proteins

Question 1

Haemoglobin
- function?
- type of protein?
- number of polypeptide chains?
- prosthetic group/non-protein component?
- properties?
- does it have quaternary structure?
- is it conjugated?

Answer 1

• main function is to transport oxygen
• is a globular protein
• 4 polypeptide chains (2 alpha, 2 beta)
• has 4 haem groups containing Fe+ ions (the prosthetic group)
• the structure allows for reversible binding with oxygen
• solubule in water
• has quaternary structure
• is conjugated

Question 2

Elastin
- function?
- type of protein?
- number of polypeptide chains?
- prosthetic group/non-protein component?
- properties?
- does it have quaternary structure?
- is it conjugated?

Answer 2

• Function- allows structures to stretch when necessary, but allows them to return to their original size. E.G blood vessel walls, alveoli.
• Is fibrous
• has many polypeptide chains (do not need specific amount)
• no prosthetic group
• is elastic, flexible, and insolubule in water.
• has quaternary structure
• is not conjugated

Question 3

Collagen
- function?
- type of protein?
- number of polypeptide chains?
- prosthetic group/non-protein component?
- properties?
- does it have quaternary structure?
- is it conjugated?

Answer 3

• main function is that it will resist a chain in length under force, so gives high tensile strength. Is in skin, tendons, ligaments, etc
• fibrous
• 3 polypeptide chains
• no prosthetic group
• is inelastic, flexible, has high tensile strength, insoluble in water.
• has quaternary structure
• is not conjugated

Question 4

Keratin
- function?
- type of protein?
- number of polypeptide chains?
- prosthetic group/non-protein component?
- properties?
- does it have quaternary structure?
- is it conjugated?

Answer 4

• Main function is that it provides high tensile strength and toughness to structures like hair, nails, and teeth.
• fibrous
• many polypeptide chains (dont need to know exact amount)
• no prosthetic group
• inelastic, inflexible, high tensile strength, insoluble in water
• has quaternary structure
• not conjugated

Question 5

Insulin

• function?
• type of protein?
• number of polypeptide chains?
• prosthetic group/non-protein component?
• properties?
• does it have quaternary structure?
• is it conjugated?

Answer 5

• functions as a hormone, travels in the blood. Is released by the pancreas when blood sugar levels are too high. Causes sugar to be taken up from the blood and stored as glycogen.
• globular
• 2 polypeptide chains
• no prosthetic group
• soluble in water, specifc shape to bind to liver receptors
• has quaternary structure
• not conjugated

Question 6

amylase
- function?
- type of protein?
- number of polypeptide chains?
- prosthetic group/non-protein component?
- properties?
- does it have quaternary structure?
- is it conjugated?

Answer 6

• is an enzyme,it catalyses amylose and amylopectin in hydrolysis.
• is a globular protein
• 1 polypeptide chain
• prosthetic group is a chloride ion and a calcium ion.
• is solubule in water, it has a specifcally shaped active site in order to catylase amylose and amylopectin.
• no quaternary structure
• is conjucated

Question 7

catalase
- function?
- type of protein?
- number of polypeptide chains?
- prosthetic group/non-protein component?
- properties?
- does it have quaternary structure?
- is it conjugated?

Answer 7

• is an enzyme, which catalyses the breakdown of hydrogen peroxide (by product of metabolism)
• is a globular protein
• 4 polypeptide chains
• prosthetic group is 4 haem groups containing Fe2+
• has a specific shape, it is solubule in water.
• has quaternary structure
• is conjugated

Question 8

What is the general structure of an amino acid?

Answer 8

An amino acid has a central carbon (alpha carbon) attached to four groups: a hydrogen atom, a carboxylic acid group, an amine group, and a variable R-group.

The R-group varies between different amino acids.

Question 9

How many different amino acids occur in life?

Answer 9

20 different amino acids.

These amino acids are coded for by the DNA of life.

Question 10

What is a dipeptide?

Answer 10

A dipeptide is formed when two amino acids join together through a peptide bond.

It has an amine group at one end and a carboxyl group at the other.

Question 11

What is the definition of a polypeptide chain?

Answer 11

A polypeptide chain is a chain of many amino acids linked together by peptide bonds.

Polypeptides can often be hundreds of amino acids long.

Question 12

What is the primary structure of a protein?

Answer 12

The primary structure is the number and sequence of amino acids in the polypeptide chain.

It is held together by peptide bonds.

Question 13

What types of secondary structure can proteins have?

Answer 13

Alpha-helix and beta-pleated sheet.

These structures are held together by hydrogen bonds.

Question 14

What bonds hold the tertiary structure of a protein in place?

Answer 14

Hydrogen bonds, ionic bonds, disulfide bonds, hydrophobic associations, and hydrophilic associations.

These bonds are formed between the R-groups of amino acids.

Question 15

What is quaternary structure in proteins?

Answer 15

Quaternary structure refers to the binding of two or more polypeptide chains into one functional unit.

Each polypeptide chain in this structure is called a ‘subunit’.

Question 16

True or False: All proteins are made of one polypeptide chain.

Answer 16

False.

Some proteins consist of multiple polypeptide chains.

Question 17

Define globular protein.

Answer 17

Globular proteins have an irregular folding pattern and are roughly spherical in shape.

They are often soluble in water and have metabolic functions.

Question 18

Define fibrous protein.

Answer 18

Fibrous proteins are long fibers with a simple repeated sequence of amino acids and are insoluble in water.

They typically have structural functions.

Question 19

What is a prosthetic group?

Answer 19

A prosthetic group is a non-amino acid molecule that is permanently attached to a protein and is necessary for its function.

Examples include haem groups in hemoglobin.

Question 20

What is the Biuret test used for?

Answer 20

The Biuret test is used to detect the presence of peptide bonds in proteins.

A positive result shows a color change from pale blue to purple.

Question 21

Fill in the blank: Proteins contain the elements C, H, O, N and ____.

Answer 21

S

Question 22

What is the importance of the shape of proteins?

Answer 22

The specific shape of proteins allows them to perform their functions effectively.

Examples include enzyme active sites and receptor binding sites.

Question 23

What types of proteins are enzymes?

Answer 23

Enzymes are typically globular proteins that catalyze biochemical reactions.

They have specific active sites for substrate binding.

Question 24

Give three examples of fibrous proteins.

Answer 24

• Collagen
• Keratin
• Elastin

Question 25

What is a conjugated protein?

Answer 25

A conjugated protein is a protein that requires a prosthetic group to be functional. ## Footnote Haemoglobin is an example of a conjugated protein.

Question 26

How do hydrophobic R-groups contribute to protein structure?

Answer 26

Hydrophobic R-groups cluster together in the center of a protein, helping to maintain its shape. ## Footnote This clustering occurs to minimize contact with water.

Question 27

What type of bond forms between two R-groups that each contain sulfur atoms?

Answer 27

Disulfide bonds or bridges. ## Footnote These bonds are important for stabilizing tertiary structure.

Question 28

What is the role of the Golgi apparatus in protein modification?

Answer 28

The Golgi apparatus adds prosthetic groups to proteins, modifying them for proper function.

Question 29

what is primarys structure? how is it bonded?

Answer 29

- primary structure is the sequence of amino acids in the polypeptide chains. - it will influence how the polypeptide folds and therefore its final shape. - it is held together by peptide bonds.

Question 30

what is the secondary structure of a protein? what is it held together by?

Answer 30

- there are 2 shapes: alpha helices and beta-pleated sheets - held together by **H-bonds** between either within the polypeptide chain (pulling it into the coiled shape) or between 2 parallel polypeptide chains (creating the sheet shape)

Question 31

what is the tertiary structure of a protein? what are the bonds that hold it together?

Answer 31

- the **irregular folding** of a the polypeptide chain to create its overall 3D shape. - the shape is held together by bonds between R-groups There are 5 types of bonds that can occur between R groups: - **Hydrogen bonds**, between polar R-groups - **Ionic bonds**, between positively and negatively charged R-groups. Stronger than Hydrogen bonds, - **Disulphide bonds/bridges** covalents bonds between 2 R-groups that contain sulfur atoms. They are the strongest bond. - **Hydrophobic associations** where hydrophobic R-groups cluster together in the centre of a protein (away from water) - **Hydrophillic associations** between R-groups and their aqueous environment

Question 32

what is quaternary structure? How is it held together?

Answer 32

- occurs when a protein is made of **more than one polypeptide chain** - each polypeptide chain is considered a 'subunit' - the bonds that hold the subunits together are the same as the bonds between R-groups in tertiary structure (disulphide, hydrogen, ionic, hydrophillic, hydrohphobic)

Question 33

how does the primary structure affect the 3D shape of a polypeptide?

Answer 33

- the sequence of amino acids determines which bonds can form between R-groups, and where. - the location of the bonds between R-groups determines the shape the polypeptide chain is

Question 34

describe fibrous proteins - structure - functions - properties

Answer 34

- long fibres - simple, repeated structure of limited amino acids with small R-groups - regular structure, not folded into 3D shapes - insolubule in water - has structural functions

Question 35

describe globular proteins - structure - functions - properties

Answer 35

- **roughly spherical** - have a wide range of amino acids in their polypeptide chains - hydrophillic R-groups on outer surface - hydrphobic R-groups internally - **soluble** in water - tend to have **metabolic funtions**

Question 36

what is a prosthetic group?

Answer 36

- other molecules not made from amino acids needed for proteins to hold their correct shape and function - they are permanent parts of the structure

Question 37

what is a conjugated protein?

Answer 37

A protein that needs its prosthetic group in order to be functional.

Question 38

describe the biuret test for proteins in terms of what happens - what is biuret reagent? - how does it work?

Answer 38

- biuret reagent contains copper sulfate - the Cu2+ ions give the blue colour ***** - If peptide bonds are present, the Cu2+ ions will be reduced to Cu+ - in an alkaline solution, the ions form a complex with the nitrogen component of 4 peptide bonds. - the complex is purple, indicating the positive result.

Question 39

what is a proteome?

Answer 39

- all the possible proteins produced by any of the different cells of an organism at any stage in its life.

Question 40

what are the 4 groups the central carbon can be attatched to?

Answer 40

- carboxyl (OH and double bond O) - amine (2 hydrogens) - hydrogen (single) - R- group

Question 41

how are amino acids joined together?

Answer 41

- OH from one carboxyl, and H from the other amine group is removed . - they produce water - the C from the carboxyl and the N from the amine join to form a peptide bond