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Biology: ch2 (exam questions)

Terms in this set (40)

1) Polar molecule - acts as a universal solvent.

2) Universal solvent - reactions occur faster in water.

3) Reactive - takes place in hydrolysis/condensation
Give 2 properties of water that are important in the cytoplasm of cells. For each property explain its importance in the cytoplasm. (4)
1) Na^2+
2) H+
3) PO^4-
Name all the ions in the specification.
1) Both move down concentration gradient.

2) Both move through protein channels in membrane.

3) Ions move against a concentration gradient by active transport whereas water moves down a concentration gradient by facilitated diffusion.
Compare and contrast the processes by which water and inorganic ions enter cells.
ADP + Pi -> ATP + H2O
Write the equation for the reaction catalysed by ATP synthase.
1) Releases relatively small amount of energy/little energy is lost as heat.

2) Releases energy instantaneously.

3) Phosphorylates other compounds, making them more reactive.

4) Can be rapidly re-synthesised.

5) It is not lost/does not leave cells.
Give 2 ways in which ATP is a suitable energy source for cells to use.
1) From ADP and phosphate.

2) By ATP synthase.

3) During respiration/photosynthesis.
Describe how ATP is resynthesised in cells.
1) To provide energy for other reactions.

2) To add phosphate to other substances and make them more reactive/change their shape.
Give 2 ways in which the hydrolysis of ATP is used in cells.
1) starch

2) glycogen

3) deoxyribose
Which substances contain only the elements carbon, hydrogen and oxygen (out of starch, glycogen, deoxyribose and DNA helicase)?
1) Holds chains/cellulose molecules together/forms cross links between chains/forms microfibrils, providing strength/rigidity.

2) Hydrogen bonds strong in large numbers.
Hydrogen bonds are important in cellulose molecules. Explain why.
1) hydrogen bonds are present in DNA and tRNA.

2) hydrogen bonds are not present in mRNA.
Are hydrogen bonds present in DNA, mRNA and tRNA?
Base
Which part of the DNA molecule contains hydrogen?
viral DNA single-stranded/not double-stranded.
How is the structure of DNA of a virus different to the DNA of bacterium and humans?
Nucleotide.
What are the monomers which nucleic acids are made up of?
Molecule made up of many similar molecules/monomers.
What is meant by a polymer?
Purple.
When protein is tested with biuret reagent - what colour does it go?
1) Each strand copied/acts as a template.

2) DNA one new strand and one parent strand.
Explain why replication of DNA is described as semi-conservative.
1) 2 strand therefore semi-conservative replication is possible.

2) Base pairing/hydrogen bonds hold the strands together.

3) Hydrogen bonds weak/easily broken - allow the strands to separate.

4) Bases exposed/ act as a template - so can be copied.

5) A with C, T with G/complementary copy.
Describe and explain how the structure of DNA results in accurate replication.
1) chromosomes shorten/thicken.

2) two identical chromatids/copies/strands due to DNA replication.

3) Chromosomes/chromatids move to equator.

4) Attach to individual spindle fibres.

5) Spindle fibres contract/centromeres divide/

6) Sister chromatids move to opposite poles.

7) Each pole receives all genetic information/identical copies of each chromosome.

8) Nuclear envelope forms around each group of chromosomes/chromatids at each pole.
Describe the behaviour of chromosomes during mitosis and explain how this results in the production of two genetically identical cells.
1) tRNA 'clover leaf' shape.

2) tRNA standard length.

3) tRNA has an amino acid binding site.

4) tRNA has anticodon

5) tRNA has hydrogen bonds.
Give 2 ways in which the structure of tRNA differs from the structure of a mRNA molecule.
1) Hydrogen bonds broken

2) Semi-conservative replication.

3) Nucleotides line up/complementary base pairing/A-T and C-G.

4) DNA polymerase.
Explain how DNA replicates (4)
1) deletion causes frame shift / alters base sequence (from point of mutation);

2) changes many amino acids / sequence of amino acids (from this point);

3) substitution alters one codon / triplet / one amino acid altered / code
degenerate / same amino acid coded for;
Explain why a mutation involving the deletion of a base may have a greater effect than
one involving substitution of one base for another (3).
determines (sequence of) amino acids / specific protein produced / mRNA formation;
The sequence of bases on one strand of DNA is important for protein synthesis.
What is its role? (1)
1) stability

2) protects bases

3) replication;
Give 3 advantages of DNA having 2 strands.
1) DNA is double stranded, RNA is single stranded;

2) DNA has thymine present, RNA has Uracil present;

3) DNA is larger/heavier/longer, RNA is smaller/lighter/shorter;

4) DNA has a deoxyribose sugar, RNA has a ribose sugar;

5) DNA stays in the nucleus, RNA leaves the nucleus;
Give two differences between DNA and RNA. (2) (5 reasons given).
1) Carries coded information about the sequence of amino acids;

2) Copied from DNA/gene;

3) Code is in sequence of bases / triplet / three bases / a codon codes
for one amino acid;

4) Moves out of nucleus/goes into cytoplasm;

5) To ribosomes
Describe the part played by RNA in protein synthesis. (3)
1) DNA is a large molecule, and RNA is smaller.

2) DNA is double stranded, whereas RNA is single stranded.

3) DNA contains thymine, whereas RNA contains uracil.

4) DNA contains deoxyribose, whereas RNA contains ribose.
Give 2 differences in structure between DNA and RNA. (2) - (4 things).
1) Base sequence in DNA/gene.

2) Determines sequence of amino acids.

3) By determining base sequence on mRNA.

4) Code is a triplet code/3 bases code for an amino acid.
Explain how a gene codes for a protein. (2)
1) Pairs of chromosomes/2 chromosomes.

2) With genes for same features / with same genes;

3) At same loci.
What are homologous chromosomes? (2)
1) Releases energy in small / manageable amounts;

2) (Broken down) in a one step / single bond broken immediate energy
compound / makes energy available rapidly;

3) Phosphorylates / adds phosphate makes (phosphorylated substances)
more reactive / lowers activation energy;

4) Reformed / made again;
ATP is useful in many biological processes. Explain why. (4)
1) DNA has antiparallel strands.

2) shape of the nucleotides is different.

3) Enzymes have active sites with specific shape;

4) Only substrates with complementary shape / only the 3' end can bind
with active site of enzyme / active site of DNA polymerase.
The arrows in Figure 2 show the directions in which each new DNA strand is being
produced.
Use Figure 1, Figure 2 and your knowledge of enzyme action to explain why the
arrows point in opposite directions. (4)
1) Semi-conservative replication;

2) Complementary pairing;

3) Hydrogen bonding (of
bases/nucleotides);

4) Condensation/described of nucleotides;

5) DNA polymerase
involved;
Describe how, after the parent DNA strands separated, the second strand of DNA in
region Y was formed. (3)
1) Reference to DNA polymerase;

2) (Which is) specific;

3) Only complementary with / binds to 5' end (of strand);

4) Shapes of 5' end and 3' end are different
During replication, the two DNA strands separate and each acts as a template for
the production of a new strand. As new DNA strands are produced, nucleotides can
only be added in the 5' to 3' direction.
Use the figure in part (a) and your knowledge of enzyme action and DNA replication
to explain why new nucleotides can only be added in a 5' to 3' direction. (4)
Joins nucleotides (to form new strand).
Describe the role of DNA polymerase in DNA replication. (1)
1) Circular / non-linear (DNA);

2) Not (associated) with proteins / histones;

3) No introns / no non-coding DNA.
Other than being smaller, give two ways in which prokaryotic DNA is different
from eukaryotic DNA. (2)
1) Have different genes;

2) (Sobases / triplets) are in a different sequence / order;

3) (So) different amino acid (sequence / coded for) / different protein /
different polypeptide / different enzyme.
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)
1) A does not equal T / G does not equal C;

2) (So) no base pairing;

3) (So) DNA is not double stranded / is single stranded.
The DNA of the virus is different from that of other organisms. Use the table
above and your knowledge of DNA to suggest what this difference is. Explain
your answer. (3)
1) each strand copied / acts as a template;

2) (daughter) DNA one new strand and one original / parent strand;
Explain why the replication of DNA is described as semi-conservative. (2)
1) Separates / unwinds / unzips strands / helix / breaks H-bonds;

2) (So) nucleotides can attach / are attracted / strands can act as
templates;
DNA helicase is important in DNA replication. Explain why. (2)
1)From ADP and phosphate;

2) By ATP synthase;

3) During respiration/photosynthesis;
Describe how ATP is resynthesised in cells. (2)
1) To provide energy for other
reactions/named process;

2) To add phosphate to other
substances and make them more
reactive/change their shape;
Give two ways in which the hydrolysis of ATP is used in cells. (2)
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