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biology a level > Exam Qs > Flashcards

Exam Qs Flashcards

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AP® Biology flashcards
1
Q

Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome

A

+ DNA that does not code for a sequence of amino acids/ primary structure
+ positioned between genes

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2
Q

Suggest one way the structure of the chromosomes could differ along its length

A

+ differences in base sequence

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3
Q

What is a homologous pair of chromosomes

A

+ two chromosomes that carry the same geneS

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4
Q

Describe and explain a difference in the structure of pre-mRNA and mRNA molecules

A

+ mRNA has no introns, only exons
+ because of spilicing
+ pre-mRNA more nucelotides

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5
Q

Describe how one amino acid is added to a polypeptide that is being formed at a ribosome during translation

A

+ tRNA brings specific amino acid
+ anticodon binds to codon on mRNA
+ amino acids join by condensation reaction

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6
Q

Describe how mRNA is produced from an exposed template strand of DNA

A

+ free RNA nucleotides from complementary base pairs
+ phosphodiester bonds form
+ by DNA polymerase

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7
Q

Describe how mRNA is formed by transcription in eukaryotes

A

+ hydrogen bonds break
+ one DNA strand acts as a template
+ free RNA nucleotides align by complementary base pairing
+ Uracil base pairs with adenine
+ RNA polymerase joins adjacent nucleotides
+ By phosphodiester bonds
+ pre-mRNA is spliced

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8
Q

What is the proteome?

A

+ number of different proteins that a cell is able to produce at a given time

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9
Q

Explain how pressure is generated inside the phloem tube

A

+ sucrose activity transported into phloem
+ lowering water potential
+ water moves into phloem by osmosis

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10
Q

Explain why coloured water moved up the stalks

A

+ water evaporates from leaves
+ water potential gradient causes tension
+ hydrogen bonds/ cohesion maintains column

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11
Q

Describe how digested lipids are absorbed and then transport to the ileum and lymphatic system

A

+ micelles are made of bile salts, fatty acids, monoglycerides
+ micelles carry the fatty acids to the epithelial cells of the ileum
+ fatty acids are absorbed into the cells of the ileum by simple diffusion
+ Triglycerides or chylomicrons are formed
+ vesicles are removed by exocytosis

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12
Q

Describe the importance of micelles in absorbing lipids into the epithelial cells of the ileum

A

+ micelles are made of bile salts,fatty acids, glycerol
+ micelles make fatty acids more soluble in water
+ micelles carry fatty acids to the epithelial cells of the ileum
+ the fatty acids are released from the micelle and are absorbed into the cell by simple diffusion

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13
Q

How are Golgi apparatus involved in the absorption of lipids?

A

+ they modify triglycerides
+ they combine proteins with triglycerides to form chylomicrons
+ these are packaged into vesicles

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14
Q

What is a gene

A

A sequence of DNA nucleotides that codes for a polypeptide

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15
Q

Describe how the production of mRNA in a eukaryote cell is different from the production of mRNA in a prokaryote cell

A

+ so mRNA spliced in eukaryotic because contains introns

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16
Q

Describe the role of ATP in the process of translation in protein synthesis

A

Releases energy so peptide bonds can form between amino acids

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17
Q

Describe how to process of meiosis results in haploid cells

A

+ DNA replication
+ two divisions
+ separation of homologous chromosomes
+ separation of sister chromatids
+ produces 4 cells

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18
Q

Describe how organisms are grouped in a phylogenetic classification system

A

+ hierarchy with no overlaps
+ grouped according to evolutionary relationships

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19
Q

Describe how the structure of the insect gas exchange system:
- provides cells with sufficient oxygen
- Limits water loss

A
  1. Spiracles, trachea, tracheoles
  2. Spiracles allow diffusion
  3. Tracheoles are highly branched so large surface area
  4. Tracheole walls thin so short diffusion pathway
  5. Tracheole permeable to oxygen
  6. Spiracles close so less water loss
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20
Q

Describe how the structure of a protein depends on the amino acids it contains

A
  1. Structure is determined by position of R group
  2. Primary structure is sequence of aa
  3. Secondary structure formed by hydrogen bonding
  4. Tertiary structure formed by interactions between R groups
  5. Quaternary structure contains more than one polypeptide chain
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21
Q

Differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic (evolutionary) relationships between species. Explain how.

A
  1. Mutations change base sequence
  2. Causing change in aa sequence
  3. Mutations build up over time
  4. More mutations/ differences between distantly related species
  5. Distantly related species have earlier common ancestor
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22
Q

Describe the behaviour of chromosomes during mitosis and explain how this results in the production of two genetically identical cells

A
  1. chromosomes shorten & thicken;
  2. chromosomes made from two identical chromatids, due to replication in interphase;
  3. chromosomes move to equator of the cell;
  4. Chromosomes attach to individual spindle fibres;
  5. Spindle fibres contract & the centromeres divide;
  6. Sister chromatids move to opposite poles;
  7. Each pole receives all the genetic information;
  8. Nuclear envelope re-forms around each group of chromosomes
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23
Q

Describe what happens to chromosomes in meiosis

A
  1. Chromosomes shorten & thicken;
  2. Chromosomes associate into their homologous pairs;
  3. Crossing-over occurs between chromosomes, through the formation of a chiasma;
  4. Chromosomes join to spindle fibres, via there centromeres
  5. Whilst at the equator
  6. Homologous chromosomes move to opposite poles
  7. Pairs of chromatids separated in 2nd division
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24
Q

Describe and explain how selection will have affected the genetic diversity of a species

A
  1. Diversity reduced as fewer different alleles present creating a smaller gene pool;
  2. As alleles have been chosen or rejected;
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25
Q

Describe the processes involved in the transport of sugars in plant stems

A
  1. At source sucrose is actively transported into the phloem/sieve tube;
  2. By companion cells;
  3. Lowers water potential in phloem/sieve element/tube and water enters by osmosis;
  4. This produces a high hydrostatic pressure;
  5. Mass flow/transport towards sink/roots/storage tissue occurs;
  6. At sink/roots sugars are removed/unloaded;
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26
Q

Use your knowledge of the cohesion-tension theory of water movement through a plant, to explain why the diameter of the trunk is smallest at midday

A

1.Diameter of trunk is minimal at warmest/brightest time of day;
2. Stomata are open in light → so more water loss;
3. Water evaporates more when warm as there is more heat energy for water evaporation;
4. Hydrogen-bonding between water molecules causes cohesion between water molecules;
5. Adhesion occurs between water molecules and walls of the xylem vessels;
6. The xylem is pulled inwards by faster flow of water/tension;

27
Q

Describe the difference between active and passive immunity

A
  1. Active involves memory cells, passive does not;
  2. Active involves production of antibody by plasma cells / memory cells;
  3. Passive involves antibody introduced into body from outside;
  4. Active long term, because antibody produced in response to antigen;
  5. Passive short term, because antibody given is broken down;
  6. Active can take time to develop / work, passive fast acting.
28
Q

Describe how B-lymphocytes respond when they are stimulated by antigens

A
  1. Divide by mitosis to form clones;
  2. Produce plasma cells;
  3. Plasma cells make antibodies;
  4. Plasma cells produce memory cells
29
Q

What is a monoclonal antibody?

A

Antibodies from the same plasma cell, complementary to one antigen

30
Q

Describe the induced fit model of enzyme action

A
  1. Active site of enzyme is not complementary
  2. Active site is flexible and can mould around the substrate
  3. Change in enzyme allows substrate to fit and for, an E-S complex
31
Q

Describe competitive and non-competitive inhibition of an enzyme

A
  1. Inhibitors reduce binding of enzyme to substrate & prevent the formation of E-S complexes
    (Competitive inhibition),
  2. Inhibitor has a similar shape to substrate;
  3. It binds to the active site (of enzyme);
  4. Inhibition can be overcome by adding more substrate;
    (Non-competitive inhibition),
  5. Inhibitor binds to a site on enzyme other than active site;
  6. This changes the shape of the active site
  7. Inhibition cannot be overcome by adding more substrate
32
Q

Describe the mechanism for the absorption of amino acids in the ileum

A
  1. Facilitated diffusion of amino acids
  2. Co transport
  3. Sodium ions actively transported from cell to blood
  4. Creating sodium ions concentration gradient
  5. Facilitated diffusion of amino acids into blood
33
Q

Give the two types of molecule from which a ribosome is made

A
  1. rRNA
  2. Protein
34
Q

Describe and explain one difference between SEM and TEM

A
  1. SEM is 3D, TEM is 2D
  2. In SEM electrons are deflected
35
Q

Name two structures found in all bacteria that are not found in plant cells

A
  1. Circular DNA
  2. MUREIN cell wall
36
Q

Name two features of HIV particles that are not found in bacteria

A
  1. Reverse transcriptase
  2. Capsid
37
Q

Explain a property of iron ions that enables these ions to carry out their role in red blood cells

A
  1. Polar
  2. So binds/associates with oxygen
38
Q

What is a tumour

A
  1. Mass of cells
  2. Caused by uncontrolled mitosis/cell division
39
Q

Describe how you would determine a reliable MI from tissue observed with an optical microscope

A
  1. Count cells in mitosis in FOV
  2. Divide this by total number of cells in FOV
  3. Select FOV at random or repeat many times
40
Q

Suggest why the number of bacteria would be lower if the student didn’t use a sterilised pipette

A
  1. Unknown/ new bacteria/ pathogen introduced
  2. These bacteria use food/ space/ produce toxins
41
Q

Why are antibiotics ineffective against viruses

A
  1. Viruses lack cell structures for antibiotics to work on
  2. Antibiotics cannot reach viruses as they are found within host cells
42
Q

Explain how cellulose is adapted for its function in plant cells

A
  1. Long and straight/ unbranched chains
  2. Chains linked together via hydrogen bonds
  3. Form microfibrils
  4. Provide strength (to cell wall)
43
Q

Describe one structural difference between glycogen and starch

A

Glycogen is more highly branched than starch

44
Q

Explain how glycogen’s structure enables it to function as an energy storage molecule

A
  1. Coiled so compact
  2. Branched so more ends for faster hydrolysis
  3. Insoluble so it does not affect water potential
  4. Made up of glucose can be used in respiration
45
Q

Not all mutations in the nucleotide sequence of a gene causes a change in the structure of a polypeptide. Explain why.

A

1.Triplet code is degenerate
2. Occurs in introns

46
Q

Give one example of using monoclonal antibodies in a medical treatment

A
  1. Binds to specific antigens or cancer cells
47
Q

Describe the role of antibodies in producing a positive results in an ELISA test

A
  1. First antibody binds to complementary antigen
  2. Second antibody with enzyme attached is added
  3. Second antibody attaches to antigen
  4. Substrate added and colour changes
48
Q

Why does a colorimeter improve the repeatability of results

A
  1. Quantitative value
  2. Standardises the method
49
Q

Suggest how to measure the water flow

A

Use a data logging device

50
Q

Describe the three properties of the solution used for centrifuging

A
  1. Cold to reduce damage by enzymes activity
  2. Buffered to prevent denaturing of enzyme
  3. Same water potential to prevent bursting of organelle
51
Q

Explain how the active site of an enzyme causes a high rate of reaction

A
  1. Lowers activation energy
  2. Induced fit causes active site to change shape
  3. Enzyme-substrate complex causes bonds to form
52
Q

Describe two ways in which all dipeptides are similar and one way in which they might differ

A
  1. Both contains amine group
  2. Both contain carboxyl group
  3. Different R groups
53
Q

State and explain the property of water that can help to buffer changes in temperature

A
  1. High specific heat capacity
  2. Takes a lot of energy to change temperature
54
Q

Describe the pathway taken by an oxygen molecule from an alveolus to the blood

A
  1. Alveolar epithelium
  2. Endothelium of capillary
55
Q

Explain why the biologist had to dilute the blood sample

A

Make it easier to count

56
Q

Explain what features would make a pair of chromosomes homologous

A
  1. Carry same genes in the loci of genes
  2. Similar length
  3. Centromere in same position
57
Q

What effect does increasing concentration of substrate have on non competitive inhibitors

A

No effect

58
Q

Explain how a reduction in lung elasticity can make it feel harder to breathe

A
  1. Lungs will not inflate
  2. Breathing out no longer passive
59
Q

Explain how scar tissue on alveoli walls reduces the efficient of gas exchange

A

Reduces surface area for gas exchange

60
Q

Give two reasons why biodiversity should be maintained

A
  1. Ethical duty to prevent extinction
  2. Potential source of medicines
61
Q

Explain how water and ions are transported in the vascular tissue from roots to the leaves

A
  1. Water evaporates at the leaves
  2. Lowers water potential gradient
  3. Cohesion between water molecules
62
Q

Describe two ways the genetic diversity within a crop species could be analysed

A
  1. Comparing base sequence of DNA
  2. Comparing base sequence of RNA
63
Q

Explain why viruses are not classified with the other living organisms

A
  1. Acellular
  2. Cannot reproduce without a host organism

biology a level (21 decks)

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