Biological molecules tonight Flashcards
1.4 proteins, 1.4.2 enzymes, 1.6 ATP, 1.2 Carbs, 1.1 intro, 1.3 lipids, ions, 1.7 water, 1.5.1 DNa and RNA
Describe how a peptide bond is formed between 2 amino acids to form a dipeptide.
amino group and carboxylic group
Condensation reaction
Water removed
The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how.
hydrogen bonds
Between amino group and carboxylic group
Forming alpha helix or beta pleated sheets
two proteins have the same number and type of amino acids but different tertiary structures. Explain why
- different primary sequence of AA
- R group bond form in different places
At what level of protein structure do hydrophobic interaction occurs?
Tertiary, Quaternary
What does a haemoglobin molecule contain?
4 polypeptide chains
with 1 haem group
Describe one similarity and one difference between the induced fit model of enzyme activity and the lock and key model.
sim
- substrate binds to AS
- enzyme substrate complexes formed
diff
As changes shape, but doesn’t change in lock and key
AS not complimentary to substrate with induced fit, but is complementary in lock and key
The scientists expressed their results as Percentage of lipid in plasma membrane by mass. Explain how they would find these values.
mass of each lipid/ mass of all lipids x 100
ester bond
between carbon and oxygen
Name the type of reaction that joins monosaccharides together.
condensation reaction
Which of the fatty acids, X or Y, in the figure above is unsaturated
Contains double bond between (adjacent) carbon atoms in hydrocarbon chain.
what is the significance of quaternary structure in proteins?
holds together multiple polypeptide chains
and other molecules necessary for protein function
therefore contributing to the overall structure and function of proteins
What are the two common secondary structure found in proteins and what causes their formation
alpha helix and beta pleated sheets
formed due to hydrogen bonding between carboxyl and amino residue of polypeptide chain
Describe the structural nature of enzymes
globular proteins
specific tertiary structure
complementary to substrates
substrates bind to active site of enzymes
Explain the tertiary structure of proteins and the forces involved in its formation
Folding of polypeptide into specific complex shape
due to IMFs between R group
e.g. Hydrogen bonds, ionic bonds, disulfide bridge and London forces
Explain the relationship between substate concentration and enzyme activity
increase substrate conc increases rate of reaction
as more enzyme substrate collisions
there is a max rate when all active sites are occupied
enzymes saturation
rate of reaction calculation
change in conc or substrate/ time
what type of bond is formed in condensation reaction to create a polypeptide
peptide bond
between amine group of one AA and carboxyl group
releasing water
What is the monomer of proteins, and how many naturally occurring variations exist
amino acid
20 variations each distinguished by unique R group
Difference between competitive and non competitive inhibitors
competitive - bind the active site of enzymes, blocking substrate form binding
Non competitive inhibitors - bind to different site on enzyme - causing a conformational change that alters the shape of the active site
what impact does Ph have on enzyme activity
change ion Ph away from optimum can disrupt ionic forces and hydrogen bonds
causing enzymes tertiary structure to deform
This alters the shape of the active site
reducing its complementarity to the substrate and decreasing the reaction rate
How are polypeptides broken apart and what is required for this reaction
broken apart by hydrolysis reactions
requires the addition of water to break the peptide bonds
How is the presence of proteins tested using buret test, and what constitutes a positive result
adding copper sulphate and sodium hydroxide to a solution
+ve - blue –> purple
shows presence of peptide bond
How does temperature affect the rate of enzyme controlled reactions?
increasing temp initially increases rate of reaction by providing more kinetic energy for successful enzyme substrate collision
optim temp - enzymes denature
decreasing the rate as the active site loses its complementary shape
Differentiate between globular and fibrous proteins structure providing examples of each
globular proteins have specific shape and involved in functions like enzyme catalysis and molecular signalling
fibrous proteins are structural and provide strength and flexibility
e.go collegen and keratin
what is the primary function of enzymes in biological systems?
enzymes catalyse biochemical reactions
without increasing the rate of reaction without being consumed in the process
Discuss the induced fit model of enzyme substrate interaction
substrates initially collide with enzymes active site and form an enzyme substrate complex. This interaction induces slight changes in shape of active site making it more complementary to the substrate, which facilitates the reaction
what is the primary structure of a protein and what role does it play in protein shape?
refers to sequence of amino acids in a protein
joined by peptide bonds
controls the overall protein shape and function
How does enzyme concentration affect reaction rate?
increasing enzyme conc increase rate as there are more enzymes available to catalyse substrate molecules are instantly converted to products
Explain how enzymes reduce the activation energy of reactions
enzymes lower the activation energy required to initiate a reaction by binding to substrate at their active site, straining the bonds in the substrates and facilitating their conversion into products
what is the primary structure of a protein and what role does it play in protein shape?
the primary structure refers to the sequence of amino acids in a protein,
joined by peptide bonds
controls the overall protein shape and function
What is the difference between a saturated and unsaturated fatty acid
saturated no c=c double bonds
unsaturated one or more c=c double bonds
(a) In humans, the enzyme maltase breaks down maltose to glucose.
This takes place at normal body temperature.
Explain why maltase:
* only breaks down maltose
* allows this reaction to take place at normal body temperature.
- Tertiary structure / 3D shape of enzyme (means);
2. Active site complementary to maltose / substrate / maltose fits into active site / active site and substrate fit like a lock and key; 3. Description of induced fit; 4. Enzyme is a catalyst / lowers activation energy / energy required for reaction;
- By forming enzyme-substrate complex;
Scientists have investigated the effects of competitive and non-competitive inhibitors of the enzyme maltase.
Describe competitive and non-competitive inhibition of an enzyme.
- Inhibitors reduce binding of enzyme to substrate / prevent formation of ES complex;
2. Inhibitor similar shape (idea) to substrate; 3. (Binds) in to active site (of enzyme); Accept allows max rate of reaction to be reached / max product will eventually be formed 4. (Inhibition) can be overcome by more substrate; (Non-competitive inhibition), 5. Inhibitor binds to site on enzyme other than active site; 6. Prevents formation of active site / changes (shape of) active site;
- Cannot be overcome by adding more substrate;
Describe how A quaternary protein is formed from its monomers
Amino acid joined by peptide bonds
- condensation reactions
- secondary structure formed by hydrogen bonding
- teritary structure is formed by interactions between R groups
- quaternary strcutre contains more than 1 polypeptide
- Quaternary strcutre is formed by interactions/ bonds between polypeptides
Describe how the structure of a protein depends on the amino acids it contains.
- Structure is determined by (relative) position of amino acid/R group/interactions;
2. Primary structure is sequence/order of amino acids; 3. Secondary structure formed by hydrogen bonding (between amino acids); Accept alpha helix/β-pleated sheet for ‘secondary structure’ 4. Tertiary structure formed by interactions (between R groups); 5. Creates active site in enzymes OR Creates complementary/specific shapes in antibodies/carrier proteins/receptor (molecules);
Describe the structure of proteins.
- Polymer of amino acids;
2. Joined by peptide bonds;
3. Formed by condensation;
4. Primary structure is order of amino acids;
5. Secondary structure is folding of polypeptide chain due to hydrogen bonding;
Accept alpha helix / pleated sheet
6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide bonds;
7. Quaternary structure is two or more polypeptide chains.
The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how.
Hydrogen bonds form amino acids between NH and c=o group
beta pleased sheet
Two proteins have the same number and type of amino acids but different tertiary structures. Explain why.
Different sequence of Amino acids
different primary structures
Form ionic/ hydrogen/ disulphide bonds in different places
Name the chemical element found in all amino acids that is not found in triglycerides.
nitrogen
Aspartic acid and pralinee are both amino acids. Describe how two amino acids differ from one another.
different R groups