Protein Structure Flashcards
What is the monomer of a protein
Amino acid
When does a dipeptide form?
When two amino acids join together
When does a polypeptide form?
When more than two amino acids join together
What are proteins made up of?
One or more popypeptides
Draw the structure of an amino acid
A carboxyl group joined to an amine group and an R group
How are polypeptides formed + describe?
Condensation reaction
A molecule of water is released during the reaction
Draw two amino acids undergoing a condensation reaction
…
Describe the primary structure of a protein
The sequence of amino acids in a polypeptide chain - joined by peptide bonds
Describe the secondary structure of a protein
Folding of the primary structure into an alpha helix or beta pleated sheet held together by hydrogen bonds
Describe the tertiary structure of a protein
Folding into a 3D structure using: Hydrogen bonds Disulfide bridges Ionic bonds Hydrophobic and hydrophilic interactions
Describe the quaternary structure of a protein
Several popypeptides held together by bonds
Describe ionic bonds
Attractions between negative and positive charges on different parts of the molecule
Describe disulfide bridges
When two molecules of cysteine (amino acid) come close together, the sulfur atim in one systeine bonds to the sulfur in the other cysteine
Describe hydrophobic and hydrophilic interactions
When hydrophobic groups are close they clump together so that hydrophilic groups are pushed to the outside - affects the final folding of the protein
How does a proteins primary structure determine its 3D structure
Amino acid sequence determines what bonds will form and how the protein will fold which affects its properties
What are globular proteins?
Round, compact proteins made up of multiple polypeptide chains
What are the polypeptide chains like in globular proteins? + what does this mean?
They are coiled so that the hydrophobic parts face inwards and the hydrophilic parts face outwards allowing the protein to be soluble
Give an example of a globular protein
Hameoglobin:
Made of 4 polypeptide chains
Iron-containing haem groups that carry oxygen in the blood
What are fibrous proteins?
Long insoluble polypeptide chains that are tightly coiled to form a rope shale
What are the polypeptide chains like in fibrous proteins?
Held together by lots of bonds eg. Hydrogen and disulfide making the protein strong
Where are fibrous proteins found?
In supportive tissue
Give an example of a fibrous protein
Collagen is a strong, fibrous protein that forms connective tissuw
What do enzymes do?
Catalyse metabolic reactions on a cellular level (respiration) and on a body lebel (digestion)
What is a catalyst?
A substance that speeds up a chemical reaction without being used up in the reaction itself
What makes enzymes highly specific?
Tertiary structure
What is the active site?
The part of the enzyme where the substrate molecules bind to
How do enzymes speed up the rate of reaction?
They lower activation energy making the reactions happen at a lower temperature
How does an enzyme-substrate compelx lower the activation energy x2
- if two substrates need joining, being attached to enzyme holds them closer together reducing repulsion between the molecules so can bond easier
- if enzyme catalsyses a breakdown reaction, active sites put a strain on bonds so substrate molecules breaks easier
Describe the lock and key model
The substrate fits into the enzyme the way a key fits into a lock
Describe the induced fit theory
The active site changes shape as the substrate binds
What determined the active sites shape?
The tertiary strucutr ehich is determined by the primary structure
What is the primary sturcture determined by?
A gene - if a mutation occurs then the tertiary structure could be altered
