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Biology Y12 > cells, structure, microscopy > Flashcards

cells, structure, microscopy Flashcards

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1
Q

draw the structure and state the function of the nucleus?

A

site of DNA replication and transcription (making mRNA) and contains the genetic code for each cell

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2
Q

describe the nuclear envelope and its role

A

its a double membrane that surrounds the nucleus and it controls the entry and exit of materials and contains reactions taking place

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3
Q

what is the nuclear envelope continuous with?

A

the endoplasmic reticulum

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4
Q

describe the nuclear pores and its role within the nucleus

A

has 3000s pores per nucleus, each 40-100nm in diameter and it allows the passage of large molecules such as mRNA

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5
Q

describe the nucleolus and its role?

A

it makes ribosomal RNA and assembles ribosomes. may be more than 1 nucleolus in a nucleus

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6
Q

describe the nucleoplasm and its role within the nucleus

A

granular, jelly-like substance that makes up the bulk of the nucleus

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7
Q

desribe the chromosomes and its role within the nucleus

A

found in nucleus, protein-bound linear DNA

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8
Q

draw the structure and state the function of the mitochondria

A

site of aerobic respiration, site of ATP production and where DNA codes for enzymes needed in respiration

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9
Q

describe the mitochondria

A

usually rod-shaped 1-10nm in length

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10
Q

explain the mitochondrias double membrane and its role

A

has an outer and inner membrane that controls the entry and exit of materials

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11
Q

describe the cristaes?

A

the inner membrane is folded to make cristae. which can extend across the whole width of the mitochondrion

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12
Q

describe the cristaes role in the mitochondria

A

provides a large SA for attachment of enzymes and other proteins involved in respiration

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13
Q

describe the matrix and its role in the mitichondrion?

A

contains proteins, lipids, ribosomes and DNA that allow the mitochondria to control production of own proteins. many enzymes involved in respiration are found in the matrix

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14
Q

draw and state the function of chloroplasts

A

main site of photosynthesis

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15
Q

describe the role of the double membrane in the chloroplasts

A

the double plasma membrane surrounds the organelle it is highly selctive in what it allows to enter/exit the chloroplasts

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16
Q

describe the thylakoids and its role?

A

thylakoids contain a green pigment (chlorophyll). some thylakoids have tubular extensions that join up with thylakoids in adjacent grana

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17
Q

describe the grana and its role?

A

stacks of 100 disc-like structures called thylakoids where 1st stage of photosynthesis takes place (light absorbtion)

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18
Q

describe the stroma and its role?

A

fluid filled matrix where 2nd stage of photosynthesis takes place (synthesis of sugars) and contains enzymes to make sugars for photosynthesis

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19
Q

why do granal membranes have a large SA?

A

for attachment of enzymes, chlorophyll and electron carriers

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20
Q

why do chloroplasts contain both DNA and ribosomes?

A

quickly make proteins needed for photosynthesis

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21
Q

draw and state the function of the rough endoplasmic reticulum

A

Packages transports modified proteins

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22
Q

describe the ribosomes and its role within the RER?

A

ribosomes are present on the outer membrane. they provide a large SA for synthesis of proteins and glycoproteins also provide a pathway for the transport of materials especially proteins throughout the cell.

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23
Q

what are the cisternae?

A

folded memebranes

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24
Q

draw and state the function of the smooth endoplasmic reticulum

A

synthesises, stores and transports lipids and carbohydrates

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25
Q

describe the structure of the SER

A

folded membranes-cisternae, no ribosomes

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26
Q

what type of cells have lots of SER and RER

A

secretory cells e.g epithelial and liver cells

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27
Q

when are lysosomes formed?

A

when the vessicles produced by the golgi contain enzymes such as protease and lipases

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28
Q

draw state each function of the lysosome?

A
  • hydrolyse material injested into cellels
  • release enzymes to the outside of the cell (exocytosis) to destroy material around cell
    -digest worn out organelles so that the useful chemicals theyre made out of can be reused
  • completely break down cells after they have died (autolysis)
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29
Q

describe the lysosome and the enzymes within

A

lysosomes contain lysozymes enzymes that hydrolyse the cell wall of certain bacteria

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30
Q

how many enzymes can be in a lysosome?

A

as many as 50

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31
Q

lysosmes are abundant in…?

A

secretory cells

32
Q

draw and state the many functions of the golgi

A
  • add carbohydrates to proteins to form glycoproteins
  • produce secretory enzymes
  • secret carbohydrates
  • transport, modify store lipids
  • form lysosomes
33
Q

how are proteins passed through the golgi apparatus?
stage 1:

A

the proteins and lipids are passed through golgi apparatus through a strict sequence

34
Q

stage 2 :golgi

A

the golgi modifies the proteins often adding other components e.g carbohydrates

35
Q

stage 3:golgi

A

then labels them allowing them to be sent to their accurate destinations

36
Q

stage 4: golgi

A

once sorted modified proteins and lipids are transported to golgi vessicles

37
Q

stage 5 : golgi

A

these vesicles may move to their cell surface where they fuse with the membrane and release contents

38
Q

in which cells are the golgi especially well developed in?

A

secretory cells

39
Q

draw and describe the function of the ribosomes?

A

site of protein synthesis

40
Q

what are ribosomes made up of?

A

protein and ribosomal RNA

41
Q

describe the larger version of ribosomes?

A
  • 80s
  • found in eukaryotic cells
    -around 25nm in diameter
42
Q

describe the smaller version of ribosomes?

A
  • 70s
  • found in prokaryotic cells, mitochondria, chloroplast
    -much smaller
43
Q

draw and state the function of the cell wall?

A

to provide mechanical/structural strength in order to prevent cells bursting under the pressure created by osmosis

44
Q

describe the features of the cell wall and their roles?

A

in plant cells- made of microfibrils of polysaccharide cellulose
in animal cells - made up of chitin polysaccharide of nitrogen
- thin layer called middle lamella marks the boundry between adjacent cell walls and cements them together

45
Q

draw and state the function of the vacoule?

A
  • support herbaceous plants /woody plants by making cells turgid
    -act as temporary stores of sugar and amino acids
    -these pigments may colour petals to attract pollinating insects
46
Q

describe the structure of the vacoule

A

Filled with fluid surrounded by a single membrane tonoplast

47
Q

draw and state the function of the Tonoplast

A

Single membrane controls the exit and entry of materials

48
Q

What is cell fractionation?

A

A means of studying different parts of a cell and investigating the function of organelles

49
Q

What is homogenisation?

A

1st stage in cell fractionation it breaks open the cell/ releases organelles

50
Q

Explain the homogenisation process?

A
  1. Cells are broken up by the homogenizer which releases organelles.
  2. Resistant fluid homeganate is then filtered to remove insoluble tissue and cellular debris
51
Q

Before homegenation why does the tissue need to be placed into an ice cold isotonic buffer?

A
  1. Ice cold - slows down enzyme activity
  2. Isotonic - prevents shrinking or bursting of organelles by osmosis
  3. Buffer - prevents change in pH which would effect enzymes
52
Q

Why do we need to filter our homogenate?

A

May contain cellular debris that has equal density as organelles

53
Q

What is ultracentrifugation?

A

2nd stage of cell fractionation where homogenate is spun to separate organelles in a centrifuge

54
Q

Explain how ultracentrifugation works
a.k.a differential centrifugation?

A
  1. The tube of filtrate is placed in a centrifuge and spun at a low speed
  2. The heavier more dense organelles is forced to the bottom of the tube forming a thin sediment pellet
  3. The fluid (supernatent) is removed/transferred into another tube , leaving just the sediment of the nuclei
  4. The remaining super agent is spun again at a faster speed where this time the sediment pellet formed contains the mitochondria
  5. This process is repeated by increasing the speed to remove the next dense/ heavier organelles
55
Q

What type of cell is a bacteria cell?

A

Prokaryotic cell

56
Q

What are the properties of prokaryotic cells?

A

Smaller cells, no membrane bound organelles, no nucleus cell wall made of murein

57
Q

Draw structure of a prokaryote
The cell wall is made of…

A

Peptidoglycans (murein) rather than cellulose

58
Q

Function of the cell wall?

A

Prevents bursting in hypertonic surroundings, maintains shape

59
Q

What is the cell membrane and it’s role?

A

A double phospholipid layer which controls the passage of substances into and out of the cell

60
Q

What is the nuclear zone and its function?

A

Folded/circular tight mass of DNA and RNA ,usually a singular strand contains nucleus acid with genetic information

61
Q

What are ribosomes and explain their role in prokaryotes?

A

70s ribosomes main site of protein synthesis (translation)

62
Q

What may some bacteria contain?

A

Plasmid , capsule and flagella

63
Q

What is the flagella and it’s function?

A

A long fine projection made of the contractile protein called flagellin. responsible for locomotion, can be from one end of the cell or several around the cell

64
Q

What are plasmids and their function?

A

Self- replicating small loops of DNA. Can be transferred between cells often responsible for antibiotic resistance transferral, useful in genetic engineering

65
Q

What is the capsule and it’s function?

A

Made up of polysaccharides , protection against wbc, antibodies and other harmful environmental factors. also enables attachment to other objects

66
Q

Explain how a light microscope works?
Illuminated by:
Focused by:
Maximum magnification:
Resolving power:
Specimens dead or living:
Specimen thickness:
Ease of preparation:
Cost of equipment:
Images colour:
Image dimension:

A
  • Illuminated by light
  • Focused by glass lenses
  • x1500
  • 200nm (can see cells but not details of organelles)
  • both
  • thin
  • easy
  • cheap
  • coloured images
  • 2D
67
Q

Explain how a transmission electron microscope works?
Illuminated by:
Focused by:
Maximum magnification:
Resolving power:
Specimens dead or living:
Specimen thickness:
Ease of preparation:
Cost of equipment:
Images colour:
Image dimension:

A
  • illuminated by a beam of electron
  • focused by a condenser magnet
  • x500,000
  • 0.1nm or 1nm
  • both
  • had to be really thin to allow electrons to penetrate
  • difficult
    -expensive
  • black and white
  • 2D
68
Q

Why does the specimen appear darker or brighter in some areas?

A

Parts of the specimen that appear dark absorb electrons whereas the parts of the specimen which appear lighter allow electron to pass through it

69
Q

Explain how a scanning electron microscope works?
Illuminated by:
Focused by:
Maximum magnification:
Resolving power:
Specimens dead or living:
Specimen thickness:
Ease of preparation:
Cost of equipment:
Images colour:
Image dimension:

A
  • illuminate by a beam of electrons
  • focused by an electron magnet
  • x500,000
  • 20nm
  • specimen must be dead
  • thin but not as thin as TEM
  • difficult
  • expensive
  • black and white
    -3D
70
Q

Limitations of SEM and TEM?

A
  • whole system has to be in a vaccum so living specimens cannot be observed
  • complex ‘staining’ process required yet image is still not coloured
  • specimen must be extremely thin (TEM)
  • the image may contain artefacts
71
Q

What’s the difference between SEM and TEM?

A

The SEM directs a beam of electrons onto surface of specimen from above whereas TEM a beam of electrons is penetrating it from above

72
Q

Advantages of the electron microscope

A
  • electron beam has a shorter wavelength so it has a higher resolution
  • electrons are negatively charged so can be focused by an electromagnet
73
Q

What is an eyepiece graticule?

A

A disc which allows the size of the specimen to be observed

74
Q

What is an important rule of the eyepiece graticule?

A

The scale of the eyepiece graticule remains constant no matter what magnification the cells are viewed at

75
Q

What is meant by the term calibration?

A

Fixing know points and constructing a scale between them

76
Q

To calibrate an eyepiece graticule what do we use..?
What does a stage micrometer show?

A
  • a special microscope slide - stage micrometer
  • true lengths
77
Q

DONE!!

A

Biology Y12 (20 decks)

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