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A Level Biology > 2.1 Cell Structure > Flashcards

2.1 Cell Structure Flashcards

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1
Q

Magnification

A

How many times bigger the image produced is than the real life object

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2
Q

Resolution

A

Ability to distinguish between objects that are close together

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3
Q

Limits of Light microscopes

A

Impossible to distinguish between 2 objects that are closer than half the wavelength of light
Cannot be used to oversee smaller organelles such as ribosomes, endoplasmic reticulum or lysosomes

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4
Q

Electron microscopes

A

Can be used to observe ribosomes, endoplasmic reticulum or lysosomes

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5
Q

How do transmission electron microscopes work

A

Focus a beam of electrons which is transmitted through the specimen, denser parts appear darker which produces contrast between different parts of the object being observed

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6
Q

Advantages of transmission electron microscopes

A

They give high resolution images, this allows internal structures within cells to be seen

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7
Q

Disadvantages of transmission electron microscopes

A

Can only be used with very thin specimens
Cannot be used to observe live specimens
Lengthy treatment required to prepare specimens means that artefacts can be introduced
Don not produce colour image

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8
Q

How do Scanning electron microscopes work

A

Scans beam of electrons across the specimen, bounces off the surface of the specimen and the electrons are detected forming an image, producing three-dimensional images that show the surface of specimens

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9
Q

Advantages of scanning electron microscopes

A

Can be used on thick specimens
Allow the external,3-d structure to be observed

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10
Q

Disadvantages of scanning electron microscopes

A

Give lower resolution than transmission electron microscopes
Cannot be used to observe live specimens
Do not produce a colour image

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11
Q

How do Laser scanning confocal microscopes work

A

Cells must be stained with fluorescent dyes, a thick section of tissue are scanned with a laser beam which is reflected by fluorescent dyes, multiple depths of the tissue are scanned to produce an image

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12
Q

Advantages of laser scanning confocal microscopes

A

Can be used on thick, 3d specimens
Allow the sterna’s, 3d structure to be observed
Very clear images are produced

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13
Q

Disadvantages of laser scanning confocal microscopes

A

It is a slow process and takes a long time to obtain an image
Laser has potential to cause photo damage to the cells

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14
Q

IAM TRIANGLE

A

Image size= actual size/magnification

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15
Q

Order of units of measurement

A

1000 nanometer= a micrometer
1000 micrometer- millimetre
1000 millimetres= metre

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16
Q

Total magnification

A

Eyepiece lens magnification x objective lens magnification

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17
Q

Comparison between electron and light microscope

A

E- large and installation means can’t be moved, L- small and easy to carry
E- vacuum needed, L- no vacuum needed
E- complicated sample prep, L- easy sample prep
E- over x500,000 magnification, L- up to x2000 magnification
E- resolution 0.5nm, L- resolution 200nm
E- specimens are dead, L- specimens can be living or dead

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18
Q

What is Cell surface membrane

A

Formed from a phospholipid bilayer, partially permeable

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19
Q

Cell wall

A

Freely permeable to most substances
Found in plant cells not animal
Outside cell membrane and offer structural support to cell
Structural support provided by polysaccharide cellulose in plants

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20
Q

Nucleus

A

Present in all eukaryotic cells (except rbc)
Relatively large and separated by cytoplasm by the nuclear envelope which has many pores
Contains chromatins which is from which chromosomes are made

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21
Q

Nuclear pores

A

Allows mRNA and ribosomes to travel out of the nucleus as well as allowing enzymes and signalling molecules to travel in

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22
Q

Mitochondria

A

Site of aerobic respiration
Surrounded by double-membrane with the inner membrane folded to form Cristal

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23
Q

Cristal

A

Matrix formed by Cristae in mitochondria contains enzymes needed for aerobic respiration, producing atp

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24
Q

Chloroplasts

A

Found in plant cells
Site of photosynthesis
Contain chlorophyll

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25
Q

Ribosomes

A

Found in all cells
Found freely in the cytoplasm of all cells or as part of the rough endoplasmic reticulum in eukaryotic cells
Site of protein synthesis

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26
Q

80s ribosomes

A

Found in eukaryotic cells

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27
Q

70s ribosomes

A

In prokaryotes, mitochondria and chloroplasts

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28
Q

Rough endoplasmic reticulum

A

Found in plants and animal cells
Surface covered in ribosomes
Formed from continuous folds of membrane continuous with the nuclear envelope
Processes proteins made by the ribosomes

29
Q

Smooth endoplasmic reticulum

A

Found in plant and animal cells
Does not have ribosomes on the surface
Involved in the production, processing and storage of lipids, carbohydrates and steroids

30
Q

Golgi apparatus structure

A

Found in plant and animal cells
Flattened sacs of membrane similar to the smooth endoplasmic reticulum

31
Q

Golgi apparatus function

A

Modifies proteins and lipids before packaging them into Golgi vesicles
Vesicles then transport the proteins and lipids to their required destination

32
Q

Large permanent vacuoles

A

A sac in plant cells surrounded by the tonoplast, selectively permeable membranes
Vacuoles in animal cells are not permanent and small

33
Q

Vesicles

A

Found in plant and animals cells
A membrane-bound sac for transport and storage

34
Q

Lysosomes

A

Specialist forms of vesicles which contain hydrologic enzymes (enzymes that break down biological molecules)
Break down waste materials such as worn-out organelles
Used extensively by cells of the immune system

35
Q

Centrioles

A

Hollow fibres made of microtubules
Two centrioles at right angles to each other form a centrosome, which organises the spindle fibres during cell division

36
Q

Microtubules

A

Found in eukaryotic cells
Makes up cytoskeleton of the cell

37
Q

Cytoskeleton

A

Used to provide support and movement of the cell

38
Q

Microvilli

A

Found in specialised animal cells
Cell membrane projections
Used to increase the surface area of the cell surface membrane in order to increase the rate of exchange of substances

39
Q

Cilia

A

Hair-like projections made from microtubules
Allows the movement of substances over the cell surface

40
Q

Flagella

A

Found in specialised cells
Similar in structure to cilia, made of longer microtubules
Contract to provide cell movement for example in sperm cells

41
Q

Structure found in only animal cells

A

Centrioles and microvilli

42
Q

Structures found in only plant cells

A

The cellulose cell wall, large permanent vacuoles and chloroplasts

43
Q

Organelles involved in protein synthesis

A

Nucleus, ribosomes, rough endoplasmic reticulum, Golgi apparatus, cell surface membrane

44
Q

Nucleus in production of proteins

A

Stores the DNA (that codes for the production of proteins) and also contains the nucleolus, which manufactures ribosomes (required for protein synthesis)

45
Q

Production of proteins 1

A

The DNA from the nucleus is copied into a molecule of mRNA via a process known as transcription

46
Q

Production of proteins 2

A

The mRNA strand leaves the nucleus through a nuclear pore and attaches to a ribosome on the rough endoplasmic reticulum

47
Q

Production of proteins 3

A

The ribosome reads the genetic instructions contained within the mRNA and uses this code to synthesise a protein via a process known as translation

48
Q

Production of proteins 4

A

This protein passes into the lumen of the rough endoplasmic reticulum to be folded and processed, cells that produce a large number of proteins eg enzyme or hormone producing cells have a extensive rough endoplasmic reticulum

49
Q

Production of proteins 5

A

The processed proteins are then transported into the Golgi apparatus in vesicles which fuses with the Golgi apparatus, releasing the proteins

50
Q

Production of proteins 6

A

The Golgi apparatus modifies the proteins, preparing them for secretion proteins that go through the Golgi apparatus are usually exported, put in lysosomes or delivered to organelles

51
Q

Production of proteins 7

A

The modified proteins then leave the Golgi apparatus in vesicles which fuse with the cell surface membrane releasing the proteins by the process of exocytosis

52
Q

Cytoskeleton structure

A

Within the cytoplasm of cells, there is an extensive network of protein fibres

53
Q

What is cytoskeleton made up of

A

Microfilaments and microtubules

54
Q

Microfilaments

A

Solids strands that are mostly made up of protein-actin. These fibres can cause some cell movement and movement of some organelles within the cells by moving against each other

55
Q

Microtubules

A

Tubular (hollow) strands that are mostly made up of the protein tubular> organelles and other cell contents are moved along these fibres using ATP to drive this movement

56
Q

Functions of cytoskeleton

A

Strengthening and support, intracellular movement, cellular movement

57
Q

Cytoskeleton- strengthening and support

A

Provides cell with mechanical strength, forming a kind of scaffolding that helps maintain the shape of the cell, supports the organelles keeping them in position

58
Q

Cytoskeleton- intracellular movement

A

Aids transport within cells by forming tracks along which organelles can move eg. Movement of vesicles

59
Q

Cytoskeleton- cellular movement

A

Enables cell movement eg, cilia and flagella, these structures are both hair-like extensions that protrude from the cell surface and contain microtubules that are responsible for moving them

60
Q

What type of cells are animal and plant

A

Eukaryotic

61
Q

What type of cells are bacteria

A

Prokaryotic

62
Q

How are prokaryotic cells different to eukaryotic cells

A

Cytoplasm lacks membrane bound organelles
Ribosomes are structurally smaller (70s) (eukaryotic(80s))
No nucleus, instead single circular DNA molecule that is free in the cytoplasm and is nt associated with proteins
A cell wall

63
Q

Three structures in prokaryotic cells that differentiate them from others

A

Plasmids, capsules and flagellum

64
Q

Plasmids

A

Small loops of DNA that are separate from main circular DNA molecules
Contain genes which can be passed between prokaryotes

65
Q

Capsule

A

Final outer layer of Prokaryotes (eg. Bacteria)
It helps protect bacteria from drying out and from attack by cells of the immune system of the host organism

66
Q

Flagellum

A

Long,tail-like structures that rotate, enabling the prokaryote to move

67
Q

Function of nucleolus

A

Produce and assemble the cells ribosomes

68
Q

Nuclear envelope

A

separates the contents of the nucleus from the cytoplasm an provides the structural framework of the nucleus

69
Q

Function of plasma membrane

A

Provides protection for the cell and provides a fixed environment inside the cell

A Level Biology (10 decks)

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