2.4 Proteins Flashcards
Proteins have a very wide range of functions in living organisms.
What are proteins composed of
polypeptides -> composed of amino acids
how many universal amino acids are there
20
What are polypeptides
long chains of joined amino acids.
Distinct chemical properties, which affect fold and function.
Peptide bonds - link 2 amino acids to form a polypeptide
covalent chemical bond linking two consecutive alpha-amino acids from C1 of one alpha-amino acid and N2 of another, along a peptide or protein chain.
What composes an amino acid
amine group (NH2) + HC R-group + Carboxyl group (OHC=O)
Primary structure (order of the amino acid sequence)
determines how the chain folds due to the chemical properties of the variable group. The order of amino acids determines all subsequent levels of protein folding.
Secondary structure (stable configuration)
This is the result of the hydrogen bonds of non-adjacent amine and carboxyl groups.
Coil/spiral arrangement = alpha helices
Directionally oriented staggered strand conformation = beta-pleated sheets.
Random coil = no secondary structure exists.
The tertiary structure (3D config.)
Overall 3D configuration is determined by the variable chain - the interactions are between hydrogen bonds, disulphide bridges, ionic interactions, polar association, etc.
Affinity/repulsion is determined by the overall shape of the polypeptide chain and the position of specific amino acids within the sequence.
Quaternary Structure (multiple protein structures)
Found in proteins that consist of more than one polypeptide chain linked together, including inorganic prosthetic groups.
E.g. haemoglobin (carries oxygen) > composed of iron-containing haeme groups (prosthetic groups responsible for binding oxygen
Denaturation
Structural change in a protein that results in the loss of its biological properties. Protein folds determine function - change or abrogation of the tertiary structure alter activity.
Temperature
Disrupt the hydrogen bonds that hold the protein together. Bonds are broken, the protein will begin to unfold and lose its capacity to function as intended
pH
Amino acids are zwitterions, neutral molecules possessing both negatively (COO–) and positively (NH3+) charged regions. Alters charge - protein solubility & shape
zwitterions
neutral molecules possessing both negatively and positively charged regions
Stages of DNA sequencing
- Transcription
2. Translation
Describe transcription
DNA template to make an mRNA transcript (occurs w/in nucleus)
Describe Translation
instructions of mRNA transcript to link amino acids together (ribosome)
What is the proteome
It is the totality of proteins expressed within a cell/tissue/organism at a certain time. It is significantly larger than the number of genes in an individual.
Protein functions (SHITS ME)
STRUCTURE HORMONES IMMUNITY TRANSPORT SENSATION MOVEMENT ENZYMES
Protein function: STRUCTURE
collagen (component of the connective tissue of animals)
spider silk (fibre spun by spiders).
Protein function: HORMONES
insulin (produced by the pancreas = triggers a reduction in blood glucose levels)
glucagon (pancreas = triggers an increase in blood glucose levels)
Protein function: IMMUNITY
immunoglobulins (Antibodies produced by plasma cells - targets specific antigens).
Protein function: TRANSPORT
haemoglobin (found in red blood cells that is responsible for the transport of oxygen)
cytochrome (located in the mitochondria and involved in the electron transport chain).
Protein function: SENSATION
rhodopsin (pigment - photoreceptor cells of the retina, detection of light).
Protein function: MOVEMENT
actin (thin filaments involved in the contraction of muscle fibres)
myosin (thick filaments involved in the contraction of muscle fibres).
Protein function: ENZYMES
rubisco (enzyme involved in the light independent stage of photosynthesis)
catalase (catalyses the decomposition of hydrogen peroxide to water and oxygen).
