Proteins

Question 1

proteins are the links between

Answer 1

genotype and phenotype

Question 2

gene expression

Answer 2

• process by which proteins are DNA directs protein synthesis
• two stages: transcription and translation

Question 3

why can’t proteins be directly translated from DNA

Answer 3

• use of RNA protects DNA and its genetic material
• allows more proteins to be created simultaneously

Question 4

amino acid

Answer 4

• 20 types
• order determines the protein formed

Question 5

peptide bond

Answer 5

• bonds between amino acids
• form between the hydrogen and carboxyl groups

Question 6

polypeptide

Answer 6

• protein composed of one or more long chains

Question 7

(blanks) provide the instructions to make certain proteins

Answer 7

genes

Question 8

protein shape determines (blank)

Answer 8

function

Question 9

primary structure

Answer 9

• describes order of amino acids
• any of 20 amino acids can appear at a position in the protein
• primary structure for protein antidiuretic hormone (ADH) can be written as Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly

* important to note side groups don’t play a role in peptide strucutre, but do play a role in primary structure

Question 10

secondary structure

Answer 10

• 3D shape
• results from hydrogen bonding between amino and carboxyl groups of adjacent amino acids
• bonding produces either

spiral (alpha helix): when hydrogen bonds form in a chain

OR

folded plane that looks like pleats on a skirt (beta pleated sheet): parallel chains linked into pleated shape

• protein whose shapes are dominate by two patterns often form fibrous proteins

Question 11

tertiary structure

Answer 11

• additional 3D shaping
• often dominates structure of globular proteins
• factors that contribute to tertiary

= hydrogen bonding between R groups of amino acids

= iconic bonding between R groups of amino acids

= hydrophobic effect: occurs when sulfur atom in amino acid cysteine bonds to sulfur atom in a nother cysteine (forming cysteine, kind of double amino acid); disulfide bridge helps maintain folds of amino acid chain

Question 12

quaternary structure

Answer 12

• describes protein that is assembled from two or more separate peptide chains

• ex. globular protein hemoglobin consists of four peptide chains that are held together by hydrogen bonding and interactions among R groups

Question 13

structural -

¹/₇ major functions of proteins

Answer 13

support

keratin in the hair and horns of animals

collagen in connective tissues

silk in spider webs

Question 14

storage -

²/₇ major functions of proteins

Answer 14

holds/collects molecules like calcium and iron

casein in milk

ovalbumin in egg whites

zein in corn seeds

Question 15

transport -

³/₇ major functions of proteins

Answer 15

moves certain small molecules/ions

in membranes of cells that transport materials into and out of cells
oxygen carrying hemoglobin in red blood cells

proton pump

Question 16

motion -

⁶/₇ major functions of proteins

Answer 16

contract muscles

actin

myosin

Question 17

defense -

⁴/₇ major functions of proteins

Answer 17

recognizes foreign substances; center of immune system

antibodies that provide protection against foreign substances that enter bodies of animals

immunoglobulins

Question 18

regulation -

⁷/₇ major functions of proteins

Answer 18

receives or sends information to regulate body functions

hormones

Question 19

enzyme catalysis -

⁵/₇ major functions of proteins

Answer 19

facilitates or speeds up certain chemical reactions

enzymes

Question 20

denaturation

Answer 20

• proteins unfolding
• can occur if pH, ionic concentration, or temperature change
• leads to biologically inactive proteins
• most enzymes can only function in specific conditions

Question 21

channel proteins

Answer 21

• provide open passageways through membrane for certain hydrophilic (water-soluable) substances such as polar and charged molecules

aquaporins are channel proteins of certain cells (such as those in kidneys and plant roots) that dramatically increase the passage rate of H2O molecules

Question 22

ion channels

Answer 22

• allow passage of ions across membrane

in nerve and muscle cells, ion channels called gated channels open and close in response to specific chemical or electrical stimuli to allow passage of specific ions (like Na+ and K+)

Question 23

carrier proteins

Answer 23

• bind to specific molecules
• transferred across membrane after carrier protein undergoes change of shape

passage of glucose into cells is by carrier protein

Question 24

transport proteins

Answer 24

• use energy in form of ATP (adenosine triphosphate)
• transport materials across membrane
• when energy used, materials said to be actively transported through active transport

sodium potassium pump uses ATP to maintain higher concentrations of Na+ and K+ on opposite sides of plasma membrane

Question 25

recognition proteins

Answer 25

• give each cell type unique identification
• identification provides for distinction between cell types
• between self and foreign cells, normal cells and those infected with a virus
• recognition proteins are actually glycoproteins, proteins with short polysaccharide chains that extend away from surface of membrane

differences between blood types are result of recognition proteins on surface of red blood cells

Question 26

receptor proteins

Answer 26

• provide binding sites for hormones or other trigger molecules
• in response to hormone or trigger molecule, specific cell response is activated

Question 27

adhesion proteins

Answer 27

• attach cells to neighboring cells
• also provide anchors for internal filaments and tubules that give stability to the cell

Question 28

molecular chain of command in a cell

Answer 28

DNA ⇒ RNA ⇒ protein