Proteins

Question 1

What are the seven (7) important functions of proteins?

Answer 1

• structural support
• storage
• transport of substances (facilitated diffusion, active transport)
• intercellular signals
• movement (muscles)
• Defense against foreign substances
• act as Enzymes

Question 2

What is hemoglobin?

Answer 2

A protein in blood cells that carries oxygen from one place to another in mammals

Question 3

What is keratin?

Answer 3

The most common protein found in vertebrates, in hair and fingernails.

Question 4

What is Fibrin?

Answer 4

Protein that assists with blood clotting, and collagen (protein component in bones, skin, ligaments and tendons)

Question 5

What determines a protein’s function?

Answer 5

The structural characteristics of each amino acid that makes up a polypeptide chain

Question 6

What groups make up an amino acid?

Answer 6

• Carboxyl group
• A hydrogen group
• An amino group
• A side (R) group

Question 7

How many different amino acids can be found in animals?

Answer 7

20 different amino acids

Question 8

Why are amino acids considered amphiprotic?

Answer 8

They posses both carboxyl (acidic) and amino (basic) functional groups.

Question 9

What are the three (3) different electrostatic characteristics of amino acids?

Answer 9

• Hydrophilic (polar)
• Hydrophobic (non polar)
• Charged (acidic [negative charge] or basic [positive charge])

Question 10

What is the name of the amino acid whose side chain forms a covalent bond with its own amino group

Answer 10

Proline (pro)

Question 11

What functional group do acidic amino acids have as their side chain?

Answer 11

Carboxyl group

Question 12

What functional group do basic amino acids have as their side chain?

Answer 12

Amino group

Question 13

Jeopardy:

The three dimensional shape of a protein that is determined by the sequence of amino acids it contains

Answer 13

What is conformation?

Question 14

Jeopardy:

An amino acid polymer

Answer 14

What is a polypeptide?

Question 15

What is the process of protein synthesis?

Answer 15

When polypeptides are constructed in the cytoplasm of cells

Question 16

What are the 8 essential amino acids?

Answer 16

• Tryptophan
• Methionine
• Valine
• Threonine
• Phenylalanine
• Leucine
• Isoleucine
• Lysine

Question 17

What process involves the joining of amino acids together using what three organelles?

Answer 17

The process of protein synthesis directs ribosomes, RNA and enzymes to join amino acids together

Question 18

The bond between amino acids is called _____

Answer 18

peptide bonds (amide linkage)

Question 19

How are peptide bonds formed?

Answer 19

They are formed by the condensation reaction between an amino group in one amino acid and the carboxyl group of an adjacent amino acid

Question 20

Name of bond between an amino group in one amino acid and the carboxyl group of an adjacent amino acid.

Answer 20

Amide bond

Question 21

A polypeptide chain will always have a(n) __________ at one end and a(n) __________ at the other. These are called ________ and _________

Answer 21

an amino group (A-terminus) at one end and a carboxyl group (C-terminus) at the other end

Question 22

Jeopardy:

Round, spherical polypeptide chains

Answer 22

What are globular proteins?

Question 23

Each of the amino acids in a polypeptide is referred to as _______

Answer 23

A residue

Question 24

Why is the final conformation of protein sensitive to its primary structure? How does this apply to sickle cell anemia?

Answer 24

When the sequence of one amino acid is changed, the 3D structure of the polypeptide chain will also be changed making the protein (overall polypeptide chain(s)) lose its function. For ex: sickle cell anemia: the red blood cells become deformed and block the blood vessels impeding blood flow in the body.

Question 25

During protein synthesis, amino acids are added to the chain ___ ___ _ ______

Answer 25

one at a time

Question 26

True/False: | A primary structure has folds and coils.

Answer 26

False: | Secondary structures are characterized by their folds and coils

Question 27

In a secondary structure, what causes the polypeptide chains to form folds and coils?

Answer 27

Hydrogen bonds between the electropositive hydrogen of the amino group (N-H) four peptide bonds away and the electronegative oxygen atom of the carboxyl group (C=O) of one peptide bond

Question 28

What is an a-helix?

Answer 28

Hydrogen bonds, repeated over a specific length of a polypeptide chain, causing structures to bend and form coiled structures.

Question 29

Give two (2) examples of a-helix

Answer 29

a-keratin a fibrous protein found in hair is almost completely shaped into an a-helix. An enzyme called lysozyme, a globular protein, acts as a disinfectant in sweat, saliva, and tears. It has areas of a-helix that are separated by B-pleated sheets.

Question 30

How are B-pleated sheets formed?

Answer 30

This type of secondary structure is formed by polypeptide chains situated parallel to each other

Question 31

How are hydrogen bonds formed in B-pleated sheets?

Answer 31

In this case, the oxygen atom from the carboxyl group at one strand bonds with the hydrogen atom from the amino groups on an adjacent strand

Question 32

Give an example of B-pleated sheets

Answer 32

The silk in spider web, a type of fibrous proteins, has many B-pleated sheets with hydrogen bonds. These bonds make the silk in spider webs stronger than steel. Spider webs can stretch farther than steel before breaking.

Question 33

What type of proteins are characterized by their levels of structure? Name these levels of structure.

Answer 33

Globular proteins are characterized by their four levels of structure: - Primary structure - Secondary structure - Tertiary structure - Quaternary structure

Question 34

How are tertiary structures formed?

Answer 34

Attraction and repulsion between the polypeptide and its environment causes the structure to be supercoiled

Question 35

How are tertiary structures made stable?

Answer 35

They are stabilized by a number of different R-group interactions

Question 36

How are two cysteine residues stabilizers of tertiary structures?

Answer 36

The sulfur in the R-groups of two cysteine residues will attract each other and form a disulfide bridge (covalent bond of two sulfurs) which are strong stabilizers of tertiary structures.

Question 37

How does proline (pro) contribute to the shape of tertiary structures?

Answer 37

Proline's R group bonds with its amino group. This bond creates a kink in proline's structure which helps with shaping tertiary structures

Question 38

Jeopardy: | Two or more polypeptide subunits forming a functional protein

Answer 38

Quaternary structure

Question 39

Give four (4) examples of proteins that are in a quaternary structure

Answer 39

- Collagen - Keratin - Hemoglobin (globular proteins)

Question 40

Give three (3) examples of proteins that are in a quaternary structure

Answer 40

- Collagen - Keratin - Hemoglobin (globular proteins)

Question 41

What may cause proteins to unravel?

Answer 41

Proteins may unravel due to higher or lower than normal temperatures, pH levels, ionic concentration and other factors in their surroundings.

Question 42

What is the effect of the unravelling of proteins called?

Answer 42

Denaturation

Question 43

Under what circumstances are denatured proteins able to regain their shapes?

Answer 43

When the denaturing agents such as heat or chemicals are removed from the protein, the denatured protein is able to regain its shape as long as its primary structure is still intact

Question 44

What will cause a protein to be destroyed?

Answer 44

If the denaturing agent destroys the peptide bonds between the amino acids, then the protein will be destroyed.

Question 45

Give 2 examples of when protein denaturation becomes useful.

Answer 45

Curing meats by applying high concentrations of salt or sugar preserves the food by killing or denaturing the enzymes in the bacteria that would spoil the food quickly. Blanching fruits and/or vegetables by quickly dropping and removing them from hot water denatures the enzymes that would cause them to turn brown in the atmosphere.

Question 46

Jeopardy: | Proteins that help the growing polypeptide to fold into a tertiary structure

Answer 46

What are chaperone proteins?

Question 47

What is the primary purpose of cooking?

Answer 47

To denature the fibrous proteins in muscle cells of meat that make them hard to chew

Question 48

What is used to determine a protein sequence, why is it used?

Answer 48

PITC - phenylisothiocyanate - is used to determine protein sequences because it attaches to a residue without destroying the rest of the peptide bonds, and so scientists are able to identify each of the amino acids and the order in which they are organized in the polypeptide chain.

Question 49

Why do egg whites turn white and solid when heated?

Answer 49

Heat denatures the protein, albumin, in the egg white and causes the protein structures to uncoil, which then gets tangled with each other and block light rays or become opaque.