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AS AQA BIOLOGY > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

What is a cell?

A

the smallest structural and functional unit of an organism, which is typically microscopic and consists of cytoplasm and a nucleus enclosed in a membrane.

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2
Q

How does wavelength affect the resolution of a microscope?

A

Light has a longer wavelength so objects are harder to distinguish between lowering the resolution

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3
Q

how do you calculate magnification?

A

size of image / size of real object

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4
Q

How do you calculate real object size?

A

size of image/magnification

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5
Q

How do you calculate the image size?

A

magnification x size of real object

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6
Q

how do you convert mm into um?

A

X1000

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7
Q

how do you convert mm into nm?

A

X100,000

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8
Q

how do you convert nm into mm?

A

/100,000

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9
Q

how do you convert um into mm?

A

/1000

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10
Q

What does resolution mean?

A

The minimum distance apart that two objects can be in order for them to appear as separate items

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11
Q

What does magnification mean?

A

How many times larger the image is compared to the object

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12
Q

What is the max. resolution of a light microscope?

A

0.2 um

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13
Q

What is the max. resolution of an electron microscope?

A

0.1 nm

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14
Q

Greater resolution means…

A

greater clarity; the image produced is more clear and precise

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15
Q

What is cell fractionation?

A

A process where cells are broken up and the different organelles they contain are separated out

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16
Q

Describe the solution cells are placed in before cell fractionation.

A

Cold, buffered, isotonic

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17
Q

Why must the solution a cell is fractionised in be cold?

A

to reduce enzyme activity that might breakdown organelles

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18
Q

Why must the solution a cell is fractionised in be isotonic?

A

to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water

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19
Q

Why must the solution a cell is fractionised in be buffered?

A

so the pH remains constant to prevent altering organelle structure or enzyme function

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20
Q

What are the two stages of cell fractionation?

A

Homogenation and Ultracentrifugation

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21
Q

What is homogenation?

A

When cells are broken up by a homogeniser

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22
Q

What is the purpose of homogenation?

A

To release the organelles from their cells

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23
Q

What is homogenate?

A

The fluid left over from cell homogenisation

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24
Q

Why must the homogenate be filtered?

A

To remove unhomogenised cells and large pieces of debris

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25
Q

What is ultracentrifugation?

A

A process where cell fragments in a filtered homogenate are separated in a centrifuge

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26
Q

What is a centrifuge?

A

A machine that spins tubes of homogenate at very high speed in order to create a centrifugal force

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27
Q

Describe the ultracentrifugation process.

A
  1. Homogenate is decanted into a tube and spun at a low speed
  2. Heavier organelles are forced to the bottom of the tube forming a pellet or thin sediment
  3. The supernatant is removed leaving the pellet or thin sediment
  4. The supernatant is transferred to another tube and centrifuged again at a higher speed
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28
Q

What is the supernatant?

A

The remaining fluid at the top of the tube after centrifugation

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29
Q

What are the heavier cell organelles?

A

Nucleus, mitrochonria

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30
Q

What are the lighter cell organelles?

A

Ribosomes, lysosomes

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31
Q

How does an electron microscope have a higher resolution?

A

The electron beam has a shorter wavelength

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32
Q

How can an electron microscope be focused?

A

Using electromagnets, as electrons are negatively charged

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33
Q

Why must the object be placed in a vacuum when viewed under an electron microscope?

A

Electrons are absorbed or deflected by particles in the air preventing the object from being seen clearly

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34
Q

What are the two types of electron microscope?

A

Transmission (TEM) and Scanning (SEM)

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35
Q

What are pros of light microscopes?

A

Coloured dyes can be added to provide coloured/contrasted images
Livingcells can be viewed
No artefacts are produced

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36
Q

What are the cons of light microscopes?

A 
Low resultion due to lights short wavelength
Low magnification (x1500)
Specimen needs to be thin
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37
Q

What are the pros of SEMs?

A

Higher resolution and magnification than a light microscope
Specimen sections don’t need to be thin
Gives a 3D surface image of the cell

38
Q

What are the cons of SEMs?

A

Image is not coloured
Living cells cannot be viewed
Artefacts may appear due to complicated preparation
Magnification and Resolution are lower than TEM

39
Q

What are the pros of TEMs?

A

Highest resoltion and magnification (x1,500,000)

Shows internal cell structure

40
Q

What are the cons of TEMs?

A

Image is not coloured
Living cells cannot be viewed
Artefacts may appear due to complicated preparation
Specimen must be very thin

41
Q

What is an artefact?

A

A structure or substance not normally present but produced by an external agent or action, such as a structure seen in a microscopic specimen after fixation that is not present in the living tissue

42
Q

Name 3 cell features/organelles present in all eukaryotic cells

A

Nucleus, mitrochondria, smooth/rough er, ribosomes, golgi aparatus, lysosomes, cell suface membrane, cytoplasm

43
Q

Name 3 cell features/organelles only present in plant cells

A

Vacuole, chloroplasts, cell wall

44
Q

Name 3 cell features/organelles present in Eukaryotes but not Prokaryotes

A

Nucleus, mitrochondria, golgi apparatus, lysosome, Smooth/Rough ER

45
Q

Name 3 cell features/organelles present in Proaryotes but not Eukaryotes

A

Capsule, Plasmids, Circular DNA, Flagella

46
Q

Name 3 cell features/organelles present in all prokaryotic cells

A

Cytoplasm, cell-surface membrane, cell wall, capsule, plasmids, circular DNA, flagellum, ribosomes

47
Q

What is the function of the nucleus?

A

Controls the activities of the cell and makes DNA, mRNA, tRNA and rRNA

48
Q

What is the function of mitrochondria?

A

Location of aerobic respiration (Kreb’s cycle and electron transport chain) to produce nATP and other metabollic intermidiates (eg. amino acids)

49
Q

What is the function of the cell-surface membrane?

A

Provides structure to the cell and regulates substance movement into and out of the cell.

Also allows communication and recognition

50
Q

What is the function of a chloroplast?

A

Site of photosynthesis, only present in plant cells

51
Q

What is the function of the golgi apparatus?

A

Modifies and packages new proteins and lipids, produces golgi vesicles and lysosomes

52
Q

What is the function of the golgi vesicle?

A

Stores lipids and proteins and transports them out of the cell

53
Q

What is the function of lysosomes?

A

Contains digestive enzymes (lysozymes) for destroying worn-out organelles and engulfed products of endocytosis, digesting invading cells

54
Q

What is the function of ribosomes?

A

Site of proteinsynthesis, translates mRNA into proteins

55
Q

What is the function of the rough endoplasmic reticulum?

A

Folds and processes proteins produced by ribosomes

56
Q

What is the function of the smooth endoplasmic reticulum?

A

Synthesises and processes lipids

57
Q

What is the function of the cell wall?

A

Supports the cell and prevents the cell changing shape

58
Q

What is the function of the cell vacuole?

A

Maintains pressure inside the cell and keeps the cell ridged to prevent the plant from wilting

Isolates unwanted chemicals in the cell

59
Q

What is the function of the capsule?

A

Protects bacterium from attack by immune system cells

60
Q

What is the function of plasmids?

A

Contain genes that can be passed between prokaryotes

61
Q

What is the function of flagella?

A

Allows the cell to move

62
Q

What is the function of attachment proteins?

A

Allows the virus to identify and attach to a host cell

63
Q

What is the function of the capsid?

A

Contains the nucleic acids of the virus

64
Q

What are the features of the nucleus?

A

Nucleolus, nuclear envelope, nuclear pores, nucleoplasm, chromatin

65
Q

What are the features of the mitrochondria?

A

double membrane, cristae, matrix

66
Q

What are the features of the cell surface membrane?

A

Bilayer of phospholipids, cholesterol, proteins, glycoproteins, glycolipids

67
Q

What are the features of endoplasmic reticulum?

A

cisternae, lamellae, ribosomes (RER)

68
Q

What are the features of chloroplasts?

A

stroma, grana, lamella, chloroplast envelope, thykaloid

69
Q

What are the features of golgi apparatus?

A

cisternae, vesicles, lumen, transface, cisface

70
Q

What is the function of the nucleolus?

A

manufactures RNA and ribosomes

71
Q

What is the function of the nuclear envelope?

A

controls entry-exit of the nucleous

72
Q

What is the function of the nuclear pores?

A

allows large molecule passage

73
Q

What is the function of chromatin

A

consists of protein bound linear DNA

74
Q

What is the function of the double membrane?

A

controls entry and exit of material

75
Q

What is the function of cristae?

A

extensions of the inner membrane providing a large surface area for enzyme and protein

76
Q

What is the function of the matrix?

A

contains lipids, proteins, ribosomes and DNA, allowing protein production

77
Q

What is the function of the cisternae

A

Contains enzymes to prevent any redundant enzymatic activity

78
Q

What is the function of the chloroplast envelope?

A

selects what enters and exists the chloroplast

79
Q

What is the function of the grana (thylakoids)?

A

Contains chlorophyll for photosynthesis and light absoption

80
Q

What is the function of the stroma?

A

a fluid filled matrix where the sugars are synthesised for photosynthesis

81
Q

What are the differences between prokaryotes and eukaryotes?

A

PROKARYOTES - Baterium, 0.1-10 um (typically 1um) 70s ribosomes, cell wall made of murein or peptidoglycan, binary fission

EUKARYOTES - Animal plant or fungi, 10-100 um, 80s ribosomes, cell wall made of celluloseor chitin, mitosis and meiosis

82
Q

What are the steps of binary fission?

A
  1. Circular DNA and plasmids replicate
  2. Cell enlarges and dna loops move to poles
  3. Cytoplasm divides producing two daughter cells
83
Q

What are the steps of viral replication?

A
  1. Virus attaches to host cell via receptor proteins
  2. Genetic material is released into cell
  3. Genetic material replicated by host cell
  4. Viral components assemble
  5. Replicated viruses leave from host cell
84
Q

What are the four stages of the cell cycle?

A

Mitosis, Gap Phase 1, synthesis/interphase, gap phase 2

85
Q

Describe the steps of interphase

A
  1. DNA unravels and is replicated
  2. Organelles are replicated
  3. ATP content is increased
  4. Protein production increases
86
Q

Describe the steps of prophase

A
  1. Chromosomes condence into sister chromatids
  2. Centrioles move to poles forming spindle fibres
  3. Nuclear envelope breaks down and nucleolus disappears
87
Q

Describe the steps of metaphase

A
  1. Sister chromatids line up in centre of cell

2. Joined to spindle apparatus by centromere

88
Q

Describe the steps of anaphase

A
  1. The centromeres divide separating the sister chromatids into chromosomes
  2. The spindle fibres contact pulling the chromatids to the poles
89
Q

Describe the steps of telophase

A
  1. The chromatids uncoil and become long and thin
  2. The nuclear envelope forms again
  3. The cytoplasm begins to divide
90
Q

Describe the steps of cytokinesis

A
  1. The cytoplasm divides

2. Two daughter cells are produced

AS AQA BIOLOGY (8 decks)

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