing protein
  • functions in redox reactions
  • regulates the ionic state of iron and its incorporation into transferrin
  • increases in APR (late reacting) and by estrogen
  • decreases inWilson disease (hepatolenticular degeneration) where copper deposits into tissue (of liver and eye)
42
Q

Transferrin

A
  • plasma transport protein of the iron
  • synthesized in liver
  • useful for differential diagnosis of anemia and monitoring treatment of anemia
  • increase in iron deficiency
43
Q

Natriuretic peptides

A
  • majority are cardiac peptides
  • increase after MI, chronic Hypertension, CHF
  • includes ANP (arterial) and BNP (brain)
44
Q

BNP

A
  • B type natriuretic peptide
  • Dilate blood vessels
  • Increase the excretion of sodium and fluids
  • Reduce concentrations of neurohormones that lead to: Vessel constriction, Fluid retention, Elevated blood pressure
  • increases with CHF
  • used to distinguish shortness of breath due to CHF (normal with other pulmonary causes)
45
Q

Cytokines

A
  • proteins that play a role in intercellular signalling
  • 5 categories that have functions that overlap:
    1. interferons
    2. interleukins
    3. chemokines
    4. colony-stimulation factor
    5. tumor necrosis factor (TNF)
46
Q

Homocysteine

A
  • sulphur containing amino acid produced via remethylation and transsulfuration of methionine (SAM)
47
Q

Hyperhomocysteinemia

A
  • caused by folate deficiency, enzyme deficiencies and a variety of drugs, solvents, toxins
  • risk factors include physiologic, genetic, clinical conditions, and life style
48
Q

Myoglobin

A
  • complex oxygen binding protein present in cardiac/skeletal muscle
  • excreted in urine
  • nephrotoxic
  • useful for early detection of MI (3 hrs) but is cleared rapidly and has lower specificity

Biochemistry (14 decks)

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