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AS Biology 9700 > Cell Structure- Topic 1 > Flashcards

Cell Structure- Topic 1 Flashcards

Definition and key points

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1
Q

Units of Measurement

A

One mm= 10^-3m
micrometre= 10^-6m
nanometre= 10^-9m

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2
Q

What features do animal and plant cells have in common

A
  • Cell surface membrane
  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Golgi apparatus
  • ER’s
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3
Q

Differences between animal and plant cells

A
  • Centrioles (A)
  • Cell walls and plasmodesmata (P)
    -Permanent vacuoles- only in plants cells (animal cells have phagocytic vacuoles)
    -Chloroplasts (P)
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4
Q

Equation for magnification

A

Observed size of image/ actual size

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5
Q

How to read the eyepiece graticule

A

First calibrate it using the stage micrometre. Place them alongside each other and look for coinciding lines. Figure out the length of 1 egu and then apply the formula.

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6
Q

Formula to find the length of a specimen

A

number of egu * calibration of one egu

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7
Q

Define resolution

A

The ability to distinguish two points that are very close together as separate

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8
Q

How do you find the limit of resolution

A

The limit of resolution is half the wavelength of the radiation used to view the sepcimen

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9
Q

How does the Transmission electron microscope (TEM) work?

A

Electrons are passed through the specimen and thus internl structures can be seen.
Only electrons that have managed to pass through the specimen are used to create the image of the specimen.

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10
Q

How does a Scanning electron microscope (SEM) work?

A

A beam of electrons is projected onto the specimen.

The image is created by the electrons that have been reflected of the surface of the specimen and so the image apears 3D
This allows fro surace sturctures to be seen

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11
Q

How are electron slides prepared? Both light and electron.

A

Light microscope specimen are coated in stains and must be alive.

Electron microscope specimen are coated in heavy metals and must be dehydrated as they are viewed in a vacuum.

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12
Q

Resolution and wavelength of radiation in a light microscope

A

Radiation used: Beams of visible light- usually violet
Wavelength 400nm
Maximum resolution: 200nm

Uses glass lenses

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13
Q

Resolution and wavelength of radiation in an electron microscope

A

Radiation used: beam of electrons
Wavelength: 0.005nm
Resolution in practice: 0.5nm

Uses electromagnetic lenses

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14
Q

What is ultrastructure?

A

The fine (detailed) structure of a cell as revealed by the
electron microscope

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15
Q

What are “False-colour” images?

A

standard black and white electron micrographs which have been altered and coloured by computers

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16
Q

Width of the cell surface membrane

A

7 nm

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17
Q

Width of the mitochondria

A

1 micrometre

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18
Q

Width of a ribosome

A

25 nm

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19
Q

what is compartmentalisation and why is it useful?

A
  • to ensure reactions do not interfere with each other
  • all organelles therefore have their own membranes ast they have their own distinct functions
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19
Q

what is ultrastructure?

A
  • detailed structures of the cell that can only be seen via an electron microscope
  • not necessarily surrounded by membranes
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20
Q

Plasmodesmata

A
  • a section in a plant cell where there is no cell wall.
    Functions- allows substances to pass
  • allows rapid transport of substance
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21
Q

cell wall

A
  • made of cellulose
  • fully permeable
  • only found in plant cells
  • provides structural support - prevents bursting and thus limits cell size
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22
Q

Vacuole

A
  • permanent vacuoles only found in plant cells
  • animal vacuoles can be phagocytic
  • surrounded by a partially permeable mebrane called tonoplast
  • stores water, ions, minerals, salts, sugars
  • also seperates waste products
  • helps maintain turgor pressure- gives turgidity
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23
Q

centrioles

A
  • they are cylindrical
    made of 9 groups of 3 microtubules
    not found in plant cells
  • involved in cell division
  • are at right angles and moves to opposite poles of the nucleus -
  • found in flagella and cilia, act as microtuble organising centres at the basal body
  • prganises microtubules
24
Q

centrosomes

A
  • pair of centrioles
  • is a MTOC
  • forms spindle microtubules (fibres) to seperate chromatids
25
Q

microtubles structure

A
  • 25 nm
    made from tubulin
    alpha and beta tubulin form dimers which then form protofilaments
  • 13 protofilamemts= 1 microtuble
  • long rigid and hollow
  • formed and broken down at MTOC’s
26
Q

microtubule function

A
  • make up the cytoskeleton
  • provides mechanical support
  • acts as an intracellular transport system for movement of vesicles
  • aid beating of flagella
  • make up spindle fibres and centrioles
27
Q

Cilia

A
  • only found in eukaryotes
  • smaller diameter than microvilli
  • makes the cell motile
  • complicated structure made of microtubles
  • used for movement (rhythimically) and locomotion
28
Q

microvilli

A
  • only found in animal cells
  • extensions of the cell surface membrane
    increase surface are fro absorption, secretion of enzymes, digestion, excretion
29
Q

centrifugation

A
  • larger structures sediment first
    nucleus, chloroplast, mitochondria, ER, plasma membranes, ribosomes
30
Q

Prokaryotes

A

include bacteria and archae
- unicellular
- relatively small (1-5 micrometer)
- simple structures
- divide by binary fission

31
Q

What do all bacteria NOT have?

A
  • no membrane bound organelles
  • no nucleus
  • DNA lies free in cytoplasm- nucleiod region
32
Q

What do ALL bacteria have

A
  • plasma membrane
  • cytoplasm
  • peptidoglycan cell wall
  • 70S ribosomes
  • circular DNA- double helix comes back to itself
  • DNA is naked- no histones associated
33
Q

What is only present in SOME proteins

A
  • plasmids
  • pili- used for sexual reproduction
  • flagellum- locomotion
  • capsule
  • mesosomes- infolding of plasm membranes (nitogen fixation or photosynthesis)
34
Q

What is common about mitochondria, chloroplasts and prokaryotes

A
  • similar size
  • small circular DNA
  • 70S ribosomes
  • divide by binary fission

endosymbiotic theory

35
Q

Which organelles have double mebranes?

A
  • nucleus
  • chloroplast
  • mitochondria

_ microtubules and ribosomes have none

36
Q

Viruses

A
  • non- cellular structure
  • not considered living
  • 20-300 nm
  • no plasma membranes, cytoplasma, ribosomes
37
Q

what 3 things to viruses have?

A
  • nucleic acid core- DNA or RNA
  • capsid- protein coat
    protective coat 1 or 2
  • some have an outer (viral) envelope of phospholipids (derived from hosts)
    some proteins may be present
38
Q

why are viruses considered non- cellular

A
  • all parasitic
  • can only reproduce by infecting living cells
  • use protein synthesising machinery of host cell to replicate
39
Q

cell surface membrane- plasma membrane STRUCTURE

A
  • 7nm thick - only electron microscope
  • tri (trilaminar) layer appearance
    partially permeable
  • made of phospholipid bilayer
40
Q

cell surface membrane FUNCTION

A
  • controls movement of substances into and out of cell
41
Q

Nucleus STRUCTURE

A
  • largest organelle
    has double membranes
42
Q

nucleus FUNCTION

A
  • contains genetic information for the synthesis of proteins
  • site of gene transcription and production of mRNA
    -DNA is protected from degration enzymes in the cytoplasm
43
Q

nuclear membrane

A

2 membranes
- have nuclear pores
attached to the ER
- controls movement of substances between the nucleus and cytoplasm

44
Q

nucleolus

A
  • densest nucleus region
  • site of ribosomeal RNA- rRNA synthesis
  • site of robosome assembly
  • chromatin DNA and its associated protein
45
Q

ribosomes

A
  • smallest organelle- 25nm
    not bound by membrane
    made of rRNA and protein
  • has 2 subunits
    can be found on the RER
  • site of protein synthesis
  • produced in the nucleolus
46
Q

types of ribosomes

A
  • 80S are 25nm and found in cytoplasmand RER of ALL eukaryotes
  • 70S are 18nm (smaller)
    found in mitichondria and chloroplasts of ALL eukaryotes
  • found in prokaryotes
47
Q

rough endoplasmic reticulum (RER)

A
  • extensive connected system of membranes
    continuoos with nuclear envelope
  • made of cisternae (flattened sacs)
  • runs through the cytoplasm
    has 80S ribosomes attached on the surface
  • site of protein synthesis and modification
  • transport protein to Golgi
48
Q

ways to modify proteins

A
  • folding
    -adding sugars
  • adding lipids
49
Q

smooth endoplasmic reticulum (SER)

A
  • Er without ribosomes
  • connected to RER
    site of lipid and steroid synthesis- eg sexual hormones
50
Q

Golgi body / apparatus /complex

A
  • made of seperate discontinuos cisternae
  • have layered appearance
  • swellings at end of sacs for vesicle formation
  • constantly being formed adn broken like that
  • formed by transport vessicles from RER on cis face
  • broken down to form secretory vesicles and lysosomes
51
Q

golgi body functions

A
  • modifucation of proteins and lipids
  • packaging molecules into vesicles for transport
  • formation of secretory vessicles for release out of cell
  • formation of lysosomes
52
Q

exocytosis

A
  • vesicle fuses with the plasma mebrane to eject substances out of cell

reverse process is endocytosis

53
Q

production and secretion of proteins

A
  • synthesis at ribosomes and RER
  • tansport vesicle from RER–> golgi body
  • modification at golgi body
  • seperation of secretory vesicle from golgi
  • vesicle fusion with plasma membrane
  • contents released via exocytosis
54
Q

Lysosomes

A
  • very samll spherical sacs
  • contain hydrolytic enzymes (lysozomes)
  • breakdown unwanted structures via hydrolysis
  • have an acidic environment
  • in WBC they digest bacteria
55
Q

mitochondria structure

A

have double membranes-large
- cristae- folded inner membrane
- matrix- interior solution
- contain 70S ribosomes and circular DNA
- divide by binary fission- HAVE PROKARYOTIC ORIGIN

56
Q

mitochondria FUNCTION

A

synthesises energy in the form of ATP
SITE OF AEROBIC RESPIRATION
- release energy

57
Q

chloroplasts structure

A
  • oval shaped
  • two membranes
  • contain chlorophyll
    thylakoid- flattened membrane sacs
    gnana is multiple thylacoid stacked upon each other
  • stroma- interior solution
  • contain 70S ribosomes, circular DNA and starch grains
  • divide by binary fission- prokaryotic origin
  • site of photosynthesis
58
Q
A

AS Biology 9700 (2 decks)

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