| How many amino acids are there and where are they made? | 20 different amino acids in polypeptides synthesised on ribosomes by translation |
| How do the different amino acids differ so much? (in structure) | the variable side chain (R) has distinct chemical properties (eg: charged)
the protein folds and works differently according to its position in the polypeptide chain |
| How are amino acids joined together? | covalently linked by PEPTIDE BONDS which are formed by condensation reactions = water molecules formed as a byproduct |
| condensation reaction diagram =forms peptide bond | OH from carboxyl group and H from amine group in second amino acid is removed to form H2O |
| How can polypeptide chains be broken down? | hydrolysis reactions which needs water to reverse the process |
| What is the primary structure of proteins? | order of the amino acid sequence in a polypeptide sequence = determined the way the chain will fold
different sequences will fold differently because of the chemical properties of the R variable |
| What is the secondary structure of proteins? (A + B) | 2 stable configurations formed from amino acid sequences
Alpha Helices = amino acids folds into a coil
Beta-Pleated Sheets = directionally oriented staggered strand
from hydrogen bonds between non-adjacent amine and carboxyl groups
Otherwise the primary structure will form a random coil |
| How is the tertiary structure formed? | 3D protein is determined by the interactions between the variable side chains =
H bonds, disulphide bridges , ionic interactions, polar associations |
| What determines the overall shape of the polypeptide chain? | attraction or repulsion of side chains which are determined by the position of specific amino acids within a sequence
primaary structure determines all the following levels of protein folding |
| How is a quaternary structure formed? | found in proteins that are made of more than one polypeptide chain linked together
if they include inorganic prosthetic groups
most proteins are single polypeptide chains |
| What is an example of a quaternary structure protein? (3) | haemoglobin which carries O2 in red blood cells
made of 4 polypeptide chains (2 alpha and 2 beta)
made of iron containing haeme groups (prosthetic groups ) = helps bind oxygen |
| What is denaturation in proteins? (3) | structural change that causes a loss of its biological properties
Because the way a protein folds determines its function
any change = alters activity |
| What causes denaturation? (2) | pH
Temperature |
| How does temperature cause denaturation? (2) | high thermal energy breaks the H bonds holding the protein together
protein unfolds and loses function
denaturing temp usually varies but human proteins work best at the body temp of (37 degrees) |
| How does pH cause denaturation? | Amino acids are zwitterions (neutral molecules with both negative (COO-) and positive (NH3+) charged regions
changing pH = changes the protein charge = changes protein solubility and shape
optimal pH for a protein depends on the environment where it functions |
| What is a gene? | a DNA sequence that encodes a polypeptide sequence |
| How is a gene sequence converted into a polypeptide chain? (2 processes) | transcription - makes mRNA transcript from DNA template in nucleus
translation - uses instructions from mRNA transcript to link amino acids together in ribosome |
| variations to genes encoding for polypeptide chains? (3) | could be alternatively spliced to make many polypeptide variants
genes encoding for tRNA are transcripted but not translated
genes could be mutated (base sequence changes) = different polypeptide sequence |
| What are proteomes? | total number of proteins expressed in a cell, tissue or organism at a certain time
unique to the individual as protein expressions are determined by the person's gnees |
| Why are proteomes always larger than the number of genes an individual has? | gene sequences could be alternatively spliced after transcription = makes multiple protein variants
proteins can be modified after translation = causes more variations |
| What are the functions of proteins? (SHITS ME) | Structure
Hormones
Immunity
Transport
Sensation
Movement
Enzymes |
| What are examples of protein used as structure? | collagen: connective tissue in animals
spider silk: fiber to make webs |
| What are examples of protein used as hormones? | insulin: made in pancreas to trigger a reduction of blood glucose levels
glucagon: made in pancreas to increase blood glucose levels |
| What are examples of protein used as immunity? | immunoglobulins: antibodies made in plasma cells to target specific antigens |
| What are examples of protein used as transport? | haemoglobin: in red blood cells to transport oxygen
cytochrome: in mitochondria used in the electron transport chain |
| What are examples of protein used as sensation? | rhodopsin: pigment in photoreceptor cell of the retina to detect light |
| What are examples of protein used as movement? | actin: thin filaments to contract muscle fibres
myosin: thick filaments to contract muscle fibres |
| What are examples of protein used as enzymes? | Rubisco: used in the light dependent stage of photosynthesis |
| Draw the structure of an amino acid | amine group (NH2)
Carboxylic acid group (COOH)
hydrogen atom (H)
Variable Side Chain (R) |
| What are proteins made out of? | long chains of recurring monomers called amino acids |
