Proteins Flashcards
Thursday 5th September 2019
Name the parts of amino acids
Amine, hydrogen, carboxyl, R-group (variant). Carbon centre
What is a:
a) Condensation reaction
b) Hydrolysis reaction
a) When 2 biological molecules join together to lose water
b) When 2 biological molecules spit apart by adding water
What does proteinogenic mean?
The 20 amino acids which in different combinations make up all proteins in humans
How many different amino acids are there in humans?
20 - the different combinations form the different proteins
Where are proteins found in the body?
DNA (protein around it), digested in the small intestine & stomach, amino acids making them in the ribosomes, enzymes, anitbodies, antigens - surface of cells, haemoglobin, cologen (in skin)
What are the base elements for amino acids?
Carbon, Hydrogen, Oxygen, Nitrogen
Why is the shape of a enzyme important for its function?
Only the appropriate substrate will fit in the enzyme’s active site & and be broken down into its products
What is an amino acid residue?
(Primary stage) when 2 amino acids join in a condenstaion reaction, a water molecule is lost. The 2 separate parts of the amino acid left before the peptide bond is formed are amino acid residues
What bond is formed in proteins?
Peptide bonds
Describe the process of a condensation reaction between 2 amino acids (primary stage)
2 amino acids (monomers) come together. The hydroxyl from the carboxyl section joins to a hydrogen from the amine section of the other amino acid. They break off from the amino acids to form a water molecule. The amino acid residues left form a peptide bond to the exposed carbon in the carboxyl section, and the exposed nitrogen from the amine section. This is now a dipeptide formed from the condensation reaction
We eat food to get proteins, to break into amino acids and be reused. How do plants make proteins?
They absorb nitrogen from the soil, so can make their own amino acids from scratch
What is the R group?
The varying group between all amino acids (below the centre carbon)
What is the (briefly):
1) Primary structure
2) Secondary structure
3) Tertiary structure
4) Quaternary structure
1) Condensation reaction - 2 amino acids join (peptide bond) to form a dipeptide
2) H bonds form between remains of carboxyl & hydroxyl groups of the polypeptides, forming an alpha helix or beta pleated sheet
3) Disulfide bridges, H bonds & ionic bonds form between R groups, so the protein is twisted and folded & 3D
4) Not essential! When a protein is made from more than one type of polypeptide chain e.g. prosthetic group. Same as tertiary stricture bonds
What happens in the secondary structure?
Either alpha helix or beta pleated sheet shapes form from hydrogen bonds made from the remains of the carboxyl and hydroxyl groups
What happens if the secondary structure fails - the hydrogen bonds break (which can happen as they’re weak)?
Any change n the environment could cause this. The protein would unfold completely, becoming flat again
Where are the hydrogen bonds formed in secondary structure?
Between the remains of the carboxyl and hydroxyl groups
What happens in the tertiary structure?
Disulfide bridges, hydrogen bonds and ionic bonds form between R groups of amino acids, causing the structure to twist and fold, becoming more 3D
Talk about these types of bonds:
a) Hydrogen bonds
b) Ionic bonds:
c) Disulfide bridges
All formed in tertiary structure (H bonds also 2ndary)
a) Numerous, but VERY easily broken. The more, the harder to break
b) Stronger, but VERY easily broken with any pH change
c) STRONGEST! Only formed when sulfur in R group. Only 2/20 human amino acids have sulfur though
What does the tertiary structure depend on?
The R groups - both the combination and elements. Very specific
If polypeptide has CHOCO in its R group, and another has COCO, why do they form different structures?
Because in the tertiary structure, bonds such as hydrogen bonds are formed between R groups. This is very specific, so altering the combination or - in this case - elements will completely change the outcome of the 3D protein it forms
What is quaternary structure?
When a protein is made from more than 1 type of polypeptide chain, e.g. having a prosthetic group. The same bonds as tertiary structure hold it together (H bonds, ionic bonds, disulfide bridges)
What is a prosthetic group? Give an example
A non-protein group. Haemoglobin contains iron, so has to go through quaternary structure
Describe how a peptide bond is formed between 2 amino acids to form a dipeptide. (2)
A hydrogen from the amine section of one amino acid will combine with the hydroxide of another amino acid’s carboxyl section. These form the water molecule lost during this condensation reaction. The amino acid residues left form a peptide bond, forming a dipeptide
What are primary peptides?
Polypeptides
