2.7 Proteins

Question 1

what is a protein

Answer 1

polymers composed of amino acid monomers

Question 2

what is an amino acid

Answer 2

has a central carbon atom
bonded to hydrogen + three functional groups
-amino acid (-NH2)
-acidic group (-COOH)
R group (single carbon to complicated ring structure)

Question 3

why is the R group significant in the amino acid

Answer 3

determines the uniqueness

Question 4

what are enzymes

Answer 4

proteins that speed up chemical reactions

Question 5

what are hormones

Answer 5

messengers that influence cellular metabolism

Question 6

name two structural proteins

Answer 6

keratin (makes up hair and nails)

collagen (lends support in ligaments, tendons, skin)

Question 7

describe actin and myosin

Answer 7

account for movement of cells and ability of our muscles to contract

Question 8

describe hemoglobin

Answer 8

a COMPLEX protein in our blood that transports oxygen

Question 9

what are antibodies

Answer 9

proteins that combine with foreign substances preventing them from destroying cells and upsetting homeostasis

Question 10

what are peptides

Answer 10

a chain of amino acids joined together by peptide bonds

Question 11

why do peptide bond unevenly

Answer 11

oxygen is more electronegative than nitrogen so H attached to N has slightly positive charge while O has slightly negative charge

Question 12

when are peptide bonds formed

Answer 12

amino acid group of one amino acid and carbonyl group of another amino acid

Question 13

describe the four levels of structural organization

Answer 13

primary structure
-linear sequence of amino acids
-joined by peptide bonds
secondary structure
-polypeptide takes on certain orientation in space
-hydrogen bonding between peptide bonds (alpha helix shape or beta folded shape)
tertiary structure
-final 3D shape
-bonding among R groups (ionic, covalent, hydrogen bonding) covalent: disulphide linkage
quaternary structure
-two or more polypeptides join to form a single protein

Question 14

what is a disulphide linkage

Answer 14

common form of covalent bond in tertiary structure (S-S) between two cysteine amino acids

Question 15

a) what is denatured and give 2 examples

b) when does it occur

Answer 15

a) proteins exposed to extremes in heat and pH they undergo irreversible change
ex) heating eggs cause egg white protein (albumin) to coagulate, adding acid to milk cause curdling

b) when normal bonding between R groups has been disturbed, once normal shape lost, no longer able to function normally

Question 16

what are prions

Answer 16

structures from the result of alternations in protein organization related to Alzheimer’s and “mad cow” disease

Question 17

what are the functions of proteins in plasma membrane

Answer 17

1. form channels that allow substances to enter/exit
2. carriers that transport molecules into/out cells
3. act as enzymes