3.1.4 proteins

Question 1

in terms of monomers and polymers what are proteins

Answer 1

poteins are polymers and are made of monomers called amino acids

Question 2

draw an amino acid representing the R group with an R

Answer 2

should have a carboxilic acid group , amine group and an alpha carbon with an R group attatched to it

Question 3

how many diffrent R groups are there , and also how many diffrent amino acids are there

Answer 3

20

Question 4

what bond is formed between amino acids and between which groups

Answer 4

polypeptide bond

between the carboxilic acid group and the amine group

Question 5

what type of reaction is need for a polypeptide bond

Answer 5

condensation reaction

Question 6

what are the four levels of structure of proteins

Answer 6

primary (found in all proteins)
secondary (found in all proteins)
tertiary (found in some proteins)
quarternary (found in some proteins)

Question 7

describe what primary structur is

Answer 7

The sequence (and number) of amino acids in the polypeptide chain is known as the primary structure, linked by peptide bonds only

Determines shape and function of protein

Question 8

describe what a secondary structure is

Answer 8

The chains fold into two different regular shapes – alpha helices (most common) and beta pleated sheets (less common).

H-bonding forms between the –CO and the -NH of adjacent amino acid. No R groups are involved.

These are found in all proteins (because all proteins have same backbone) and some proteins will have both helices and pleated sheets within their structure.

Secondary structure results in the R groups sticking out to the side ready to bond forming the tertiary structure.

Question 9

describe / draw out the structue of beta pleated sheets and alpha helicies

Answer 9

check with the internet ,

but one should form neatly crumpled sheets and one should form a helicies

Question 10

why are beta pleated sheets formed

Answer 10

The sheet is not flat but pleated because of the carbon having tetrahedral angles

Question 11

describe what a tertiary structure is

Answer 11

H-bonds (weak)

Ionic bonds (stronger and vulnerable to changes in pH)

Disulphide bridge (very strong, covalent bonds)

and hydrophobic interactions

Question 12

describe what a quaternary structure is

Answer 12

Where more than one (2 or more) polypeptide chains combine to form complexes

Joined by bonds similar to those in the tertiary structure

Only some proteins exhibit quaternary structure

For example, Haemoglobin consists of 4 polypeptide chains held by disulphide bridges and a non protein prosthetic group.

Question 13

what are the two main types of quarternary proteins

Answer 13

fibrous

globular

Question 14

describe the distinct featurs of fibrous proteins

Answer 14

Fibrous proteins such as collagen have structural roles, they consist of polypeptide chains linked in parallel chains or sheets with numerous cross links to make fibres

often have simular repeating units

collogen is used to link muscle of bone and to provide strength and flexibility.

Question 15

describe the distinct featurs of globular proteins

Answer 15

Globular proteins such as enzymes perform metabolic functions. Their shape is compact and folded - spherical.

e.g antibodys

Question 16

how do you test for proteins

Answer 16

add a solution that you wish to test in equal amounts of NaOH and copper (II) sulphate CuSO4

(could also say Biuret reagent )

purple means that theres proteins
while
light blue means theres no proteins

Question 17

info card (read and then try to recite as much as you can )

Answer 17

Fibrous :

Have structural functions e.g. keratin a resistant protein found in skin cells helps to prevent the entry of pathogens

The polypeptide chain has regular repetitive sequences and is coiled into a helix or pleated sheet - secondary structure. Sheets provide flexibility to the molecule

Structure maintained by H bonding

Parallel polypeptide chains cross linked to form long fibres, which provide strength

Stable ( less effected by pH changes and tempreature)

Usually insoluble in water (external R groups are non polar)

Question 18

info card (read and then try to recite as much as you can )

Answer 18

Globular :

Have metabolic functions e.g. enzymes such as amylase, hormones such as insulin

Polypeptide chains have irregular sequences of amino acids that form secondary and tertiary structures and have a specific 3d shape (tightly folded to form a spherical shape)

Structure maintained by H bonding, ionic bonds and disulphide bridges between atoms in R groups. Also hydrophobic bonds as their non polar R groups point inwards

Surface of the molecule has depressions in it into which other molecules can fit

Relatively unstable - 3d structure can be affected by temp and pH

Usually soluble in water (external R groups are polar)

Question 19

what are the main functions of proteins

Answer 19

Transport

Movement

Sensitivity and coordination (nervous system and the hormone system)

Reproduction

Protection (immune system)

Question 20

globular vs fibrous :

shape

Answer 20

GLOB :
messy rough

FIB :
long strands

Question 21

globular vs fibrous :

amino acid sequence

Answer 21

GLOB :
irregular and wide range of R groups

FIB :
repeated with limited range of R groups

Question 22

globular vs fibrous :
function

Answer 22

GLOB :
enzymes , hormones , immuno globlins , transport molecules

FIB:
structure

Question 23

globular vs fibrous :
examples

Answer 23

GLOB :
haemoglobin , enzymes ,antibodys , insulin

FIB :
kreatin , collogen , fibrin

Question 24

globular vs fibrous :
solubility

Answer 24

GLOB :
solubule in water generaly

FIB :
insoluable in water generaly