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Biology > B1.1 Cell Structures > Flashcards

B1.1 Cell Structures Flashcards

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1
Q

State the difference between eukaryotic and prokaryotic cells

A

Eukaryotic:

  • genetic material in nucleus
  • complex + relatively large (10um - 100um)
  • plant + animal cells

Prokaryotic:

  • do not contain nucleus
  • genetic material floats in cytoplasm
  • simple + typically smaller (1um - 10um)
  • bacterial cells
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2
Q

Explain the function of the nucleus

A
  • controls activities of cell
    Contains genetic material, arranged as chromosomes, which determines cell’s appearance + function
  • also contains instructions to make new cells or new organisms
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3
Q

Explain the function of the cell membrane

A
  • selective barrier that controls which substances pass into and out of cell
  • also contains receptor molecules
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4
Q

Explain the function of the mitochondrion

A

Plural - mitochondria

  • site of respiration
  • enzymes enable glucose + oxygen to react together
  • the reactions transfer vital energy to organism
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5
Q

Explain the function of the cytoplasm

A
  • ‘jellylike’ substances

- chemical reactions that keep cell alive take place here

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6
Q

State the subcellular structures in an animal cell

A
  • nucleus
  • cytoplasm
  • mitochondria
  • cell membrane
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7
Q

State the subcellular structures in a plant cell and explain why some of the extra ones are needed

A
  • cell wall
  • vacuole
  • chloroplast

Plants make their own food and cannot move their whole body from place to place so they need these extra subcellular structures.

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8
Q

Explain the function of chloroplasts

A
  • contain green chlorophyll
  • chlorophyll transfers energy from Sun to plant as light, which is used in photosynthesis
  • only found in green parts of plant
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9
Q

Explain the function of the cell wall

A
  • surrounds cell

- made of tough fibre (cellulose) which makes wall rigid to support cell

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10
Q

Explain the function of the vacuole

A
  • full of cell sap, a watery solution of sugar + salts

- it helps keep cell rigid, so supports plant + keeps it upright

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11
Q

What are the seven life processes?

A
  • Movement
  • Reproduction
  • Sensitivity
  • Growth
  • Respiration
  • Excretion
  • Nutrition
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12
Q

Define bacteria and state examples of them

A
  • smallest living organisms
  • unicellular
  • every cell can carry out 7 life processes

Examples:

  • Escherichia coli (E.coli) - causes food poisoning
  • Streptococcus bacteria - causes sore throats
  • Streptomyces bacteria - found in soil. Antibiotic streptomycin comes from this and kills many disease-causing bacteria
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13
Q

State and explain the function of subcellular structures in prokaryotic cells

A
  • cell wall - made of peptidoglycan which holds cell together + protects it
  • genetic material - floats freely in cytoplasm. Bacterial chromosome - normally circular, a long strand of DNA
  • cell membrane
  • cytoplasm
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14
Q

State and explain the function of extra subcellular structures in prokaryotic cells

A
  • Flagella - ‘tail-like’ structures that allow the cell to move through liquids
  • Pili - tiny ‘hairlike’ structures that enable the cell to attach to structures such as cells that line your digestive tract. Also used to transfer genetic material between bacteria
  • Slime capsule - layer outside cell wall which protects a bacterium from drying out and from poisonous substances. Also helps bacteria to stick to smooth surfaces
  • Plasmid - circular piece of DNA that is used to store extra genes. These genes aren’t normally needed for bacterium’s daily survival, but may help in times of stress (where antibiotic resistance genes are normally found)
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15
Q

Describe how light microscopes can be used to view cells

A

Microscope passes light through an object placed on slide on stage, then through 2 glass lenses which magnify the object do when you view it through the eyepiece you can see it in more detail

1- Move stage to its lowest position
2- Select objective lens with lowest magnification
3- Place slide, which has cells on it, on the stage
4- Turn course focus knob slowly until you see your object (it will normally be blurred)
5- Turn fine focus knob slowly until your object comes into clear focus
6- To see cells in greater detail, repeat steps above using a high magnification objective lens

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16
Q

Describe how staining can be used to view cells

A
  • many cells are colourless and so they are stained to make them easier to observe

Common stains:

  • Methylene blue - nucleus of animal cell
  • iodine solution - plant cell nuclei
  • crystal violet - bacterial cell walls
How to apply a stain:
1- Place cells on glass slide
2- Add 1 drop of stain
3- Place coverslip on top
4- Tap coverslip gently with pencil to remove air bubbles
17
Q

Total magnification =

A

Eyepiece lens magnification * objective lens magnification

18
Q

Define resolution

A

Smallest distance between 2 points that can be seen as separate entities

19
Q

Describe how TEMs and SEMs work

A

TEM

  • produce most magnified images
  • work similar to light microscope
  • a beam of electrons (high-energy) passes through a very thin slice of sample
  • beam focused to produce an image

SEM

  • produces 3D image of a surface
  • sends beam of electrons across the surface of a specimen
  • reflected electrons are collected to produce an image
20
Q

Compare light microscopes to Electron microscopes

A 
Light microscope
- cheap to buy + operate 
- small + portable
- simple to prepare sample
- natural colour of sample is seen unless staining is used
- specimens can be dead or living 
Resolution up to 0.2um (2x10^-7m)
Electron microscopes 
- Expensive to buy + operate
- Large + difficult to move
Sample prep is complex
- black & white images produced; false colour can be added to image 
- specimens are dead
Resolution up to 0.1nm (1x10^-10m)
21
Q

Explain how electron microscopy has increased our understanding of sub-cellular structures

A
  • allows scientists to view objects in greater detail and see detail within subcellular structures as of the higher resolution

Biology (16 decks)

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