Biological molecules Flashcards
2 marks
Two proteins have the same number and type of amino acids but different tertiary box
structures.
Explain why.
- Different primary structure
- Forms ioninic/ disulfide/ hydrogen bonds in different places
2 marks
Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end.
- One amine group joins to a carboxyl group to form a peptide bond
- So in chain there is a free amine group at one end and a free carboxyl group at the other
4 marks
Describe how the structure of glycogen is related to its function.
- Helical so compact
- Polymer of glucose so easily hydrolysed
- Branched so more ends for faster hydrolysis
- Glucose polymer so provides respiratory substrate for energy release
- Insoluble so no osmotic effect
4 marks
Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein
- Glucose and galactose
- In a condensation reaction
- Joined by glycosidic bond
- Added to a polypeptide in golgi body
3 marks
How to test for non-reducing sugar
Heat with acid and neutralise
Heat with benedicts
If present red precipitate formed
3 marks
Differences between phospholipid and triglyceride
- 3 fatty acids rather than 2;
- 3 ester bonds rather than 2;
- No phosphate group;
Unsaturated fatty acids bonds
Double bonds present between carbon atoms
Unsaturated fatty acids cause bends/kinks in fatty acid tail
Presence of double bonds decreases number of hydrogens presnt in fatty acids
3 marks
A competitive inhibitor decreases the rate of an enzyme-controlled reaction.
Explain how.
- Inhibitor similar shape to substrate
- Binds to active site
- Less enzyme-substrate complex forming
3 marks
When bread becomes stale, the structure of some of the starch is changed. This changed starch is called retrograded starch.
Scientists have suggested retrograded starch is a competitive inhibitor of amylase in the small intestine.
Assuming the scientists are correct, suggest how eating stale bread could help to reduce weight gain.
- Less hydrolysis of starch
- To maltose
- Less absorption of glucose
4 marks
Give two reasons why glucose uptake by muscle cells increases significantly during exercise. Explain your answers
- Increased respiration;
- To provide more ATP for muscle contraction;
- (More glucose being used so) concentration gradient for glucose
- (Glucose enters by) facilitated diffusion;
Describe the structure of both a sucrose-transport protein and a glucose-transport protein?
The secondary structure is held by hydrogen bonds.
The tertiary structure allows the protein to be positioned spanning the whole cell membrane.
3 marks
Describe how he made a 1 in 10 dilution and then used this to make a 1 in 1000 dilution of the original liquid culture of bacteria
- 1/10 dilution is made by 1 part liquid culture, 9 parts of water
- Mix, repeat 2x
- 1 part of 1/10 dilution, 9 parts of water = 1/100 dilution
- 1 part of 1/100 dilution, 9 parts of water= 1/1000 dilution
4 marks
Describe how to make a temporary mount
- Add drop of water to glass slide
- Obtain thin section of specimen and place on glass slide
- Stain with iodine
- Lower cover slip using mounted needle
5 marks
Describe the structure of DNA.
- Polymer of nucleotides
- Each nucleotide formed from deoxyribose, a phosphate group and a nitrogenous base
- Phosphodiester bonds between nucleotides
- Double helix
- Hydrogen bonds between complementary base pairings= adenine, thymine and cytosine, guanine
4 marks
Explain how ATP is a suitable energy source for cells to use
- Immediate source of energy/ releases energy immediately
- Little energy lost as heat
- Doesnt leave cells
- Phosphorylates other compounds, making them more reactive
