Module 1 sem 1 exam (macromolecules and plasma membrane)

Question 1

Describe the structure and function of plasma membrane (have diagram look over)

Answer 1

-Border of cell separating internal and external environments
-selective, differentially permeable lipid bilayer
-Controls entry and exit ions, e.g. Na+, K+, Ca+
-Passive/active control of substances into cell

Question 2

Describe membrane lipids. Mention phospholipids

Answer 2

-Hydrophilic (polar) phosphate heads face H2O on each side of membrane
-Hydrophobic fatty acid tails directed towards centre

Question 3

What are two types of membrane lipids? Describe them in the bilayer

Answer 3

Cholesterol
-Holds phospholipids still, can stiffen membrane

Glycolipids
-Phospholipids with short carbohydrate chains on extracellular face
-Contributes to glycocalyx-carbohydrate coating on cell surface

Question 4

Describe integral membrane proteins

Answer 4

penetrate membrane
-Transmem proteins pass through
-Hydrophilic regions contact cytoplasm + extracellular
-Hydrophobic regions pass through lipid of membrane
-Some drift in membrane other anchored to cytoskeleton

Question 5

Describe peripheral membrane proteins

Answer 5

adhere to one face of membrane
-do not penetrate membrane
-usually tethered to cytoskeleton

Question 6

Provide functions of protein membranes

Answer 6

-Anchoring proteins (support)

-Recognition proteins (self)

-Secondary messenger systems-communicate within cell receiving chem message

-Enzymes: catalyse reactions
-Receptor proteins: bind chem signals

-Carrier proteins: bind solutes and transfer them across membrane

-Cell-adhesion molecules: mechanically link cell to extracellular material

-Channels: allow hydrophilic solutes and water to pass through membrane

Question 7

Define protein in terms of amino acids, peptide, peptide bonds

Answer 7

polymer of amino acids
a.acid: central C with 3 attachments amino, carboxyl, radical group (determines properties of amino)

peptide: molecule comprising two/more amino acids joined by pep. bond

pep. bond: joins amino acid to carboxyl group of next amino (formed by dehydration synthesis)

Question 8

Describe protein structure (not the 4 types). Define denaturation

Answer 8

unique, three dimensional shape crucial to function
-reversibly change conformation therefore function
e.g. muscle contraction

denaturation (extreme conformational change that destroys function)

Question 9

Describe protein primary structure

Answer 9

sequence of amino acids encoded in genes

Question 10

Describe protein secondary structure

Answer 10

coiled/folded shape held together by H bonds between slightly neg (C=O) and slightly pos (N-H) groups
-alpha helix (spring like) or beta helix (pleated, ribbon like)

Question 11

Describe protein tertiary structure

Answer 11

further bending/folding of proteins into globular shapes due to hydrophobic-hydrophilic interactions and Vander Waals force

Question 12

Define globular and fibrous proteins

Answer 12

globular: within cell membrane/move freely in body fluids

fibrous: slender filaments suited for roles in muscle contraction and skin/hair strengthening

Question 13

Describe protein quaternary structure

Answer 13

associations of two or more polypeptide chains due to ionic bonds and hydrophobic-hydrophilic interactions
-only occurs in some proteins

Question 14

Describe 4 protein functions

Answer 14

structure: keratin- tough
collagen- deeper layers of skin, bones, cartilage

cell adhesion: bind cells together

membrane transport

recognition:(antibodies=proteins)