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Biology Edexcel B A Level > Topic 2 Cells, Viruses And Reproduction (X 2.2) > Flashcards

Topic 2 Cells, Viruses And Reproduction (X 2.2) Flashcards

1
Q

What are the two categories of cells?

A

Prokaryotic cells
Eukaryotic cells

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2
Q

8Common features of prokaryote cells

A
  1. Cell wall
  2. Capsule
  3. Cell membrane
  4. Mesosome
  5. Nucleoid
  6. Plasmids.
  7. Ribosomes
  8. Flagella and pili
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3
Q

What are cell walls of bacteria made of?

A

Peptidoglycan

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4
Q

What is the function of cell walls?

A

Prevents cell bursting and give bacteria its shape

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5
Q

What are capsules made up of?

A

Various molecules
Eg starch or glycolipids

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6
Q

Where are capsule found?

A

Only on some bacteria

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7
Q

What are the functions of capsule?

A

Protects bacterium from drying out in certain conditions
Protects being discovered in the immune system
Can enhance the ability of bacteria to cause disease

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8
Q

What is the function of cell membranes?

A

Control substances entering and exiting the cell

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9
Q

What are mesosomes?

A

They are artefacts

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10
Q

What is a nucleoid?

A

DNA in prokaryotic cells in the form of one long sing strand aka nucleoid

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11
Q

Where is the nucleoid found in prokaryotic cells?

A

Free in the cytoplasm, not in a membrane

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12
Q

What are plasmids?

A

Small circular loops of DNA

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13
Q

What do plasmids do?

A

Circular DNA carried by bacteria
Can be transferred between bacteria, eg confer resistance to antibiotics

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14
Q

What do ribosomes do?

A

Protein synthesis

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15
Q

Compare ribosomes in prokaryotic and eukaryotic cells

A

Ribosomes in prokaryotic cells are smaller (70s)
Made up of 30S + 50S

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16
Q

What does flagella do?

A

Movement for bacteria

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17
Q

What are flagella and pili made up of?

A

Protein fibres called flagellum which are spun around like a motor

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18
Q

What are pilus used for?

A

To help bacteria reproduce and communicate and attach to surfaces

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19
Q

How can contents of cell be separated to determine size and mass?

A

Use a centrifuge
(Spinning at high speed, centripetal force separates cells of diff mass)

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20
Q

What is the cell theory?

A

That everything is made up of cells

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21
Q

How are organisms organised?

A

Cells Into tissues into organs into organ systems

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22
Q

Define ultra structure

A

The details of inside of cell

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23
Q

Define organelle

A

Each structure within a cell

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24
Q

What is the structure of a nucleus?

A

Surrounded by a double membrane called nuclear envelope
Contains chromatins and nuclear pores

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25
Q

Function of nucleolus

A

Produces ribosomes and RNA

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26
Q

What are ribosomes made up of?

A

Ribosomal RNA and protein

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27
Q

What is the function of ribosomes?

A

Used during protein synthesis and assemble polypeptide

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28
Q

Describe the structure of Rough endoplasmic reticulum

A

Made from flattened sacs of membranes called cisternae
Has ribosomes dotted along the surface

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29
Q

What is the function of rough endoplasmic reticulum?

A

Folds and processes proteins made on the ribosomes

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30
Q

What is the smooth endoplasmic reticulum made up of?

A

Just cisternae

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31
Q

What is the function of smooth endoplasmic reticulum?

A

Manufacture lipids, phospholipid and steroids (hormones)

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32
Q

What is the structure of mitochondria?

A

Capsule shape filled with MATRIX
Has its own circular DNA in the matrix

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33
Q

What is the function of mitochondria?

A

Provide large SA for aerobic cellular respiration for ATP production

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34
Q

How permeable are cell walls?

A

Freely permeable

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35
Q

What membrane are chloroplasts?

A

Double membrane

36
Q

What do chloroplasts contain?

A

Thylakoids
Granum (stack of thylakoids )
Chlorophyll
Stroma

37
Q

What DNA is found in chloroplasts?

A

Circular dna

38
Q

What is a vacuole in prokaryotes filled with?

39
Q

What are the functions of vacuoles in prokaryotes?

A

Storage
Maintain cell shape

40
Q

What is a tonoplast?

A

Membrane that surrounds the vacuole

41
Q

What’s the function of tonoplasts?

A

Control osmotic potential of cells

42
Q

How are centrioles found?

A

In A pair near the nucleus at right angles
Bundle of 9 microtubule triplets
Only in animal cells

43
Q

What is the function of centrioles?

A

Used when cell divides,
Hold organelles together

44
Q

What is cytoskeleton?

A

Fibrous network that fills the cytoplasm

45
Q

What is cytoskeleton made up of?

A

Microtubules and microfilaments

46
Q

What is the function of cytoskeleton?

A

Present in cytoplasm
Holds organelles together
Allow movement of organelles
Gives cells structure

47
Q

How are lysosomes found?

A

In cytoplasm
Dark spherical organelles

48
Q

Where are lysosomes produced?

49
Q

What do lysosomes do?

A

Catalyse reactions eg breaking down old organelles (digestive enzyme)
Exocytosis (by fusing with cell membrane and release out of cell)

50
Q

What is Golgi apparatus made up of?

A

Stacks of cisternae
And
Vesicles

51
Q

What do Golgi apparatus look like?

A

Coral like

52
Q

Describe the role of Golgi apparatus in secreting enzymes. (3 marks)

A
  • vesicles containing protein/enzyme from rER packaged and fuse with Golgi
  • proteins modified
  • proteins leave in vesicles
  • by exocytosis / vesicles fuse with cell membrane
53
Q

What are stages in mitosis?

A

PMAT
prophase- dna condenses to chromosomes, nuclear envelope break down
Metaphase-centrioles form spindle fibres, align in equator
Anaphase- spindle fibres contract, centromeres divide to each pole, sister chromatids become individual chromosomes
- telophase- decondense of chromosomes, spindle fibres break down, nuclear envelope reform

54
Q

What are stages of meiosis I and II?

A

P1- crossing over, nuclear envelope break down, centrioles move to opposite poles
M1- independent assortment of homologous pairs
A1- separate homo. Pairs pulled to poles, ATP used
T1- X
P2-2nd cell division
M2- random assortment of
A2- centromeres divide, random separation
T2- nuclear envelope reform
Cytokineses - 4 haploid cells formed

55
Q

Compare mitosis and meiosis

A

Somatic cells vs gamete cells
1 vs 2 cell divisions
46 vs 23 chromosomes
2 identical diploid vs 4 different haploid cells
Growth rep are and reproduce, vs only sexual reproduction

56
Q

What’s translocation in chromosomes?

A

When 2 non homologous parts of genes transferred not another, forming unbalanced length of chromosome

57
Q

What is non disjunction?

A

When chromosomes didn’t seperate correctly at anaphase - one will have too many and one too few chromosomes

58
Q

What are the oogenesis products called? And their number of chromosomes?

A

Primordial germ cell > mitosis> Oogonia (2n) > primary oocyte (2n) > secondary oocyte (n) + first polar body (at puberty)> ovum (n) + second polar body

59
Q

What are the spermatogenesis products called? And their number of chromosomes?

A

Primordial germ cell (2n) > spermatogonia (2n) > primary spermatocyte (2n) > secondary spermatocyte (n) > spermatids > spermatozoa (tails)

60
Q

What are the two nuclei that lands on sigma and digests its way down the style to the ovule?

A

Pollen tube nucleus
Generative nucleus

61
Q

What are the stages and products of megametogenesis?

A

Megastore mother cells divide by meiosis, 4 haploid MEGASPORES produced, 1 grows (3 degenerates) and mitosis 3 times
Forms 7 cells (1 has 2 haploid polar nuclei)

62
Q

What stain is used to identify stages of mitosis?

A

Toludine blue

63
Q

Devise a method for student to investigate effect of waterlogged soil on mitosis in root cells (4 marks)

A
  • same type of plant
  • same length of root tip
  • find mitosis index
  • leave for the same period of time
64
Q

Why must appropriate stain be used to see stages of mitosis? (2 marks)

A

Dye attaches to cells in order for chromosomes to be visible

65
Q

Why is a juvenile aphid genetically identical to its parent?

A

Asexual reproduction via mitosis
DNA replication takes place,
Dividing sister chromatids equally

66
Q

What chromosome mutation is Down’s syndrome?

A

Non disjunction

67
Q

What is the role of enzyme ligase in DNA replication?

A

Attach Okazaki fragments together
Via phosphodiester bonds between each nucleotide

68
Q

Which type of cell division produces female gametes in female bees?given fertilised eggs develop into diploid females, unfertilised eggs develop into haploid males.

A

Meiosis since they need to be fertilised
So forms haploid gametes

69
Q

What holds 2 chromatids together?

A

CentroMEREs

70
Q

Explain the significance of meiosis in living organisms (3 marks)

A

Allows genetic variation
So natural selection can take place for advantageous alleles
Better.chance of survival under evolving selection pressures

71
Q

What are 2 advantages of mitosis?

A

Rapid reproduction
Doesn’t need another mate/plant

72
Q

Describe the process of crossing over during meiosis (3 marks)

A
  • 2 homologous chromosomes line up
  • chiasmata forms, exchanging genetic info
  • break in DNA
73
Q

Why do cells carry out mitosis? 2 marks

A

Growth, repair and replace of cells
Produce genetically identical cells

74
Q

How does translocation occur?

A

When a part of a chromosome breaks off and joins to a non homologous chromosome

75
Q

What does the term allele mean?

A

Different form of a gene

76
Q

What stains are used to identify gram positive or negative cell walls?

A
  1. Crystal violet (attached to G+ only, becomes violet)
  2. Rinse w water, add iodine solution
  3. Red safranin (G- becomes pink)
77
Q

Gram negative is more resistant bcs…

A

it has an outer phospholipid layer protecting the cell wall unlike the gram positive. The antibiotic is blocked from the cell wall by this phospholipid bilayer making it much more difficult to treat.

78
Q

Describe the role of the Golgi apparatus in producing secreted enzymes. (3 marks)

A
  • vesicles containing enzyme protein from rER fuse with Golgi
  • proteins modified
  • proteins leave Golgi in vesicles
  • vesicles fuse with cell membrane by exocytosis
79
Q

Why do eukaryotic cells need mitochondria but prokaryotic cells don’t? (2 marks)

A
  • mitochondria compacts enzymes and substrates tgt in one place
  • so enzyme reactions are faster
  • bacteria can use their cell membranes to respire
80
Q

Describe the effects of ethanol on plant cell membranes. (2 marks)

A
  • damages phospholipid
  • so cell membrane becomes more permeable
81
Q

Explain the structure of the membrane controls the transport of polar molecules. (4 marks)

A

Head is hydrophilic - on the outside
Tail is hydrophobic on the inside
Polar / charged substances can’t pass through hydrophobic tails
Passes through carrier proteins instead

82
Q

Describe how insulin is modified, packaged and secreted by a cell. (4 marks)

A
  • rER insulin is folded
  • insulin packaged into vesicles
  • vesicles fuse with Golgi
  • insulin structure modified by Golgi
  • vesicles fuse with cell membrane and exocytosis to secret
83
Q

What is the type of division that undifferentiated plant cells meristems undergo?

85
Q

Give 2 differences between the structures of a prokaryotic and eukaryotic cell. (2 marks)

A

Pro / Eu
No nucleus / yes
Smaller ribosomes, 70S / larger, 80S
Cell wall contains Peptidoglycan / does not

Biology Edexcel B A Level (22 decks)

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