Biological Molecules Flashcards
Explain why monitoring pH of mixture could show whether the milk contained lipids (2)
- Hydrolysis of lipids produce fatty acids
- Which lowers pH
Describe biochemical tests to confirm the precense of amylase?
- Add Biuret and becomes lilac
- Add starch, test for reducing sugar
When writing a null hypothesis, what is said?
X has no effect on Y
Explain why biologist chose to examine 200 cells?
So is a representative sample
Describe how a scientist could have used the temporary mounts of leaves to determine mean number of choloplasts in mesophyll cells of a leaf? (3)
- Select large number of cells
- Count all cells in field of view + count number of chloroplasts
- Divide chloroplasts by number of cells
Describe how temporary mounts of plant tissue are made? (4)
- Add a drop of water to slide
- Add thin plant tissue with drop of stain
- Macerate using mounting needle
- Add coverslip and remove excess
Explain why buffer solutions are used?
To maintain a stble pH throughout practical so optimum RoR
What does a non-competitive inhibitor do? (4)
- Bonds to enzyme away from active site (allosteric site)
- Causes conformational change of shape of active site so substrate can’t bind
- Fewer ESC form
- RoR decreases
What does competitive inhibitor do? (4)
How can this be overcome?
- Inhibitor has similar shape to substrate
- They bind to enzyme + prevent substrate from binding temporarily
- Fewer ESC form
- RoR decreases
Increasing substrate conc.
What’s the tertiary structure of a protein?
- Further folding determined by R group into 3D shape
- With hydrogen, ionic + disulphide bonds
Structure of an amino acid?
Describe structure of proteins? (5)
1) Polymer of amino acids, which are joined by peptide bonds by condensation reaction
2) Primary - Order + sequence of amino acids
3) Secondary - Folding of polypeptide chain due to hydrogen bonding forming a alpha helix/ beta pleated sheet
4) Tertiary - 3D folding due to hydrogen, ionic + disulphide bonds
5) Quaternary - 2 or more polypeptides joined together
Name 6 proteins
Haemoglobin
Antibody
Enzymes
Actin + Myosin —–> involved in muscle contraction
Keratin
Collagen
How does pH affect enzyme activity? (5)
- Charge on R group is altered
- Weak hydrogen/ionic bonds break
- Active site no longer complimentary
- Less ESC form
- RoR decreases + enzyme denatures
How does temperature affect enzyme activity?Increases/Decreases?
Temp increases - KE increases, more successful collisions, RoR increases because more ESC are formed
Temp decreases - KE decreases, weak hydrogen/ionic bonds break, changes tertiary structure so changes active site, no longer complimentary so less ESC are formed
What’s the induced fit model?
Active site isn’t complimentary so changes shape to bind with substrate
Lowers activation energy
Returns to original shape
Sucrase doesn’t hydrolyse lactose - why?
- Lactose has a different shape
- So doesn’t bind to active site of sucrase
- Active site + substrate aren’t complimentary
- No enzyme-substrate complex forms
How does active site of an enzyme increase the rate of reaction?
- Lowers the activation energy
- So induced fit causes active site to change shape
- By stressing + weakening bonds to form an enzyme-substrate complex
Why do proteins denature at:
1) High temperatures?
2) Changes in pH?
1) Increasing temperature, increases kinetic energy which breaks the weak hydrogen bonds in secondary + tertiary structure
2) “ “ breaks the ionic bonds between the R groups in tertiary structure
Test for lipid?
- Add ethanol
- Shake
- Add water
- Shake
- If present then white emulsion
Structure of phospholipid?
Formula for fatty acids?
Difference between saturated + unsaturated?
Saturated - No double bond
Function of lipids? (2)
Conduct heat slowly - good insulator
Stored around organs to protect
Where are these found?
- Triglyceride
- Phospholipid
Food (storage molecule)
Helps to form cell membrane
