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Biology Module 2 > 2.1 Cell Structure > Flashcards

2.1 Cell Structure Flashcards

Cell Structure

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1
Q

what are 2 types of organelles

A

prokaryotic and eukaryotic

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2
Q

what are organelles

A

parts of cells, each with a specific function

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3
Q

name parts of animal cell

A

nucleus
nucleolus
nuclear envelope
plasma (cell surface) membrane
rough/smooth endoplasmic reticulum
lysosome
ribosome
Golgi apparatus
cytoplasm
mitochondrion

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4
Q

name additional parts of plant cell

A

chloroplast
vacuole
cell wall
plasmodesma

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5
Q

plasma (cell surface) membrane

A
  • membrane found on surface of animal cells and just inside cell wall of plant and prokaryotic cells
  • mainly made of lipids and protein
  • regulates movement of substances in and out of cell
  • has receptor molecules on it, allowing it to respond to chemicals like hormones
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6
Q

cell wall

A
  • rigid structure that surrounds plant cells
  • made of carbohydrate cellulose
  • supports plant cell
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7
Q

nucleus

A
  • large organelle
  • surrounded by (double membrane) nuclear envelope, which contains many pores
  • contains chromatin, made of DNA and proteins
  • contains structure called nucleolus
  • controls the cell’s activities (by controlling the transcription of DNA ( DNA contains instructions to make proteins))
  • pores allow substances to move through the nucleus and to cytoplasm
  • nucleolus makes ribosomes
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8
Q

lysosome

A
  • round organelle surrounded by membrane
  • no clear internal structure
  • contains digestive enzymes (kept separate from cytoplasm via membrane)
  • digest invading cells
  • break down worn out components of the cell
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9
Q

ribosome

A
  • very small organelle
  • float freely in cytoplasm/ attached to RER
  • made of proteins and RNA
  • not surrounded by membrane
  • large and small sub-unit
  • site where proteins are made
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10
Q

rough/smooth endoplasmic reticulum

A
  • system of membranes enclosing a fluid filled space
  • rough: surface covered with ribosomes
  • rough: folds and processes proteins that have been made at the ribosomes
  • smooth: synthesises and processes lipids
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11
Q

vesicle

A
  • small fluid filled sac in the cytoplasm
  • surrounded by membrane
  • transports substances in and out of cell (via plasma membrane) and between organelles
  • formed by GA or ER, others at cell surface
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12
Q

Golgi apparatus

A
  • group of fluid-filled, membrane-bound flattened sacs
  • often see vesicles at the edge of these sacs
  • processes and packages new lipids and proteins
  • makes lysosomes
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13
Q

mitochondrion

A
  • oval shaped
  • double membrane
  • inner membrane folded to form structure called cristae
  • inside is matrix, containing enzymes involved in respiration
  • site of aerobic respiration (where ATP is produced)
  • found in large numbers in active cells where lots of energy is required (e.g. secretory cells that are metabolically active)
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14
Q

chloroplast

A
  • small flattened structure found in plant cells
  • surrounded by double membrane
  • has membranes inside called thylakoid membranes
  • membranes are stacked up in some parts to form grana
  • grana are linked by lamellae ( thin, flat pieces of thylakoid membrane)
  • site of photosynthesis
  • happens in grana
  • happens in stroma (thick fluid inside)
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15
Q

centriole

A
  • small, hollow cylinders made of microtubules (tiny protein cylinders)
  • found in animal cells, but only some plant cells
  • involved in separation of chromosomes during cell division
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16
Q

flagellum

A
  • on eukaryotic cells, are like cilia but longer
  • stick out from cell surface and are surrounded by plasma membrane
  • 9 + 2 formation too
  • microtubules contract to make the flagellum move
  • used like outboard motors to propel cells forward
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17
Q

cilia

A
  • small hair like structure found on the surface membranes of some animal cells
  • in cross section, have outer membrane and ring of 9 microtubule pairs inside, with two in the middle (9+2 formation)

-microtubules allow cilia to move
- used to move substances along the cell surface

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18
Q

difference between proteins made with free floating ribosomes and RER ribosomes

A

free floating: endocellular proteins, stay within the cytoplasm
RER: exocellular proteins, excreted or attached to cell membrane

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19
Q

protein production

A

DNA stored in nucleus, and gene codes for a particular protein
1) single strand copy of gene is made out of RNA, called mRNA (DNA too big and precious to leave nucleus and get damaged)
2) mRNA leaves nucleus via nuclear pore
3) travels to ribosome on RER through cytoplasm
4) ribosome reads code on mRNA to build protein out of amino acid
5) protein travels through fluid filled sacs of RER ( cisternae) until reaches end (e.g. to add sugar chains), and is pinched off in a vesicle
6) travels and fuses to GA, where is modified (e.g. sugar chains added or trimmed) and packaged into another vesicle ready for export
7) travels to cell surface membrane, where fuses and protein is released via exocytosis

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20
Q

what is the cytoskeleton?

A

network of protein threads running through the cytoplasm (solution of chemicals)

21
Q

what is the cytoskeleton arranged as in eukaryotes

A

microfilaments - small solid strands made of actin
microtubules - tiny protein cylinders made of tubulin which polymersises

22
Q

what are the 4 main functions of the cytoskeleton

A
  • support
  • strengthen + maintain shape
  • movement of materials within cell
  • movement of cell itself
23
Q

explain the functions of the cytoskeleton

A

1) the microtubules and microfilaments support the cells organelles, keeping them in position
2) they help strengthen the cell and maintain its shape

3) they’re responsible for the movement of materials within a cell. e.g. the movement of chromosomes when they separate during cell division depends on the contraction of microtubules in the spindle

4) proteins of the cytoskeleton can also cause the cell to move. e.g. movement of the cilia and flagella is caused by cytoskeletal protein filaments that run through them. ( in single cells that have flagellum, the cytoskeleton propels the whole cell)

24
Q

what is meant by “dynamic” when describing the cytoskeleton

A

constantly changing
allows it to respond to changes in the cell and carry out its function

25
Q

compare prokaryotic and eukaryotic cells

A
  • extremely small (0.1-10 micrometers)
  • larger cells (10-100 micrometer)

-DNA is circular (coiled chromosome)
-DNA is linear

-no nucleus, DNA is free in the cytoplasm
-nucleus is present, with DNA inside

  • cell wall made of polysaccharide peptidoglycan
    -no cell wall in animals, cellulose in plants and chitin in fungus

-few organelles and no membrane bound organelles
-many organelles including membrane bound ones like mitochondria

  • flagella when present is made of protein flagellin, arranged in a helix
    -flagella when present is made of microtubules arranged in a “9+2” formation
  • small 70S ribosomes
  • larger 80S ribosomes
26
Q

characteristics of prokaryotic bacteria

A
  • DNA (bacterial chromosome)
  • plasma (cell surface) membrane
  • cell wall
  • plasmid (ring of DNA)
  • ribosome
  • flagellum (tail used to propel the cell)
27
Q

how would you be able to see a prokaryotic cell

A
  • roughly tenth the size of eukaryotic cells
  • normal microscopes not powerful enough to look at their internal structures
  • seen under electron microscope
28
Q

what is magnification

A

how much bigger the image is than the specimen

29
Q

what is resolution

A

-how detailed an image is
-how well a microscope distinguishes between two points that are close together
(increasing magnification won’t help if cannot separate two objects)

30
Q

equation for magnification

A

magnification = image size/actual size

31
Q

explain light microscope

A
  • they use light
  • have a lower resolution than electron microscope (max. resolution of 0.2 micrometres)
  • usually used to look at whole cells or tissues
  • maximum useful magnification is x1500
32
Q

laser scanning confocal microscope

A
  • use laser beams (intense beams of light) to scan a specimen, which is usually tagged with a fluorescent dye
  • laser causes the dye to fluoresce (give off light)
  • light is then focussed through a pinhole onto a detector
  • detector is hooked up to computer, which generates an image. (image can be 3D)
  • pinhole means that any out of focus light is blocked, so produce much clearer image than normal microscope
  • can be used to look at objects at different depths in thick specimens
33
Q

electron microscope

A

-use electrons instead of light to form an image
-have higher resolution so give more detailed image

34
Q

what are the two types of electron microscopes -.IJN

A
  • Transmission electron microscope (TEM)
  • Scanning electron microscope (SEM)
35
Q

explain TEM

A
  • use electromagnets to focus a beam of electrons, which is then transmitted through the microscope
  • denser = absorb more electrons = darker on image you end up with
    :) provide high resolution images so can be used to look at a range of organelles
    :( only used on thin specimens
36
Q

explain SEM

A
  • scan a beam of electrons across the specimen
  • this knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image
    :) show the surface of the specimen and can be 3D
    :( give lower resolution images than TEM
37
Q

give max resolution and magnification of the types of microscopes

A

light= 0.2 micrometres, x1500
TEM= 0.0002 micrometres, >1,000,000
SEM= 0.002 micrometres, <500,000

38
Q

how do light microscopes and TEM produce and image, and why is this significant for staining

A
  • beam of light (electrons) passes through the object being viewed, and some parts of the object absorb more light (electrons) than others
    -if object is transparent, whole image appears white because the light rays just pass straight through
39
Q

staining in light microscopes

A
  • dye is used (like methylene blue and eosin)
    -stain is taken up by some parts of the object than others, leads to contrast which makes the different parts show up
  • different stains are used for different things (Methylene Blue= DNA, Oesin= cell cytoplasms)
  • more than one stain can be used at once
40
Q

staining for electron microscopes

A
  • objects are dipped in a solution of heavy metals, like lead
  • metal ions scatter the electrons, creating contrast (some parts show up darker than others)
41
Q

what is a slide

A
  • strip of clear glass or plastic
  • usually flat
  • some have small dip or well into centre, useful for big or liquid specimens
42
Q

how do you prepare a dry mount

A
  • need to let light through, so for thick specimen, use a thin slice to use
  • use tweezers to pick up specimen
  • put in middle of clean slide
    -put a cover slip on top (square of thin, transparent plastic or glass)
43
Q

prepare wet mount

A
  • pipette a small drop of water onto slide
  • use tweezers to place specimen on top
  • put on cover slip: stand it upright next to water, slowly tilt and lower to cover specimen
  • try not to get any air bubbles in, obstruct view
  • add stain: put droplet next to one edge of cover slip, put paper towel next to opposite edge
  • stain will get drawn up, across the specimen
44
Q

what is a squash slide

A
  • wet mount is prepared first
  • lens tissue is used to gently press down on the cover
45
Q

how do you use light microscope to view specimen

A

1) Start by clipping the slide containing the specimen you want to look at onto the stage.
2) Select the lowest-powered objective lens (i.e. the one that produces the lowest magnification).
3) Use the coarse adjustment knob to bring the stage up to just below the objective lens.
4) Look down the eyepiece (which contains the ocular lens).
Use the coarse adjustment knob to move the stage downwards, away from the objective lens until the image is roughly in focus.
5) Adjust the focus with the fine adjustment knob, until you get a clear image of what’s on the slide.
6) If you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus.

46
Q

what is differential staining

A

staining where more than one dye is used, and each stain binds to a specific cell structure, so the structures can be identified easily and stained differently

  • gram stain technique and acid-fast technique
47
Q

what are features that need to be taken into consideration when making scientific drawing

A
  • include title
  • state magnification
  • use sharp pencil for drawings and labels
  • use at least 1/2 of space available
  • draw smooth, continuous lines
  • do not shade
  • ensure correct proportions
  • no arrow heads on lines and no crossing
  • draw lines with ruler and horizontally
48
Q

what is the difference between an eyepiece graticule and stage micrometer

A

EG: is fitted onto eyepiece, and is like a transparent ruler with numbers, but no units
SM: a slide placed onto the stage, with an accurate scale with units, used to work out the value of the divisions on the eyepiece graticule at that particular division

49
Q

how do you calibrate an eyepiece graticule

A

1) line up the graticule and micrometer
2) not what each division of the micrometer is worth (e.g. 0.1 mm)
3) work out how many divisions of the graticule is one on the micrometer
4) do some fancy maths and work out

Biology Module 2 (6 decks)

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