Unit 1 =) Flashcards
Similarities between the structures of starch and cellulose
- Polymers
- Contain glucose (C, H, O)
- Glycosidic bonds
- Have 1-4 links
- Hydrogen bonds (within structure)
- Joined by condensation
Differences between starch and cellulose
Starch:
1. α glucose
2. branched (not straight)
3. 1,6 bonds
4. glucoses same way up
5. no H-bonds between molecules
6. no fibres/ fibrils
Explain how cellulose molecules are adapted for their function in plant cells. (3)
- Long, straight chains
- Linked tgt by many hydrogen bonds -> fibrils
- Provide strength (cell wall)
Explain how a non-competitive inhibitor would decrease the rate of reaction catalysed by an enzyme. (3)
- binds to sites other than active site
- causes change in shape of active site
- substrate no longer able to bind to a.s.
E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell
maintains a constant shape. Explain why. (2)
- Cell unable to change shape;
- (Because) cell has a cell wall;
- (Wall is) rigid / made of peptidoglycan / murein.
Hydrogen bonds are important in cellulose molecules. Explain why. (2)
- holds chains tgt
- forms crosslinks betw chains
- forms microfibrils
- Hydrogen bonds strong in large numbers
What is meant by the tertiary structure of a protein? (1)
The way the whole protein is folded.
Explain how heating an enzyme results in it being denatured. (2)
↑ ke
Bonds holding tertiary structure break
Describe the role of enzymes of the digestive system in the complete breakdown of starch. (5)
- Amylase
- Starch –> Maltose
- Maltase
- Maltose –> Glucose
- Hydrolysis
- Breaking of glycosidic bond
Explain why each new DNA strand is synthesised in opposite directions. (4)
1.DNA has antiparallel strands
2. Shape of the nucleotides is different
3. Enzymes have active sites w/ specific shapes
4. Only substrates w/ complementary shapes (3’ end) can bind to active site of DNA polymerase
Cholesterol increases the stability of plasma membranes, by making them less flexible.
Suggest one advantage of red blood cells containing more cholesterol than cells lining the ileum. (1)
- rbc free in blood (not supported by other cells)
- cholesterol helps maintain shape
The higher the altitude, the lower the mean temperature.
Explain how the lower temperature at high altitude reduces growth of plants. (4)
- ⬇️ enzyme activity
- ⬇️ rate of photosynthesis so⬇️ carbohydrates formed
- ⬇️ respiration
- ⬇️ rate of nutrient uptake
Give differences between DNA and RNA.
- double stranded vs single stranded
- thymine vs uracil
- longer vs shorter
- deoxyribose vs ribose
- stays in nucleus vs leaves
A polypeptide had 51 amino acids in its primary structure.
The actual number of bases in the gene for this polypeptide is more than the minimum number of DNA bases required to code for the amino acids. Explain why. (1)
Some regions of the gene are non-coding (introns).
A student carried out an investigation into the mass of product formed in an enzyme-controlled reaction at three different temperatures. Only the temperature was different for each experiment.
Explain why the curves for 27 °C and 37 °C level out at the same value. (2)
- All substrate changed into product
- Same amount of product formed as same initial conc. of substrate
What is an enzyme? (2)
- Protein
- Catalyst
- for a specific substrate
- Lowers activation energy
ATP is an energy source used in many cell processes.
Give two ways in which ATP is a suitable energy source for cells to use. (2)
- Immediate energy source
- Releases relatively small/ manageable amounts of energy
- Phosphorylates other compounds, making them more reactive
- Rapidly resynthesised
- x leave cells (x lost)
A precipitate is produced in a positive result for reducing sugar in a
Benedict’s test.
A precipitate is solid matter suspended in solution.
A student carried out the Benedict’s test. Suggest a method, other than
using a colorimeter, that this student could use to measure the quantity of
reducing sugar in a solution. (2)
- filter and dry
- find mass
Use of a colorimeter in this investigation would improve the repeatability of
the student’s results. (instead of determining which solution is darker in colour in a Benedict’s test)
Give one reason why. (1)
- quantitative
- standardises method
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. (3)
- ↓ HYDROLYSIS of starch
- to maltose
- ↓ absorption of glucose
The sequence of bases on one strand of DNA is important for protein synthesis.
What is its role? (1)
- determines amino acids
- specific protein produced
- mRNA formation
Give one advantage of DNA molecules having two strands. (1)
- stability
- protects bases
- replication
Describe how a saturated fatty acid differs in molecular structure from an unsaturated fatty acid. (2)
- absence of double bond
- in hydrocarbon chain
- saturated w/ H
Where is amylase produced?
Pancreas –> maltose
Where is maltase produced?
EPITHELIUM of small intestine –> glucose
What is a polymer?
Molecule made up of many identical monomers.
Explain why a buffer solution is added to an enzyme-substrate mixture. (2)
- constant pH
- change in pH will slow rate of reaction/ denature enzyme
Explain how sulphur-containing amino acids help to give keratin (protein) molecules their characteristic strength. (2)
- disulphide bridges (chemical bonds) formed between sulphur-containing groups
- bind chains to each other
Explain why differences in primary structure result in keratins with different properties. (2)
- diff. sequences of a.a.
- bonds in diff. places so give diff. shapes
Humans and grasshoppers have very similar percentages of each base in their DNA but they are very different organisms.
Use your knowledge of DNA structure and function to explain how this is possible. (2)
- diff. genes
- bases in diff. seq
- diff. seq of a.a. –> diff. proteins
HSV infects nerve cells in the face (line 1).
Explain why it infects only nerve cells. (3)
- antigens outside of virus
- shape complementary to receptors in membrane of cells
- found only on membrane of nerve cells
Explain what it means when a virus is described as inactive inside the body. (2)
- no more cells infected
- ∵ virus X replicating