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OCR Biology AS H020 > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

What is a eukaryotic cell?

A

Cells with a nucleus and other membrane bound organelles, they make up multicellular organisms.

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2
Q

Define metabolism…

A

The synthesis and breaking down of molecules.

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3
Q

What is the purpose of compartmentalisation?

A

To provide distinct environments and conditions for cellular reactions.

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4
Q

What is a prokaryote?

A

Single celled organisms with a single undivided cytoplasm.

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5
Q

What is cytoplasm composed of?

A

Cytosol (water, salts and organic molecules)

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6
Q

What is an organelle?

A

Membrane-bound compartment.

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7
Q

Describe the membrane surrounding an organelle?

A

Membranes are selectively permeable and control the movement of substances into and out of the cell.

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8
Q

Describe the components of the nucleus…

A

DNA is contained within a double membrane called the nuclear envelope, this protects it from damage in the cytoplasm.
The double membrane contains nuclear pores to allow movement in and out (RNA).
Nucleolus.

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9
Q

Describe how DNA forms chromosomes…

A

DNA associates with histones (proteins) to form chromatin which coils and condenses to form chromosomes.

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10
Q

What is the nucleolus?

A

An area within the nucleus responsible for producing ribosomes (rRNA), it is composed of RNA and proteins.

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11
Q

What is the function of mitochondria?

A

It is the site of the final stages of cellular respiration where ATP (adeninetriphosphate) is produced.

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12
Q

Describe the membrane structure of mitochondria…

A

Mitochondria has a double membrane structure, The inner membrane is highly folded to form cristae which contain the enzymes.

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13
Q

What is the fluid interior of mitochondria called?

A

The matrix.

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14
Q

What are cristae?

A

The highly folded inner membrane of mitochondria, it contains the enzymes for cellular respiration.

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15
Q

What is mt(DNA)?

A

Mitochondrial DNA found in mitochondria which means they can produce their own enzymes and reproduce themselves.

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16
Q

What are vesicles?

A

Membranous sacs with storage and transport roles inside the cell. They have a single membrane and an interior fluid.

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17
Q

What are lysosomes?

A

Specialised vesicles that contain hydrolytic enzymes responsible for breaking down waste material in the cells.

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18
Q

Give 3 examples of the uses of hydrolytic enzymes in lysosomes…

A 
Breaking down old organelles.
Immune system (pathogens ingested by phagocytic cells).
Apoptosis.
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19
Q

Name the 3 components of the cytoskeleton…

A

Microfilaments, microtubules and intermediate fibres.

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20
Q

What is the general function of the cytoskeleton?

A

It is a network of fibres responsible for cell shape and stability. It controls cell movements and movement of organelles within cells.

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21
Q

What are microfilaments?

A

Contractile fibres made from actin, responsible for cell movement/contraction during cytokinesis.

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22
Q

What part of the cytoskeleton is made from actin?

A

Microfilaments.

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23
Q

What are microtubules and how are they formed?

A

They act as tracks for vesicles and form spindle fibres. They form when globular tubulin polymerises to form tubes.

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24
Q

What is the function of intermediate fibres?

A

To give the cell mechanical strength and maintain cell integrity.

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25
Q

Describe centrioles…

A

Centrioles are a component of the cytoskeleton, they are composed of microtubules. 2 associated centrioles form thr centrosome which is involved in the assembly snd organisation of spindle fibres.

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26
Q

Centrioles are not present in _____ ?

A

Flowering plants or fungi.

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27
Q

In simple terms, what are flagella and cilia?

A

Protruding extensions from cells.

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28
Q

What is the function of flagella?

A

To enable motility, it is also a sensory organelle.

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29
Q

How do cilia move objects?

A

They beat rhythmically creating a current causing adjacent objects to move

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30
Q

Give two examples of where cilia is present in the human body…

A

Trachea and fallopian tubes.

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31
Q

Explain the ‘9+2’ arrangement of mobile cilia…

A

Each cilium contains 2 central microtubules surround by 9 pairs of microtubules. Parallel pairs slide over each other causing the cilia to beat.

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32
Q

What is the function of smooth ER (endoplasmic reticulum)?

A

Lipid and carbohydrate synthesis and storage.

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33
Q

What is secretion?

A

Transport out of a cell.

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34
Q

What is the function of rough ER (endoplasmic reticulum)?

A

Protein synthesis and transport.

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35
Q

What is the difference between smooth ER and rough ER?

A

Rough ER has ribsomes bound to it’s surface.

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36
Q

What is ER?

A

Endoplasmic reticulum, a network of membranes enclosing flattened sacs called cisternae.

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37
Q

What are cisternae?

A

Flattened sacs enclosed in ER and golgi apparatus.

38
Q

Secretary cells have more/less ER?

A

More.

39
Q

Describe ribsomes…

A

Ribosomes have no membrane, are made of rRNA and are the site of protein synthesis.

40
Q

`Where are ribsomes found?

A

Free floating in the cytoplasm, attached to rough ER, mitochondria, chloroplasts and prokaryotic cells.

41
Q

What is the function of the golgi apparatus?

A

It modifies and packages proteins into vesicles, it is formed of cisternae.

42
Q

Where do proteins fuse at the golgi apparatus?

A

Cis face.

43
Q

Where do proteins leave the golgi apparatus?

A

Trans face.

44
Q

State the order of organelles involved in protein synthesis and transport.

A

Ribosomes (rough ER), golgi apparatus, vesicles, cell surface membrane.

45
Q

Which organelles are specific to plant cells?

A

Cell wall, vacuoles, chloroplasts.

46
Q

What is a plant cell all composed of?

A

Cellulose.

47
Q

Describe the plant cell wall…

A

It provides shape as the cell contents press against it making it rigid, it acts as a defence mechanism from invading pathogens.

48
Q

What type of permeability is the cellulose cell wall?

A

Freely permeable.

49
Q

What are vacuoles?

A

Membrane lined sacs in the cytoplasm containing cell sap, they maintain turgor.

50
Q

What us the vacuole membrane called, and what type of permeability is it?

A

Tonoplast - selectively permeable.

51
Q

What is the function of chloroplasts?

A

Responsible for photosynthesis.

52
Q

What type of membrane do chloroplasts have?

A

Double membrane.

53
Q

What is the fluid interior of a chloroplast called?

A

Stroma.

54
Q

What are thylakoids?

A

An internal network of membranes which form flattened sacs in chloroplasts.

55
Q

Several thylakoids stacked together are called ____?

A

A granum (pl. grana).

56
Q

What do the grana contain in chloroplasts?

A

Chlorophyll pigments and starch produced during photosynthesis present as starch grains.

57
Q

How are grana connected in chloroplasts?

A

Lamellae.

58
Q

State cell theory…

A

Both plant and animal tissue is composed of cells, cells are the basic unit of all life, cells only develop from existing cells.

59
Q

How many lenses does a compound light microscope have?

A

2, the objective lens (near specimen) and ocular lens. Illumination is provided by a light under the species.

60
Q

What are the 4 types of slides that can be prepared?

A

Dry mount, wet mount, squash slide and smear slide.

61
Q

How do you prepare a dry mount?

A

Solid specimens are sectioned and placed on a slide with a cover slip, lowered using a mounting needle.

62
Q

What is a wet mount?

A

Species suspended in a liquid.

63
Q

How do you prepare a squash slide?

A

A wet mount is prepared, a lens tissue is used to press down the cover slip.

64
Q

How do you prepare a smear slide?

A

Th edge of a slide is used to smear the sample.

65
Q

Why is it important to stain slides?

A

To increase the contrast between different components within a cell as they take up stains to different degrees.

66
Q

What is differential staining?

A

Distinguishes between different types of organisms.

67
Q

What is the process of preparing a permanent slide?

A

Fixing, sectioning, staining and mounting.

68
Q

What is fixing?

A

Preservation with chemicals.

69
Q

What is sectioning?

A

Dehydrating and slicing.

70
Q

What is mounting?

A

Securing a specimen to a slide.

71
Q

Define magnification…

A

How many times larger the image is than the actual size of the object being viewed.

72
Q

Define resolution…

A

The ability to see individual objects as separate entities.

73
Q

How do you calculate magnification?

A

Magnification = Size of Image/Actual Size of Object

74
Q

Describe the process of magnification calibration…

A

Line up the stage micrometer with the eyepiece graticule and focus the microscope. Count the number of divisions and um between 2 points of coincidence.

75
Q

Why do electron microscopes have a higher resolution than compound light microscopes?

A

Their wavelength is smaller hence individual beams can be much closer before they overlap (diffraction).

76
Q

What is the calibration calculation?

A

Each eyepiece division = Number of EPD’s/micrometers

77
Q

What is an electron microscope?

A

A beam of electrons with a wavelength of less that 1nm is used to illuminate a specimen.

78
Q

Give 3 disadvantages of electron microscopes…

A

Expensive, controlled environments, artefacts.

79
Q

What is a transmission electron microscope?

A

Electrons are transmitted through a species and focused to produce an image.

80
Q

What is the resolving power of an electron transmission microscope?

A

0.5nm

81
Q

What is a scanning electron microscope?

A

An electron beam is sent across the surface of a specimen and reflected electrons are collected. It can produce 3D images.

82
Q

What is the resolving power of an electron scanning microscope?

A

3-10nm

83
Q

What are artefacts?

A

Visible structural details caused by processing the specimen.

84
Q

What is a laser scanning confocal microscope?

A

Moves a single spot of focused light across a specimen causing fluorescence from components labelled with a dye. Emitted light from the specimen is filtered through a pinhole. 3D images can be created if multiple images are taken.

85
Q

Which microscopes can produce 3D images?

A

Laser scanning confocal and scanning electron microscopes.

86
Q

Describe the DNA in prokaryotes…

A

There is no nucleus, so DNA is free floating in the cytoplasm as a nucleoid/plasmids (1 molecule). 1 supercoiled chromosome (compact). Genes grouped into operons hence a number are switched on or off at any one time. DNA is circular not linear.

87
Q

What are operons?

A

Groups of genes in prokaryotes.

88
Q

Describe ribosomes in prokaryotes…

A

They are smaller 70S compared to 80S.

89
Q

What does 70S/80S mean?

A

The rate at which ribosomes settle/form sediment in solution.

90
Q

What is the cell wall made from in a prokaryote?

A

Peptidoglycan (murein).

91
Q

What is the difference between flagella in eukaryotes and prokaryotes?

A

Prokaryotes: thinner and no 9+2 arrangement. The energy to rotate the filament is provided by chemiosmosis, it is attached to the cell by a basal body with a molecular motor giving it a whip like motion.

OCR Biology AS H020 (10 decks)

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