Biochem 1: Proteins

Question 1

proteins are

Answer 1

polymers of 20 different amino acids (monomers) linked by peptide bonds

Question 2

polypeptide chain is a

Answer 2

single unbranched polymer of amino acids

Question 3

proteins consist of

Answer 3

one or more polypeptide chains folded into specific 3-D shapes

Question 4

what defines the shape of the protein

Answer 4

the sequence of amino acids

Question 5

polymers are formed by _____ reactions

Answer 5

condensation

Question 6

monomers are joined by covalent bonds, energy must be added, and water is removed, this is also called a ______ reaction

Answer 6

dehydration

Question 7

polymers are broken down into monomers in

Answer 7

hydrolysis reactions

hydrolysis releases energy

Question 8

protein primary structure

Answer 8

is a polypeptide chain

Question 9

protein secondary structure

Answer 9

occurs when the amino acid chain folds and coils in a helix or pleated sheet

Question 10

protein tertiary structure

Answer 10

occurs when the helix or sheet fold irregularly, forming disulfide bridges, hydrogen bonds, hydrophobic interaction, and ionic bonds between amino acids in the chain

Question 11

what 2 categories of proteins are there- divided into two large classes based on their three-dimensional structure

Answer 11

• fibrous proteins

- globular proteins

Question 12

protein quaternary structure

Answer 12

consists of two or more polypeptides

Question 13

proteins can undergo denaturation which is

Answer 13

occurs when proteins encounter hostile environments such as temperature and pH, and therefore lose their shapes and functions

Question 14

what structure does hydrolysis destroy?

what structure does denaturation destroy?

Answer 14

• hydrolysis destroys primary structure

- denaturation destroys all other levels of structure (but not primary) - because primary has covalent bonds

Question 15

globular proteins are proteins which are

Answer 15

folded to a more or less spherical shape

Question 16

globular protein properties and example

Answer 16

-they tend to be soluble in water and salt solutions

example is hemoglobin

Question 17

polar/nonpolar groups of globular proteins

Answer 17

• most of their polar side chains are on the outside and interact with the aqueous environment by hydrogen bonding and ion-dipole interactions
• most of their non polar side chains are buried inside

Question 18

fibrous proteins contain

Answer 18

polypeptide chains organized approximately parallel along a single axis

Question 19

properties of fibrous proteins

Answer 19

• consist of long fibers or large sheets
• tend to be mechanically strong
• are insoluble in water and dilute salt solutions
• play important structural roles in nature

Question 20

examples of fibrous proteins

Answer 20

• keratin of hair and wool

- collagen of connective tissues of animals including cartilage, bones, teeth, skin, and blood vessels

Question 21

collagen consists of

Answer 21

three polypeptide chains wrapped around each other in a replica twist to form a triple helix

Question 22

collagen structure specifics

Answer 22

• 30% of amino acids in each chain are Pro and hydroxyproline
• every third position is Gly
• each polypeptide chain is a helix
• the three strands are held together by hydrogen bonding

Question 23

collagen fibers with age

Answer 23

with age, collagen helices become crossed linked by covalent bonds formed between Lys and His residues

Question 24

where are crystallins found

Answer 24

in the epithelial and fiber cells of the ocular lens

Question 25

what are crystallins and what do they maintain

Answer 25

crystallins are structural, water soluble proteins

-maintain the elongated shape of lens fiber cells and lens structure and affect refraction of light

Question 26

crystalline proteins in the lens contain significant amounts of

Answer 26

Cys and Met

Question 27

what do molecular chaperons maintain

Answer 27

maintain normal conformation of other crystallins to prevent aggregation

Question 28

80-90% of the bulk of the eye contains

Answer 28

collagen

Question 29

collagen in the eye helps to

Answer 29

forms and maintains tissue structure, scaffolding and adhesion
-makes up the semiliquid gel of the vitreous humor

Question 30

in the corneal storm, collagen fibers form

Answer 30

lamellae sheets that impose cross-sectional strength

Question 31

collagen is also in ____, ___…. of the eye

Answer 31

in the sclera, ocular basement membranes called descemet’s membrane, lens capsule and blood vessels

Question 32

anchoring collagen fibrils attach:

Answer 32

basal epithelial cells of cornea and outermost lamellae of corneal stroma

Question 33

how senile cataracts form

Answer 33

• if oxidized, protein shape is altered through exposing more Cys sulfhydryl groups
• disulfide bonds form within and between crystallin protein
• high molecular weight aggregates are formed, which reduce the integrity and clarity of the lens itself

Question 34

hemoglobin basic structure

Answer 34

tetramer of two alpha chains and two beta chains, a2b2

-each chain has 1 heme group

Question 35

hemoglobin can bind up to __ molecules of ___

Answer 35

4 molecules of O2

Question 36

what is O2 positive cooperativity in hemoglobin

Answer 36

when one O2 is bound, it becomes easier for the next O2 to bind

Question 37

function of hemoglobin to

Answer 37

transport oxygen

Question 38

what affects the ability of Hb to bind and transport oxygen

Answer 38

H+, Co2, Cl-, and 2,3-biphosphoglycerate (BPG)

Question 39

the Bohr affect in binding affinity of O2 for Hb

Answer 39

H+ and CO2 bind to Hb and affect the binding affinity of Hb for O2

Question 40

Bohr affect in lungs

when hemoglobin binds to O2

Answer 40

actively metabolizing muscle: Hb releases O2

Question 41

Bohr affect in lungs

when hemoglobin releases H+

Answer 41

actively metabolizing muscle: Hb binds H+

Question 42

what are antibodies

Answer 42

are Y-shaped molecules consisting of two identical heavy chains and two identical light chains held together by disulfide bonds

Question 43

antibodies are classified as

Answer 43

glycoproteins

Question 44

what is the variable region of an antibody

Answer 44

the variable region is found at the prongs of the Y and is the part of the antibody that binds to the antigen

Question 45

the binding sites for the antibody on the antigen are called

Answer 45

epitopes

Question 46

the importance of correct folding

Answer 46

proteins that do not fold correctly may interact with other proteins in an undesired manner and aggregates may results