Amino Acids, protein structures

Question 1

What are all proteins formed from

Answer 1

All proteins are formed from amino acids

Question 2

How many different amino acids are there

Answer 2

There are 20 different amino acids

Question 3

Draw the general structure of an amino acid

Answer 3

https://studymind.co.uk/wp-content/uploads/2022/04/a-6.png

Question 4

What are the three main parts to an amino acid

Answer 4

Amine group (NH2)
Carboxyl group (COOH)
R group (the R group is different for each of the twenty amino acids)

Question 5

Which part of the amino acid is different for each of the twenty amino acids

Answer 5

The R group is different for each of the twenty amino acids

e.g. in glycine the R group is a carbon atom
in another one
carbon atom bonded to three hydrogen atoms

Question 6

Which parts/groups of an amino acid are the same for every amino acid

Answer 6

The amine group and carboxyl group are the same for every amino acid

Question 7

Describe the general structure of amino acids

Answer 7

Three main parts to an amino acid:

Amine group (NH2)

Carboxyl group (COOH)

R group (the R group is different for each of the twenty amino acids)

Question 8

What elements are present in proteins

Answer 8

They contain
carbon hydrogen nitrogen oxygen
Some amino acids also contain the element sulfur

Question 9

How amino acid molecules can bond together

Answer 9

Bond together by a peptide bond

Question 10

Describe how a peptide bond can be formed

Answer 10

Formed when two amino acids react together and form a chemical bond

h from amine group
and oh from carboxyl group is lost - to form water

The bond formed is called a peptide bond

A molecule of water is also formed. Therefore this is an example of a condensation reaction

formed when two amino acids are joined together

Question 11

When two amino acids are joined together, what is it called

Answer 11

The molecule formed when two amino acids join together/bonded together is called a dipeptide
Formed in a condensation reaction

Question 12

how are dipeptides formed

Answer 12

Dipeptides are formed by the condensation of two amino
acids.

Question 13

how are polypeptides formed

Answer 13

Polypeptides are formed by the condensation of many amino
acids.

Question 14

A condensation reaction between _______ amino acids forms _____

Answer 14

A condensation reaction between two amino acids forms a peptide
bond

Question 15

Draw the reaction between two amino acid molecules
label the bond formed

Answer 15

https://d1j63owfs0b5j3.cloudfront.net/term/images/630-1528466692706.png

Question 16

how many polypeptide chains may a functional protein contain

Answer 16

A functional protein may contain one or more polypeptides.

Question 17

Where does the reaction of the formation of a dipeptide occur

Answer 17

This reaction takes place in the ribosomes (which is where proteins are synthesised in cells)
The reaction is catalysed by a specific enzyme

Question 18

What is formed when three or more amino acids are joined together

Answer 18

A polypeptide - formed when three or more amino acids are chemically bonded/joined together -

1 molecule of water for every peptide bond formed

often consist of hundreds of amino acids joined together

Question 19

Describe how a peptide bond can be broken

Answer 19

Add water to the peptide bond
Breaks the peptide bond
Converts the dipeptide/polypeptide into original amino acids

Called a hydrolysis reaction

Question 20

Where do hydrolysis reactions for dipeptides/polypeptides occur in the body

Answer 20

This reaction is carried out by protease enzymes in the digestive system

Question 21

Difference between a polypeptide and protein

Answer 21

To be classed as a protein, a polypeptide has to fold into a complex, three dimensional shape

Once the polypeptide has folded into the correct shape - it can then carry out its function e.g. as an enzyme or a hormone

At this point, it would be referred as a protein molecule

Many proteins made from many different polypeptides forming a large and complex molecule
also contains other molecules to help carry out their function

Question 22

What are the different levels of protein structure

Answer 22

Primary structure
Secondary structure
Tertiary structure
Quaternary structure

Question 23

Describe what is meant by the primary

Answer 23

First level of protein structure is called the primary structure

The primary structure is the specific order of amino acids in a polypeptide

e.g. two polypeptides with different primary structures

a - b - c - d - a
a - a - b - d - c

Question 24

How is the primary structure really important for a protein

Answer 24

The primary structure is really important for a protein

This is because it helps to determine the final 3 dimensional shape of the protein molecule

And the shape of a protein is critical for its function

Even changing a single amino acid in the primary structure can change the final shape of the protein

this can prevent a protein from carrying out its function effectively

Question 25

What is the primary structure of a polypeptide determined by

Answer 25

The primary structure of a polypeptide is determined by the DNA sequence of the gene which encodes that polypeptide

Question 26

what is the secondary structure of proteins

how the secondary structure forms

Answer 26

In a/along the polypeptide chain, there are C=O groups and N-H groups

The oxygen atoms in the C=O groups have a small negative charge and

The hydrogen atoms in the N-H groups have a small positive charge

These positive and negative charges can attract each other

When this happens, hydrogen bonds form between amino acids all along the polypeptide chain

These hydrogen bonds cause the polypeptide chain to twist and fold into shapes.

These twists and folds are called the secondary structure

Question 27

What is secondary structure

Answer 27

When hydrogen bonds form between amino acids in the chain, it causes the chain to begins to coil into alpha helix or fold into a beta pleated sheet - secondary structure

where specific regions of the chain then fold

Question 28

examples of secondary structure

Answer 28

alpha -helix - polypeptide chain has twisted into a helical shape held in place by hydrogen bonds

beta-pleated sheet - the polypeptide chain folds into a flatter, sheet-like structure. Hydrogen bonds between amino acids hold the shape in place

https://as1.ftcdn.net/v2/jpg/03/85/95/74/1000_F_385957451_QtygFEaBpigMOyUSdbk7RRK4hZRfQUBg.jpg

Question 29

Can proteins have both alpha and beta pleated sheets

Answer 29

Many proteins have regions with alpha helices and beta-pleated sheets

Question 30

what does the type of secondary structure formed depend on

Answer 30

The type of secondary structure formed depends on the primary structure in that region

Certain amino acids tend to be found in alpha helices and others tend to be found in beta-pleated sheets

depends on amino acids present

Question 31

how is secondary structure stabalised

Answer 31

Secondary structure is stabilised by hydrogen bonding between different parts of the polypeptide chain

Question 32

what is meant by tertiary structure of proteins

Answer 32

The tertiary structure is the overall complex 3-dimensional shape of a polypeptide chain

1. when you have an unfolded polypeptide chain - has not started folding
2. first the chain folds into regions of secondary structure - alpha helix - beta-pleated sheet
3. once regions of secondary structure form, the chain now continues folding forming the final tertiary structure

https://as1.ftcdn.net/v2/jpg/03/85/95/74/1000_F_385957451_QtygFEaBpigMOyUSdbk7RRK4hZRfQUBg.jpg

tertiary structure contains 5 alpha helices wrapped in a very specific pattern around a beta pleated sheet

Question 33

explain why tertiary structure is important

Answer 33

The tertiary structure is important for how a protein functions.
E.g. the active site of an enzyme depends on the protein forming a very specific tertiary structure.

If we change the tertiary structure of an enzyme e.g by heating it, the the shape of the active site changes and the enzyme can no longer function effectively
enzyme has denatured

Question 34

what is meant by quaternary structure of proteins

Answer 34

some proteins consist of one polypeptide chain

however a large number of proteins consist of several different polypeptide chains working together as a large molecule

e.g. haemoglobin - formed from four polypeptide chains - these polypeptide chains are called subunits

_______
The quaternary structure shows how the individual subunits are arranged (fit together) AND also the position of any prosthetic groups to form a larger three dimensional complex protein molecule structure

quaternary structure only applies to proteins with at least two sub units

made from several different polypeptide chains held together by bonds

Question 35

what do some proteins also contain/what other molecules

prosthetic groups meaning

Answer 35

Some proteins contain other non-protein molecules forming part of the structure
These are called prosthetic groups and they help the protein to carry out its role

e.g. haemoglobin, contains the prosthetic group haem which bind to oxygen

Question 36

what are conjugated proteins

Answer 36

Proteins with a prosthetic group