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Biology > Cell Structure > Flashcards

Cell Structure Flashcards

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1
Q

Define magnification

A

How much bigger an image appears compared with the original object

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2
Q

Define resolution

A

The ability to see two objects as separate and to see tthings fine detail clearly

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3
Q

Why are optical microscopes advanatgeous?

A
  1. relatively cheap
  2. easy to use
  3. portable can be taken into the field
  4. able to study whole living specimens
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4
Q

What can optical microscopes see?

A

Mag 1500X 2000X
wavelength of visible light 400-700nm (200nm)
Ribosomes can’t be seen as 20nm

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5
Q

How do you calculate total magnification?

A

total mag = magnifying power of objective lens x magnifying power of the eyepiece lens

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6
Q

Explain what laser scanning microscopes are and what they’re used for

A
  • use laser light to scan object display on computer
  • high res
  • depth selctivity, focus on strucures at different depths
  • observe whole organims and cells
  • medical uses, biological research, diagnose quickly
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7
Q

Explain the types of electron microscopes are there

A

E-microscopes: wavelength of 0.004nm
TEM transmission
- beam of electrons passed through dehydrated and stained specimen
- produces a 2D black and white electron micrograph
- 2 million X or 50 million X
SEM scanning
- electrons bounce off specimen and focus onto a screen
- 3D image X200,000 black and white but computer used to colour the image

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8
Q

Describe how to use a microscope

A
  1. specimen on a slide placed on the stage and clipped in
  2. rotating nose piece the lowest power lens in placed over specimen
  3. adjust coarse focus knob while looking into the eyepiece until image is clear and in focus
  4. adjust iris diaphragm for optimum light
  5. make sure directly over the whole in stage,roate nose piece and bring X10 objective into place over specimen, use fine focus knob to focus the image
  6. do step 5 with X40 objective lens
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9
Q

What are the disadvantages of an electron microscope?

A
  • large so not portable
  • very expensive
  • need alot of training and skill
  • specimens must be dead
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10
Q

Explain why stains are used and what stains could be used

A

A stain makes the specimen easy to see. Differential staining = some stains bind to specific cell structures, staining each structure differently so the strutures can be easily identified

  1. acetic orcein: binds to DNA, stains chromosomes dark red
  2. methylene blue: all purpose stain
  3. eosin: stains cytoplasm
  4. sudan red: lipids
  5. iodine in potassium iodide solution: cellulose yellow, starch granules blue/black
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11
Q

How to calculate magnification

A

M = I/A

  • measure widest part of leaf in mm
  • convery to um by X1000
  • divide by mag shows actual measurement
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12
Q

Describe how you would observe a prepared specimen

A
  • dehydrate specimen
  • embed in wax to prevent distortion duting slicing
  • special instrument make very thin slices called sections
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13
Q

Why do some mitochondria look like spheres?

A

Cells are 3D and an image of a cell is 2D so depending on how the mitochondria was cut they could appear as different shapes, (longitudinal section)

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14
Q

Draw a table for the epu at different magnifications for most modern microscopes

A

Mag of eyepiece Mag of objective Total mag Epu
x10 x4 x40 25
x10 x10 x100 10
x10 x40 x400 2.5
x10 x100 x1000 1.0
Divide 1000 by total mag = epu

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15
Q

Describe the structure of the nucleus, nuclear envelope and nucleolus

A
  • nuclear envelope surrounds nucleus, there are pores
  • nucleolus contains RNA, no membrane
  • chromatin inside genetic material, wound around histone proteins
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16
Q

Describe the function of the nucleus, nuclear envelope and nucleolus

A
  • nucleus envelope separates the contents of the nucleus from the rest of the cell, some parts fused, ribosomes and substances can pass through
  • pores enable larger substances (mRNA) to leave + steroid hormones
  • nucleolus where ribosomes are made
  • chromosomes contain genes
  • stores genes
  • transmits genetic information
  • instructions for protein synthesis
17
Q

Describe the structure and function of the RER

A
  1. Cisternae are continuous with nuclear membrane and coated with ribosomes
  2. intracellular transport, cisternae are channels
  3. provides large SA for ribosomes, the proteins pass actively through membrane into cisternae, transported to golgi for modification and packaging
18
Q

Describe the structure and function of the SER

A
  1. cisternae continuous with nuclear membrane and no ribosomes
  2. contains enzymes catalyse synthesis:
    - cholesterol
    - lipids/phospo
    - steroid hormones
  3. absorption, syntheisis, transport of lipids
19
Q

Describe the structure and function of the golgi apparatus

A
  1. stack of membrane bound flatterned sacs
  2. proteins mod:
    - glycoproteins (sugar adding)
    - lipoproteins (lipid)
    - folded into 3D
  3. proteins packaged into vesicles that are pinched off
    - stored in the cell
    - moved to plasma membrane (exported or become part of the membrane)
20
Q

Describe the structure and function of the mitochondria

A
  1. 2-5um, 2 membranes, outer and inner, fluid filled between, inner is highly folded into cisternae, inner part is fluid filled matrix
  2. site of ATP production during aerobic respiration
  3. abundant in cells where much metabolic activity happens (liver, neurones)
  4. self replicating can be made if energy needs increase
21
Q

Describe the structure of chloroplasts

A
  1. 4-10um plant cells, some protists, surrounded by double membrane, inner membrane is continuous with stacks of flattened membrane sacs celled thylakoids
  2. thylakoids contain chlorophyll. each stack is called a granum
  3. fluid filled matrix = stroma, contains loop of DNA and starch grains
22
Q

Describe the function of chloroplasts

A
  1. site of photosyntheis = in grana light energy is trapped, H2O is split to supply H+
  2. in stroma = Hydrogen produces CO2 using energy from ATP to make carbohydrates
23
Q

Describe the structure and function of the vacuole

A
  1. surrounded by tonoplast
  2. Plant cells only have large permanent vacuole
    Filled with water/solutes and maintains cell stability, making cell turgid = helps support plants
24
Q

Describe the structure and function of lysosomes

A
  1. small bags formed from the golgi apparatus, contain hydrolytic enzymes, abundant in phagocytes
  2. keep the powerful enzymes separate from the cell + engulf old organells and foreign matter, digest and reuse components
25
Q

Describe the structure and function of cilia and undulipodia

A
  1. protrusions from the cell and surrounded by cell surface membrane, each contain microtubules and formed from centrioles
  2. epithelium cells in airway, mucus, most cells have one to act to detect signas about its environment
  3. sperm has undulipodim enables sperm movement
26
Q

Describe structure and function of the ribosomes

A
  1. made of ribosomal RNA, made in nucleolus as 2 separate subunits then pass through envelope and combine in cytoplasm
  2. RER mainly for synthesising proteins that will be exported
  3. free ribosomes are site of proteins that will be used in the cell
27
Q

Describe the structure and function of the centrioles

A
  1. 2 bundles of microtubules at right angles to each other, made of tubulin subunits and arranged to form a cylinder
  2. Spindle forms from the centriole
  3. Centrioles multiply and line up beneath the cell surface membrane, microtubules sprout up from each centriole forms cilia etc
28
Q

Describe the structure of the cytoskeleton

A
  1. rod like microfilaments made of subunits of the protein actin 7nm
  2. intermediate filaments 10nm
  3. microtubles straight, cylindrical tubulin 18-30nm
  4. Motor proteins myosins, kinesins, dyneins also enzymes allows hydrolysis of ATP
29
Q

Describe the function of the cytoskeleton

A
  1. Microfilaments = support and mechanical strength, give shape and allow movement
  2. Intermediate filaments = anchor nucleus within cytoplasm, extend between cells enabling cell signalling and allowing cells to adhere to a basement membrane, stabalise tissue
  3. Microtubules = shape and support, help substances to move through the cell
    - form track motor proteins walk across
    - form spindle before cell divides
    - make up cilia, centrioles, undulipodia
30
Q

Describe the structure and function of the cellulose cell wall

A
  1. Cell wall made of cellulose:
    - prevent cells from bursting when turgid
    - provide strength and support
    - maintain cell shape
    - contribute to strength and support of whole plant
    - permeable and allow solutions to pass through
31
Q

Explain the process of making and secreting a protein

A
  1. Instructions in the nucleus are transcribed onto length of mRNA. Many copies are made
  2. mRNA leaves the nucleus through a nuclear pore
  3. Attach to ribosomes (RER) the instructions are translated and insulin molecules are assembled
  4. the molecules pass into cisternae of the RER and along the hollow sacs, vesicles are pinched off from RER and pass via microtubles and motor proteins to Golgi
  5. Vesicles fuse with golgi where molecule is modified for release and packaged
  6. inside vesicles pinched off from golgi and pass to the plasma membrane
  7. Vesicles and plasma membrane fuse and molecules is released to outside
32
Q

List the similarities between prokaryotes and eukaryotes

A
  • plasma membrane
  • cytoplasm
  • ribosomes
  • DNA and RNA
33
Q

List the differences between prokaryotes and eukaryotes

A
  • smaller
  • less well developed cytoplasm no centrioles
  • no nucleus
  • no mitochondria, RER, chloroplasts or golgi
  • peptidoglgan not cellulose
  • smaller ribosomes
  • naked DNA floats free
  • protective waxy capsule
  • plasmids
  • flagella to move
  • pili adhere to host cells
34
Q

How do bacteria divide?

A

Binary fission. Don’t have linear chromosomes so don’t carry out mitosis. DNA is copied before so each new cell recieves large loop DNA and plasmids

35
Q

What evidence is there to support endosymbiont theory?

A

Mitochondria and chloroplasts and bacteria:

  • small ribosomes (70s)
  • loops of DNA
  • RNA
  • divide by binary fission
36
Q

Outline a method that could be used to determine the density of hairs on the underside of a leaf

A

A section of the leaf should be put under the microscope, count the individual hairs in that section then divide by that area to calculate a hair density per unit area

Biology (12 decks)

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