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AS Biology > Cell Structure > Flashcards

Cell Structure Flashcards

structure of eukaryotes, structure of prokaryotes & viruses, methods of studying cells & all cells arise from other cells

1
Q

What are eukaryotes and prokaryotes?

A

Eukaryotic: DNA is contained in a nucleus, contains membrane-bound specialised organelles e.g. plant, animal and fungi
Prokaryotic: DNA is ‘free’ in cytoplasm, no organelles e.g. bacteria and archaea

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2
Q

Structure of the Nucleus?

A
  • large membrane-bound organelle, surrounded by nuclear envelope which contains many pores
  • nucleus contains chromosomes and 1 or more structure called a nucleolus (assembles cell’s ribosomes)
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3
Q

The function of a nucleus?

A
  • houses the cell’s genetic material/DNA, and is also the site of synthesis for ribosomes (nucleolus) = the cellular machines that assemble proteins
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4
Q

Structure of the cell-surface membrane?

A
  • found on the surface of animal cells and just inside cell wall of others (plants)
  • phospholipid bilayer with intrinsic and extrinsic proteins
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5
Q

Function of the cell-surface membrane?

A
  • regulates movement of substances in and out of cell

- also has receptor molecules on it, which allow it to respond to chemicals like hormones

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6
Q

Structure of mitochondrion?

A
  • oval shaped

- double membrane (inner one folded to form cristae and inside is matrix which contains enzymes involved in respiration)

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7
Q

Function of mitochondrion?

A
  • site of aerobic respiration, where ATP is produced

- Found in large numbers in cells that are v actice and require a lot of energy

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8
Q

Structure of the Golgi Apparatus?

A
  • group of membrane-bound fluid-filled flattened sacs

- vesicles are often seen at edge of sacs

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9
Q

Function of Golgi Apparatus?

A
  • processes and packages new lipids and proteins.

- also makes lysosomes

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10
Q

Structure of Golgi Vesicle?

A
  • membrane-bound

- small fluid-filled sac in cytoplasm, and produced by golgi apparatus

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11
Q

The function of Golgi vesicle?

A
  • stores lipids and proteins made by the Golgi apparatus and transports them out of the cell (via cell-surface membrane)
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12
Q

Structure of the lysosome?

A
  • type of golgi vesicle
  • round organelle surrounded by membrane
  • no clear internal structure
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13
Q

Function of the lysosomes?

A
  • contains lysozymes (digestive enzymes)
  • lysozymes kept separate from cytoplasm by surrounding membrane
  • can be used to digest invading cells or break down worn-out components of cell
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14
Q

Structure of ribosomes?

A
  • very small organelle that floats freely in cytoplasm or is attached to rough endoplasmic reticulum
  • made up of proteins and RNA
  • not surrounded by a membrane
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15
Q

Function of ribosomes?

A
  • site where proteins are made
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16
Q

Structure of rough endoplasmic reticulum (RER) ?

A
  • a system of membranes enclosing a fluid-filled space

- surface covered w ribosomes

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17
Q

Function of rough endoplasmic reticulum (RER) ?

A
  • folds and processes proteins that have been made at the ribosomes
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18
Q

Structure of smooth endoplasmic reticulum (SER) ?

A

similar to RER but no ribosomes

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19
Q

Function of SER?

A

synthesizes and processes lipids

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20
Q

Structure of chloroplast?

A
  • small, flattened structure found in plants and algal cells
  • surrounded by double membrane
  • Inside the chloroplast are stacks of thylakoids, called grana, as well as stroma, the dense fluid inside of the chloroplast
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21
Q

Purpose of thylakoids

A
  • thylakoids contain chlorophyll (which absorbs light) that is necessary for the plant to go through photosynthesis
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22
Q

Function of chloroplast?

A
  • site of photosynthesis takes place

- some parts happen in the grana and others in the stroma (thick fluid)

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23
Q

Structure of the cell wall?

A
  • rigid structure that surrounds cells in plants and fungi
  • in plants/algae it’s made mainly of cellulose
  • in fungi, it’s made of chitin (polysaccharides)
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24
Q

Function of cell wall?

A
  • provides strength to the cell, which helps protect the cell against physical damage
  • prevents it from changing shape
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25
Q

Structure of cell vacuole?

A
  • membrane-bound organelle found in cytoplasm of plant cells
  • contains cell sap - weak solution of sugars & salts
  • surronding membrane called tonoplast
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26
Q

What is tonoplast?

A
  • cytoplasmic membrane surrounding the vacuole

- separating the vacuolar contents from the cytoplasm in a cell

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27
Q

Function of the vacuole?

A
  • helps maintain pressure inside cell and keep cell rigid, stops plant wilting
  • also involved in isolation of unwanted chemicals inside the cell
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28
Q

Organelles that plant cells contain & others don’t?

A
  • cellulose cell wall with plasmodesmata (‘channels’ for exchanging substances with adjacent cells)
  • vacuole (compartment that contains cell sap)
  • chloroplast
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29
Q

Name the parts of a bacteria cell

A
  • cytoplasm
  • plasma membrane
  • cell wall
  • capsule
  • plasmids
  • circular DNA
  • flagellum (pl. flagella)
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30
Q

How are specialized cells organized?

A

into tissues, tissues into organs & organs in organ systems
e.g.
tissue - muscle tissue
organs - animal heart
organ systems - female reproductive system - includes uterus, ovaries, mammary glands & breasts

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31
Q

Compare prokaryotes and eukaryotes

A
  • prokaryotic cells are smaller
  • prokaryotic cells are unicellular, eukaryotic cells are often multicellular
  • prokaryotic cells have no nucleus or membrane, eukaryotes have nucleus & membrane-bound organelles
  • in prokaryotes, DNA is circular w/o proteins, in eukaryotic cells DNA linear & associated with protein to form chromatin
  • in prokaryotes, cell division by binary fission, in eukaryotes cell division is by mitosis or meiosis
  • in prokaryotes reproduction is asexual, in eukaryotes, it’s sexual or asexual
  • in prokaryotes there’s a huge variety of metabolic pathways but common metabolic pathways for eukaryotes
  • in prokaryotes ribosomes are small (70S), in eukaryotes ribosomes are large (80S)
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32
Q

Cells of prokaryotes and eukaryotes?

A
  • prokaryotes are simple, single-celled organisms

- eukaryotes are complex multicellular organisms

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33
Q

Examples of eukaryotes?

A

animal, plant, fungi and algae cells

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34
Q

Example of prokaryotes?

A

Bacteria

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35
Q

What kind of organism are viruses?

A

Acellular, they’re not cells

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36
Q

How do viruses replicate?

A
  • being non-living, viruses don’t undergo cell division

- they use host cells to replicate themselves

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37
Q

Describe how Viruses Replicate

A
  • viruses use host cells
  • use their attachment protein to bind to complementary receptor proteins on the surface of host cells (different viruses have different attachment proteins)
  • inject their own DNA (or RNA) into host cell, which provides instructions for metabolic processes of host cell to produce viral components, which are then assembled into new viruses
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38
Q

Describe the structure of a virus

A
  • smaller than bacteria
  • contains nucleic acids (e.g, DNA or RNA) as their genetic material
  • attachment proteins vital for virus to identify and attach to host cell
  • nucleic acid enclosed within protein called CAPSID
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39
Q

Describe Mitosis cell structure practical (RP 2)

A
  • cut root tip (e.g. from onion)
  • put root tip in HCl (1 mol dm-3) and in water bath (60 degrees C)
  • rinse root tip w/ cold water and dry/blot
  • place on microscopic slide (2mm of tip) and spread w/ mounted needle
  • Add a stain (touidine blue O) to see cells
  • place cover slip on top to sqaush cells
  • place under microscopic microscope
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40
Q

Give 3 controlled variables to ensure similar root growth in plants (with reasons) in mitosis practical

A
  • all plants of same age (so same time for cell divisions)
  • all plants given same watering (so same amount of water for cell expansion)
  • all plants given same light (same rate of photosynthesis)
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41
Q

Why is a root tip used in mitosis practical?

A

it’s where mitosis occurs

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42
Q

why is a stain used in mitosis practical?

A

to distinguish chromosomes - not visible w/o stain

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43
Q

why is root tip firmly squashed?

A

make tissue thinner and allow light to pass through it

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44
Q

What could make results different from others in mitosis practical?

A
  • temp
  • age of root tip
  • chance
  • genetic differences / different type of onion (or garlic)
  • water availability
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45
Q

Is interphase part of mitosis?

A

No

46
Q

Why is mitosis needed?

A
  • growth of multicellular organisms

- repairing damaged tissues

47
Q

What happens in mitosis?

A

parent cell divides to produce two genetically identical daughter cells

48
Q

What happens in the cell cycle?

A
  • consists of a period of cell growth and DNA replication called interphase
  • Mitosis happens after that
49
Q

Interphase is subdivided into what?

A
  • 3 separate growth phases
    G1 gap phase 1
    S synthesis
    G2 gap phase 2
50
Q

What happens in Gap phase 1?

A

cell grows and new organelles & proteins made

51
Q

What happens in synthesis?

A

cell replicates it’s DNA, ready to divide by mitosis

52
Q

What happens in Gap phase 2?

A

cell keeps growing & proteins needed for cell division are made

53
Q

What is mitotic index?

A

proportion of cells in a population undergoing mitosis

54
Q

How do you calculate mitotic index?

A

cells undergoing mitosis (P+M+A+T)/ total no. of cells (I+P+M+A+T) X 100

55
Q

How is a tumor formed?

A
  • if mutation occurs in gene that controls cell division, cells can grow out of control
  • cells keep dividing to make more & more cells to form a tumour
56
Q

What’s a tumor?

A

a group of abnormal cells

57
Q

What is cancer?

A

a tumour that invades surrounding tissue

58
Q

How do drugs used to treat cancer (chemotherapy) work

A
  • by disrupting the cell cycle:
  • preventing DNA from replicating
  • inhibiting metaphase stage by interfering with spindle formation
59
Q

The issue with drugs used to treat cancer?

A
  • the drugs also disrupt cell cycle of normal cells
60
Q

What happens in interphase?

A
  • DNA replicates in cell

- and chromosomes become visible

61
Q

What happens in prophase?

A
  • chromosomes condense getting shorter & fatter - stay together due to CENTROMERES
  • Nuclear envelope disintegrates
  • Nucleolus disappears
62
Q

What happens in metaphase?

A
  • spindle forms

- chromosomes line up on centre of the cell

63
Q

What happens in anaphase?

A
  • spindle fibres attached to CHROMATIDS contract

- chromatids are pulled towards opposite poles of cell

64
Q

What happens in Telophase

A
  • cytoplasm begins to divide & nuclear envelope reforms
  • spindle fibres disintegrate and cytoplasm dividesin CYTOKINESIS
  • so 2 genetically identical daughter cells formed
65
Q

Differences between meiosis and mitosis

A
  • Mitosis produces diploid cells, meiosis produces haploids cells
  • Mitosis produces genetically identical daughter cells, meiosis produces genetically different daughter cells
  • Mitosis produces 2 daughtr cells, meiosis produces 4
66
Q

Random Q: What 2 things give meiosis genetic variation?

A
  • independent assortment

- crossing over

67
Q

Describe the process of binary fission?

A
  • circular plasmid loops replicated lots & Circular DNA strand replicated once
  • DNA loops drawn to opposite poles of cell
  • cytoplasm divides, new cell walls begin to form
  • 2 new daughter cells formed and have 1 copy of circular DNA but variable no. of copies of plasmids
68
Q

Describe the ribosome in a bacterial cell

A
  • smaller than those in eukaryotes
69
Q

Describe the circular DNA in a bacterial cell

A
  • possesses genetic info for replication of bacterial cells
70
Q

Describe the cell wall in bacterial cells

A 
- made up of MUREIN - polymer of polysaccharides
and peptides (It's a glycoprotein)
- acts as a physical barrier that protects bacteria
71
Q

Describe the capsule in bacterial cells

A
  • bacteria protect themselves by secreting capsule of mucilaginous SLIME around this wall
72
Q

Describe the cells surface membrane in a bacterial cell?

A
  • made up of lipids & proteins

- controls movements of substances in & out of cell

73
Q

Describe the plasmid in a bacterial cell?

A
  • small loops of DNA
  • possesses genes that may aid survival of bacteria in adverse conditions e.g. produces enzymes that break down antibiotics
74
Q

Describe the flagellum in a bacterial cell?

A
  • long hair like structure

- rotates to make prokaryotic cells move

75
Q

What is magnification?

A

how many times larger the image is compared to the object
mag = image size/ actual size
(I AM)

76
Q

What’s resolution?

A

-ability of a microscope to distinguish 2 adjacent structures as separate

77
Q

What does a high resolution result in?

A
  • better clarity and detail of the image
78
Q

Name the two types of microscopes

A
  • optical (light) microscopes

- electron microscopes (SEM and TEM)

79
Q

How does an optical microscope work?

A

Light focused on small area of thin specimen
Lenses magnify image

(individual cells usually transparent and so coloured w/ special stains to make distinguishable)

80
Q

Specimen in optical microscope:

A

can be alive

81
Q

What does staining do to cells in optical microscopes?

A

kills them

82
Q

Max resolution and magnification of optical microscopes?

A

0.2 micrometres

x 1500 mag

83
Q

What can be seen in optical microscope?

A

Nucleus and mitochondria

84
Q

How does Electron microscope work?

A
  • uses beam of electrons instead of beam of light

- this allows for high magnfication & resolving power (resolution)

85
Q

Max resolution and magnification of electron microscopes?

A

0.002 micrometres

x 150, 0000 mag

86
Q

What does SEM and TEM stand for?

A
  • Scanning electron microscopes

- Transmission electron microscopes

87
Q

Describe scanning electron microscopes

A
  • a beam of electrons passes
    across the surface and scatter.
  • the pattern of scattering builds up a 3D image depending on the contours of the specimen
88
Q

Two differences between SEM and TEM

A
  • specimens in SEM do not have to be thin like in TEM

- Resolution is lower in SEM than in TEM

89
Q

Describe Transmission electron microscopes

A
  • elecron beam penetrates cells & provide detail of cell’s internal structures
90
Q

What do TEMs use?

A
  • electromagnets to focus electron beam (they’re high resolution microscopes)
91
Q

Advantage of TEM?

A

High resolution so can see internal structures of organelles like chloroplast

92
Q

What’s the point of cell fractionation?

A
  • separates organelles according to size to allow them to be studied in an electron microscope
93
Q

Stages of cell fractionation

A
  • Homogenisation
  • Filtration
  • Ultracentrifugation
94
Q

What happens in homogenisation?

A
  • tissue sample blended (homogenised) using blender to break cells under specific conditions
95
Q

Specific conditions of homogenisation and why?

A
  • ice cold (reduces enzyme activity that might damage organelles)
  • isotonic solution (prevents osmosis that could shrink or burst organelles - no osmosis takes place in isotonic solution)
  • buffered solution (avoids damaging protein structures)
96
Q

What happens in filtration of cell fractionation?

A
  • tissue sample filtered into gauze - gauze separates large components from small organelles
  • organelles filtered into tubes to be fractionated using ultracentrifugation
97
Q

What happens in ultracentrifugation of cell fractionation?

A
  • sample spun at low speed in a centrifuge
  • each tube balanced w/ another tube directly opposite for centrifuge to work properly
  • cell debris (e.g. cell walls) forms pellet at bottom of tube, leaving supernatant (a liquid) above it that contains the organelles
  • supernatant poured off & centrifuged at higher speed to separate next heaviest organelles
  • repeated as increasingly higher speeds to separate each fraction
98
Q

What does centrifugation do?

A
  • centrifuge spearates sample into fractions (heavier organelles forced to bottom of tube, lighter organelles move towards top)
99
Q

Last process of centrifugation?

A
  • supernatant poured off & centrifugation at higher speed to separate next heaviest organelles
  • repeated as increasingly higher speeds to separate each fraction
100
Q

Heaviest to lights organelles:

A
  • Nucleus
  • Chloroplasts
  • ER
  • mitochondria
  • lysosomes
  • ribosomes
101
Q

Limitations of TEM?

A
  • whole system must be in a vacuum therefor living organisms can’t be observed
  • specimen must be extremely thin
  • image may contain artefacts (things that result from the way the specimen is prepared)
  • complex staining process required & even then image not in colour
102
Q

What’s a graticule?

A
  • glass disc that is placed in eyepiece of microscope
  • scale etched onto glass disc
  • scale typically 10 mm long with 100 sub-divisions
  • scale visible when looking down eyepiece of a microscope
103
Q

How to calibrate a graticule?

A
  • Place a stage micrometer on the stage of the microscope
  • line up one of the divisions on the eyepiece graticule with a fixed point on the stage micrometer.
  • count number of divisions on eyepiece graticule that correspond with a set measurement on stage micrometer
  • Calculate the distance in micrometres of one division on the eyepiece graticule.
104
Q

Conversions of millimetre to micrometer

A

divide by 1000

105
Q

Types of measurements/ units?

A

millimetres, micrometres, nanometres

106
Q

Compare and contrast DNA in eukaryotic cells and prokaryotic cells

A
  • DNA in mitochondria/chloroplast similar (structure) to DNA in prokaryotes
  • Eukaryotic DNA is linear
  • Eukaryotic DNA contains introns, prokaryotic DNA doesn’t
  • Eukaryotic DNA is linear, prokaryotic DNA circular
  • Eukaryotic DNA is associated with proteins/histones, prokaryotic DNA is not
107
Q

State 1 way to calculate the area of a plant leaf

A
  • draw around leaf on graph paper and count squares
108
Q

contrast how an optical microscope and a transmission electron microscope work

A
  1. TEM use electrons, optical uses light
  2. TEM allows greatER resolution
  3. so, with TEM smaller organelles can be observed
  4. TEM can only view dead/dehydrated specimens and optical can be observed
  5. TEM doesn’t show colour and optical can
  6. TEM requires thinnER specimen
  7. TEM requires a more complex/time-consuming preparation
  8. TEM focuses using magnets and optical (glass) lenses
109
Q

suggest ways to improve the quality of a scientific drawing

A
  • don’t use shadowing
  • don’t use sketching/use single lines
  • add (more) annotations
  • don’t cross label lines
  • add magnification/scale (bar)
110
Q

Describe how you would use cell fractionation techniques to obtain a sample of chloroplasts from leaf tissue. Do not include in your answer information about any solutions.
[3 marks]

A
  1. Macerate / homogenise / blend / break tissues
    / cells (in solution);
  2. Centrifuge;
  3. At different / increasing speeds until
    chloroplast fraction obtained;
111
Q

Give three structures found in the prokaryotic cells but not in the eukaryotic cells

A

Plasmid DNA
flagellum
capsule

112
Q

How would you calculate the number of cells produced by mitosis

A

No (Number of cells beginning with) x 2n (2 to the power of ‘the number of divisions’)

e.g. bacteria culture of 3 cells underwent 6 cell divisions. Assuming no deaths to limiting factors, calculate the number of cells in the culture after the division
3 x 2(power of 6) = 192 cells

AS Biology (9 decks)

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