Exam questions Flashcards
(70 cards)
1
Q
Why are viruses acellular?
A
- Don’t have a cell membrane
- Not made of cells
2
Q
Why are viruses non-living?
A
- Can’t independently respire/replicate
3
Q
Describe 2 functions of golgi apparatus:
A
- Modifies and packages proteins
- Modifies and packages lipids
4
Q
What is a proteome?
A
- All the range of proteins a cell can code for
5
Q
Describe how quaternary protein formed from its monomers
A
- Amino acids joined by peptide bond(s);
- (By) condensation reaction(s);
- Secondary structure is formed by hydrogen
bonding; - Tertiary structure formed by interactions
(between R groups); - Quaternary structure contains >1 polypeptide
6
Q
Describe structure of DNA
A
- Nucleotide= deoxyribose, phosphate and nitrogenous base
- Phosphodiester bonds between nucleotides
- Hydrogen bonding between adenine and thymine, and cytosine and guanine
- Double helix structure
- DNA is associated with histones
- DNA is a polynucleotide
7
Q
Give 2 reasons for conserving rainforests:
A
- Medicine produced
- Conserve plants/animals
8
Q
Describe how DNA is related to its function:
A
- Double-stranded allowing semi-conservative replication
- Base sequence and complementary base pairing allowing accurate replication
- Hydrogen bonds are weak so easily broken for replication
- Large so can store a lot of information
- Sugar-phosphate backbone provides strength
- Helix so compact
9
Q
Describe ways in which all dipeptides are similar in which they might differ:
A
Similarities
- Consist of 2 amino acids
- Joined by peptide bond
- Contain amine group
- Contain carboxyl group
- Contain C,H,N and O
Differences
- Contain different amino acids
- Variable R group
10
Q
Describe how a non-competitive inhibitor can reduce the rate of an
enzyme-controlled reaction
A
- Binds to the allosteric site on enzyme
- This changes the tertiary structure of the enzyme and so the active site no longer complementary
- So enzyme-substrate complexes can no longer bind
11
Q
Two proteins have the same number and type of amino acids but different
tertiary structures.
Explain why:
A
- Different sequence of amino acids
- Results in ionic,hydrogen, disulphide bonds in different places
12
Q
Describe how a phosphodiester bond is formed between two nucleotides
within a DNA molecule.
A
- Condensation reaction
- Between phosphate and deoxyribose
- Catalysed by DNA Polymerase
13
Q
Why does the DNA need to be single stranded in DNA Replication?
A
- Each strand acts as a template
- Determines the order of nucleotides
14
Q
Contrast the structures of ATP and a nucleotide found in DNA to give two
differences.
A
- ATP contains ribose whereas DNA contains deoxyribose
- ATP has 3 phosphate groups, DNA has 1
- ATP nitrogenous base is adenine whereas DNA is varied
15
Q
Why can new nucleotides can only be added in a 5’ to 3’
direction.
A
- DNA is antiparallel
- DNA Polymerase is specific
- Can only bind to 5’ end of DNA
- Shapes of 5’ and 3’ end are different
16
Q
Describe how an ATP molecule is formed from its component molecules.
A
- Condensation reaction
- Between adenine, ribose and three phosphate groups
- Catalysed by ATP Synthase
17
Q
Explain five properties that make water important for organisms.
A
- Polar so acts as a metabolite for hydrolysis and condensation reactions
- Solvent so useful in metabollic reactions
- High specific heat capacity so buffers changes in temperature
- High latent heat of vaporisation so provides a cooling effect
- Cohesive so allow movement of column of water in plants
- Cohesive so produces surface tension supporting small organisms
18
Q
Describe the roles of iron ions, sodium ions, and phosphate ions in cells.
A
- Iron= Haemoglobin transports oxygen around the body
- Sodium ions= contransport of glucose as sodium ions actively transported out of the ileum epithelial cells, lowering concentration in the cell
- Phosphate ions= joins adjacent nucleotides together, produce atp, phosphorylates other compounds, making them more reactive
19
Q
What is the cell wall of plants, fungi and bacteria made of?
A
plants= cellulose
fungi= chitin
bacteria= murein
20
Q
Why may nucleus not be visible under a microscope?
A
it is not stained
21
Q
what is the name of the membrane of a vacuole
A
tonoplast
22
Q
what is the name of membrane of chloroplast and the cytoplasm of chloroplast
A
- thylakoid membrane
- stroma
23
Q
what is the name of the membrane of the mitochondria and the cytoplasm
A
-cristae
-mitochondrial matrix
24
Q
Give one advantage of viewing a biological specimen using a transmission
electron microscope compared with using a scanning electron microscope.
A
- higher resolution so can see internal structures
25
Contrast how an optical microscope and a transmission electron
microscope work and contrast the limitations of their use when studying
cells.
- TEM uses electrons, OP uses light
- TEM has greater resolution so can see smaller organelles under microscope
- TEM can only see dead specimen, OP can view living
- TEM cant show colour, OP can
- TEM is a more complex procedure OP isnt
- TEM needs thinner specimen
- TEM focuses using magnets, OP uses glass lens
26
Name two structures in a eukaryotic cell that cannot be identified using an
optical microscope.
- Mitochondria
-Ribosomes
27
Describe how you could make a temporary mount of a piece of plant tissue
to observe the position of starch grains in the cells when using an optical
(light) microscope.
- Add a drop of water to the glass slide
- Obtain a thin slice of tissue and place flat on slide
- Stain with iodine in potassium iodide
- Gently lower coverslip with mounted needle
28
Describe binary fission in bacteria
- Circular DNA replicates
- Plasmid replicates
- Cytoplasm divides
29
What is the difference between diploid and haploid
diploid= double chromosomes so 2 complete sets of chromosomes (2n)
haploid= one set of chromosome (n)
30
How to monitor temperature in an experiment?
- take readings during the experiment using a digital thermometer
31
How does cotransport of sodium and h+ ions work?
- Using ATP
- Sodium ion and proton bind to the protein
- Protein changes shape
32
How is virus replicated?
- Attachment protein bind to specific and complementary receptor on Th cell
- Capsid released into cell and RNA released into cell
- Reverse transcriptase converts RNA into DNA
- DNA inserted in to host DNA
- Hosts organelles used to produce viral proteins
- Virus assembled and released from cell
33
Previously, the viruses infected only one species of frog. Suggest and explain how the viruses became able to infect other species
of frog.
- Mutation in the base sequence of DNA
- Altering the tertiary structure of the protein so changing shape of attachment protein so its more complementary
34
What is a monoclonal antibody?
Antibodies secreted from cloned B cells
35
What is an antigen?
- Foreign cell
- Stimulates an immune response
36
What is an antibody?
- Protein specific to antigen
- Produced by plasma cells
37
Explain how the counter-current principle allows efficient oxygen uptake in
the fish gas exchange system:
- Blood and water flow in opposite directions
- Maintains concentration gradient of oxygen along entire length of fish
- Diffusion occurs along entire length of lamellae
38
Describe and explain the mechanism that causes lungs to fill with air:
- Diaphragm contracts and external intercostal muscles contract
- Rib moves up and out
- Increases volume and decreases pressure in thoracic cavity
- So air moves down pressure gradient into the lungs
39
Suggest and explain one way the leaf growth of xerophytic plants would be
different from the leaf growth of sunflowers.
- Xerophytic have slower growth
- Lower number of stomata for gas exchange
40
Use your knowledge of gas exchange in leaves to explain why plants
grown in soil with very little water grow only slowly.
- As very little water, stomata close to conserve water
- Less carbon dioxide taken in so less respiration for growth
41
Explain three ways in which an insect’s tracheal system is adapted for
efficient gas exchange
- Tracheoles are thin so short diffusion distance
- Tracheoles are branched so increased surface area for diffusion
- Tracheoles have fluid at end which moves into tissues during exercise so faster diffusion through air to the gas exchange surface
42
Describe the processes involved in the absorption and transport of
digested lipid molecules from the ileum into lymph vessels
- Micelles contain bile salts and fatty acids
- Make monoglycerides more soluble in water
- Fatty acids and monoglycerides absorbed by diffusion
- Reform into triglycerides by smooth endoplasmic reticulum
- Vesicles move to cell membrane by exocytosis
43
Describe the role of micelles in the absorption of fats into the cells lining
the ileum.
- Micelles contain bile salts and fatty acids
- Micelles make fatty acids more soluble in water
- Fatty acids absorbed by diffusion
44
How is golgi involved in absorbing lipids
- Modifies triglycerides
- Combines triglycerides with proteins
- Packaged for release
45
Explain how water from tissue fluid is returned to the circulatory system.
- Plasma proteins remain in the blood
- Water potential decreases in the blood
- Water diffuses into the blood by osmosis
- Water returns to the blood by lymphatic system
46
How do arteries maintain blood flow?
- Elastic recoil due to muscle
- Maintain blood flow
47
Binding of one molecule of oxygen to haemoglobin makes it easier for a
second oxygen molecule to bind.
- Binding of first oxygen changes tertiary structure of haemoglobin
- Uncovers another binding site so easier to bind
48
Describe the cohesion-tension theory of water transport in the xylem.
- Water evaporates due to transpiration
- Decreased water potential in the leaf
- Water drawn up via xylem, creating tension
- Cohesive nature of water and hydrogen bonding between water molecules creates continuous column of water
- Adhesion of water to xylem walls
49
Describe the mass flow hypothesis for the mechanism of translocation in
plants
- Sucrose is actively transported into phloem sieve tube elements
- Via companion cells and ATP
- This decreases the water potential in the sieve tube elements
- Water diffuses into the phloem via the xylem by osmosis
- This increases the hydrostatic pressure in the phloem so causes mass flow of sucrose solution from source to sink
- At roots, sucrose used for respiration or stored
50
Describe how a gene is a code for the production of a polypeptide
- Base sequence
- Of triplets
- Determines the base sequence of amino acids in polypeptide
51
What is an exon
- Base sequence or triplet which codes for the base sequence of amino acids and rRNA
52
Define ‘non-coding base sequences’ and describe where the non-coding
multiple repeats are positioned in the genome.
- DNA which does not code for a polypeptide
- Found between genes
53
Suggest one way the structure of the chromosome could differ along its
length to result in the stain binding more in some areas.
- Difference in base sequences
54
What is a homologous pair of chromosomes?
2 chromosomes which carry the same genes
55
Describe differences between tRNA and mRNA
- tRNA is clover leaf shaped, mRNA is linear
- tRNA has hydrogen bonding, mRNA doesn't
- tRNA has an amino acid binding site, mRNA doesn'r
- tRNA has an anticodon, mRNA has a codon
56
Describe how a polypeptide is formed by translation of mRNA.
- mRNA attaches to ribosome
- ribosome moves to start codon
- tRNA anticodon binds to complementary codon on mRNA
- tRNA brings specific amino acid with it
- Amino acids join via condensation reaction forming peptide bond using ATP
- ribsome 'fits' around 2 codons
- tRNA released after amino acids bind
- Ribosome moves along mRNA to form polypeptide until stop codon reached
57
Give the two types of molecule from which a ribosome is made.
- rRNA
- protein
58
Describe the process of crossing over and explain how it increases genetic
diversity
- Homologous pairs of chromosomes associate forming a bivalent
- Chiasmata form
- Equal lengths of alleles are exchanged
- Forming a new combination of alleles
59
What is species richness?
- Number of different species in a community
60
What is index of diversity
- Abundance of each species
61
Why is index of diversity more useful than species richness?
- IOD measures abundance of each species
- May be more of one species
62
Give ways in which sampling procedure can be standardised
- Same sampling time
- Same time of day of samples
- Same size of area sampled
63
Give two ways the students would have ensured their index of diversity
was representative of each habitat.
- Random sampling
- Large sample size
64
What is a species
- group of organisms that can reproduce to form fertile offspring
65
What is a hierarchy?
- smaller groups within larger groups
- With no overlap
66
What are 4 things scientists can compare to determine genetic diversity
- Base sequence of amino acids
- Base sequence of DNA
- Base sequence of mRNA
- Compare features
67
suggest two reasons why populations might show very
low levels of genetic diversity.
- Population may have been very small/ genetic bottleneck
- Population may have started off small/ founder effect
68
what is meant by genetic diversity?
- number of different alleles in a gene
69
where does transcription occur in a eukaryotic cell
nucleus
70
