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AQA Biology > 2.1 Cell Structure > Flashcards

2.1 Cell Structure Flashcards

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1
Q

Why do light microscopes use glass lenses to resolve images that are
0.2 um apart

A

0.2 um is the wavelength of light and therefore restricts resolution of light microscopes

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2
Q

What’s the magnification equation

A

Magnification = image/ real

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3
Q

What’s the definition of resolution

A

Minimum distance apart that 2 objects can be distinguished as separate objects in an image

The greater the resolution, the more clear the image will be

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4
Q

How far can an electron microscope distinguish separate objects apart

A

0.1 nm

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5
Q

2 main types of Electron Microscopes

A

TEM and SEM

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6
Q

What do electron microscopes use instead of the wavelength of light

A

A beam of electrons that are focused by electromagnets inside a vacuum environment

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7
Q

Why is a vacuum environment needed

A

So that air particles don’t deflect electrons out of beam alignment

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8
Q

How does TEM work

A

Beam of electrons passes through thin section of specimen.

Areas that absorb the electrons appear darker on micrograph that’s produced

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9
Q

How does SEM work

A

Beam of electrons pass across surface and scatter

Pattern of scattering builds up a 3D image depending on contours of specimen

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10
Q

Limitations of TEM and SEM

A
  • whole system must be in a vacuum so living organisms cannot be observed
  • complex staining process which may introduce artefacts in final images
  • specimens have to be thin so electrons can pass through
  • SEM has resolving power less than TEM but higher than Light
  • both are crazy expensive AF
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11
Q

Define cell fractionation

A

Where different parts and organelles of cells are separated so that they can be studied in detail

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12
Q

What’s the method of cell fractionation

A

Centrifugation

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13
Q

Describe process of homogenisation

A
  1. Cells are blended in homogeniser to create fluid homogenate
  2. Heaviest organelles are forced into bottom of tube forming a pellet (nuclei)
  3. Fluid on top of pellet is called supernatant and must be removed leaving sediment of pellet
  4. Supernatant is transferred to another tube and this time a new heavy pellet is formed (mitochondria)
  5. Process continues with increasing speeds to produce next heaviest organelles that are sedimented and supernatant is separated
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14
Q

Why is the homogenate placed in a cold, buffered solution of the same water potential as cells

A

Prevent organelles from bursting under osmotic pressure

To prevent enzymes from breaking down organelles

So pH doesn’t fluctuate

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15
Q

What’s the Nucleus

A

Double membrane called nuclear envelope containing ~3000 pores to enable molecules entering and leaving

Contains chromatin and nucleolus which is site of ribosome production

Granular jelly (nucleoplasm) makes up the bulk of it

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16
Q

What’s RER

A

Series of flattened sacs that are enclosed by a membrane with ribosomes on surface

Folds and processes proteins made on ribosomes

17
Q

What’s SER

A

System of membrane bound sacs

Produces and processes lipids

18
Q

What’s Golgi apparatus

A

Series of fluid filled flattened and curved sacs with vesicles surrounding its edges

Processes and packages proteins and lipids

Also produces lysosomes

19
Q

What’s Mitochondria

A

Site of aerobic respiration to produce ATP

Oval shaped, bound by double membrane (envelope)

Inner membrane is folded to form Cristae with Matrix on inside containing enzymes needed for respiration

20
Q

What’s Cristae

A

Site of electron transport chains

21
Q

What’s Matrix

A

Contains mitochondrial DNA, respiratory enzymes, lipids and proteins

22
Q

What’s chloroplasts

A

Site of photosynthesis to convert solar energy into chemical energy

A vesicular plastid with double membrane

  • Thylakoids are flattened discs stacked to form grana; contains photosystems with chlorophyll
  • Integranal lamellae are tubes attached to thylakoids in adjacent grana
  • Stroma is a fluid filled matrix
23
Q

What’s Lysosomes

A

Sac surrounded by single membrane embedded H+ pump maintains acidic conditions containing hydrolase enzymes

Glycoproteins coat protects cell interior

Digest contents of phagosome

Exocytosis of digestive enzymes

24
Q

What’s ribosomes

A

Formed of proteins and rRNA free in cytoplasm or attached to ER

Site of protein synthesis via translation:
- Large subunit: joins amino acids
- Small subunit: contains mRNA binding site

25
Q

What’s cisternae

A

Network of tubules and flattened sacs extends from cell membrane through cytoplasm and connects to nuclear envelope

Also linked to RER and SER

26
Q

What’s cell wall

A

In bacteria it’s made up of polysaccharide murein

In plants it’s made up of cellulose microfibrils which allow molecules to pass through in between cells

Middle lamella acts as a boundary between adjacent cell walls

Keeps cell rigid, acts as a physical barrier against pathogens, part of apoplast pathway (plants) to enable easy diffusion of water

27
Q

What’s cell vacuole

A

Surrounded by single membrane (tonoplast), contains cell sap (mineral ions, water, enzymes, soluble pigments)

Controls turgor pressure

Absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm

28
Q

Explain some common cell adaptations

A

Microvilli increases SA e.g. diffusion

Lots of Mitochondria is suitable for large amounts of ATP to be released for active transport

Walls one cell thick to reduce distance of diffusion pathway

29
Q

What’s plasmids

A

Circular piece of DNA carrying non- essential genes

30
Q

What’s capsule

A

Protective slimy layer which helps cell to retain moisture and adhere to surfaces

31
Q

What’s flagellum

A

A tail like structure which rotates to move the cell

32
Q

What’s pili

A

Hair like structure which attaches to other bacterial cells

33
Q

What’s mesosomes

A

Artefacts when cells are prepared for electron microscopy

34
Q

What are viruses

A

Non living structures which consist of nucleic acid enclosed in a protective protein coat called capsid sometimes covered with a lipid layer (envelope)

35
Q

What’s the organisation for multicellular organisms

A

Cells
|
Tissues
|
Organs
|
Organ Systems

AQA Biology (11 decks)

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