Proteins And Enzymes Flashcards
What is the function of haemoglobin
Allows oxygen to bind and be transported around the organism
What is the function of an antibody
Binds to specific antigen, used in all immune responses against pathogen
Function of enzyme
Reduces activation energy within a metabolic reaction
Function of actin and myosin
Structural proteins involved in muscle contraction
Function of keratin
Structural proteins found in nails, talons etc
Function of collagen
Structural proteins found in tendons
What are proteins made of
Monomers of amino acids
Draw the structure of an amino acid
H. H O
I. I. II
H-N-C-C-OH
I
R
Describe the function of an enzyme and how it becomes denatured with temperature and pH
Specific shape of the protein is essential to its function
Proteins only denature at high temperatures and changes to Ph
Increasing temperature increases the kinetic energy of the molecules making them vibrate , this breaks the weak hydrogen bonds in the secondary and tertiary structure
Changing PH breaks ionic bonds
Desaturation is permanent
Examples of globular proteins
Transport proteins such as haemoglobin
Enzymes such as amylase
Hormones such as insulin
Structural proteins example
Keratin- hair
Collagen- connective tissue
Elastin- connective tissue
Define globular protein
Spherical shape and are soluble in water, they are highly unstable and undergo denaturation catalysed by slight changes in
Describe the structure of proteins
Polymer of amino acids
Joined by peptide bonds
Formed by condensation reaction
Primary structure is order and sequence of amino acids
Secondary structure is the folding of polypeptide chain due to weak hydrogen bonds forming alpha helixes and beta pleated sheets
Tertiary structure is 3D folding of polypeptide chain held by ionic and hydrogen bonds and disulphide bridges.
Quaternary structure is two or more polypeptide chains joined together
When a pathogen causes an infection, plasma cells secrete antibodies that destroy pathogen
Antigens are specific shape/tertiary structure
Antibody is complementary to antigen so binds to form antibody-antigen complex
Variable regions on antibodies are specific shape
Antigens bind
Biuret test
Changes to from blue to purple if protein is present
Define activation energy and describe how enzymes lower this
The minimum energy required for a successful chemical reaction
They lower activation energy by stressing and distorting the bonds in the substrate during the formation of an enzyme substrate complex
Stages of the lock and key model
The active site is rigid and doesn’t change shape
The substrate binds to the enzymes active site
The substrate fits exactly as they are complementary
Products are formed and no longer fit the active site so are released
The enzyme is free to partake in another reaction
Describe the induced fit model
Active site not complementary
Active site changes shape to form ESC
Stressing and distorting bonds
Suggest why a protein can be the substrate for 2 different enzymes
Different parts of the protein have different amino acid sequences so are a different shape
Each enzyme active site is a specific shape and complementary to a different part of the protein
Define the term rate
Change in Y per unit time
Define optimum temperature
The maximum energy that can be supplied to the molecules before hydrogen and ionic bonds start to break
Effects of temperature on enzymes
Increase in kinetic energy, more likely to successfully collide and react- rate of reaction increases as more substrate complexes are being formed.
Beyond optimum, kinetic energy is too great which causes the hydrogen bonds and ionic bonds between R groups to break, causing a change in the specific tertiary structure
No longer complementary so can’t bind to form ESC- enzyme becomes denatured
What exactly is pH and what happens to bonds when it changes
A measure of hydrogen ion concentration
If changed the charge on the R groups of amino acids are altered and ionic and hydrogen bonds are broken, altering tertiary structure
What scale is pH recorded in and why
Log- the concentration of H+ ions is too large
Explain a substrate concentration graph
As the substrate concentration increases, the rate of reaction increases and then plateaus
When substrate concentration is low there is a low rate of reaction due to fewer collisions and therefore fewer enzyme-substrate complexes formed per second. The substrate becomes the limiting factor. Plateaus as all binding sites are saturated so the enzyme concentration is now the limiting factor
What is the effect of increasing substrate conc on the rate of an enzyme controlled reaction
Increases then plateaus as all active sites are saturated
Competitive inhibitors
Have similar shape to substrate
Bind to the active site and prevent the substrate from binding temporarily
Fewer ESC form per second
Reduce the rate of reaction so fewer products are formed per second
Can be overcome by increasing substrate concentration
Non-competitive inhibitors
Bind to the allosteric site, causing an alteration to the tertiary structure and active site so substrate is no longer complementary and bind
Fewer ESC formed
Decreased rate of reaction
Can’t be overcome
An enzyme controlled reaction is inhibited by substance X
Suggest a simple way in which you could tell whether substance X is acting as a competitive or non-competitive inhibitor
Calculate the rate of reaction- if it plateaus at a low rate it is a non-competitive inhibitor, if increases to maximum- competitive
