Molecular Biology - Proteins

Which of these is the function of an amino acid dependent on?

variable R group

What type of amino acids have no polarity?

Hydrophobic

What makes an acidic amino acid acidic?

extra carboxyl groups

Why are basic amino acids positively charged?

extra amine groups

Why are hydrophilic amino acids uncharged?

the carboxyl and amino group charges cancel each other out

What do aromatic amino acids account for?

absorbance of proteins at 280 nm

What does the amino acid methionine do to amino acid chains?

initiates chains

What does the amino acid proline do to amino acid chains?

causes kinks in chains

What does the amino acid cysteine do to amino acid chains?

links chains together

What is a zwitterion?

an neutral ion with both positively and negatively charged parts

Which of the following is NOT a reason for water not being used as a buffer?

it dissociates reversibly

Why do amino acids have two pKa values?

they are zwitterions

Which of these is a characteristic of the primary structure of amino acids

all of these

Which of these is NOT a type of the secondary structure of protein?

α-sheet

What do secondary structures depend on?

hydrogen bonding

Which of these types of bonds do NOT stabilise the tertiary structure of proteins?

none of these

Interactions to make the quaternary structure are always what?

non-covalent

Which protein has the following; a compact structure, two chains held by S-S bonds, H-bonds and ionic bonds

insulin

In insulin, what is the A chain?

a compact unit around which the B chain is wrapped

What is the purpose of myoglobin and haemoglobin

binds oxygen (in muscle)

How many α-helices does myoglobin contain?

8

Which protein is the haem group NOT present

insulin

Which two elements act as allosteric inhibitors of oxygen binding?

H⁺ and CO₂

How do inhibitors affect the oxygen binding curve?

shift the curve to the right

Which immunoglobulin is abundant in plasma?

G

What is the combination of chains as the core unit of immunoglobulins?

one common light chains and three distinct heavy chains

Where does the antigen bind to on immunoglobulins?

the N-terminal domains

What can antibodies be cut by to generate Fab (antigen-binding region) and Fc (binds to cells)?

papain

What is glycosylation?

addition of a carbohydrate to a protein

Where does glycosylation occur?

endoplasmic reticulum and golgi apparatus

Where does the carbohydrate lie in IgG after glycosylation?

the Fc region

How many binding sites are on an allosteric protein?

two

What is a key characteristic of allosteric proteins?

conformational change

What do gene regulatory proteins do when bonded to DNA?

increase or decrease transcription

What shape are regulatory proteins to help bind then to DNA?

helical

What is a motif?

a simple combination of a few secondary structure elements