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Biology A Level > Cells > Flashcards

Cells Flashcards

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1
Q

What type of cells is the nucleus found in?

A

Plant + animal cells.

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2
Q

What does the nucleus do in the cell?

A

Largest organelle.
Large holes in cover contains proteins - control exit of substances. (E.g. RNA from nucleus).
Controls cell activity (controls transcription/starting point for making proteins with DNA).

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3
Q

What type of cells is the nucleolus found in?

A

Plant+animal cells.

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4
Q

What does the nucleolus is do?

A 
Dark region of chromatin/in the nucleus. 
Makes ribosomes (involved in process of making ribosomes).
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5
Q

What type of cells are ribosomes found in?

A

Plant+ animal cells.

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6
Q

What are the two types of ribosomes?

A 
80s = in eukaryotic cells. 
70s = in prokaryotic cells.
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7
Q

What do ribosomes do?

A

Either free in cell’s cytoplasm - make proteins for cell use/ or found attached to the rough endoplasmic reticulum - make proteins to export from the cell.
Site of protein synthesis.

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8
Q

What is the structure of a ribosome?

A

Have 2 sub-units, one large, one small.
Each contain rRNA and protein.
Small cytoplasmic granules.

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9
Q

What type of cells are Mitochondrion found in?

A

Plant+animal cells.

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10
Q

What do the Mitochondrion do?

A

Aerobic respiration happens here.

Sausage-shaped organelle.

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11
Q

What type of cells are the Golgi apparatus found in?

A

Plant+animal cells.

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12
Q

What does the Golgi apparatus do?

A

Job=to transport proteins from the Rough Endoplasmic Reticulum to the cell membrane for export.
A series of flattened membrane vesicles, formed from the endoplasmic reticulum.

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13
Q

What type of cells are the Golgi Vesicles found in?

A

Plant+animal cells.

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14
Q

What do the Golgi Vesicles do?

A

Job=to transport proteins.

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15
Q

What type of cells are lysosomes found in?

A

Plant+animal cells.

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16
Q

What does the lysosome do?

A

Job=to break down unwanted chemicals, toxins, organelles or even whole cells, so the materials can be recycled.
Also can fuse to digest its contents.

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17
Q

What type of cells is the the rough endoplasmic reticulum found in?

A

Plant+animal cells.

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18
Q

What does the rough endoplasmic reticulum do?

A

Job=Ribosomes (on outside) synthesise (make) proteins, which is processed in the rough endoplasmic reticulum, before being exported from the cell by the Golgi body.
Ribosomes on the outside/surface give it its rough appearance.
Folds inside-increase surface area - more photosynthesis.

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19
Q

What type of cells is the smooth endoplasmic reticulum found in?

A

Plants+animal cells.

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20
Q

What does the smooth endoplasmic reticulum do?

A

Series of membrane channels - help synthesising and transporting materials particularly lipids, which the cell need. Makes+transports steroids and fats.

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21
Q

What type of cells is a chloroplast found in?

A

Plant cells only.

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22
Q

What does the chloroplast do?

A

Where photosynthesis takes place.

Are only found in photosynthetic organisms (plants and algae).

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23
Q

What type of cells is the cell wall found in?

A

Plant cells only.

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24
Q

What does the cell wall do?

A

A thick layer outside the cell membrane - cell strength + rigidity for the cell.
Plant cell walls are mainly made of cellulose.
Animals do not have a cell wall, only plants do.

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25
Q

What features does a cell wall have?

A

Many polysaccharides, e.g. Cellulose.
Thin layer called the lamella - marks boundary between adjacent cell walls + cements adjacent cell walls together.
Microfibrils of cellulose in matrix = considerable strength to strength of whole cell.

26
Q

What are the functions of a cell wall?

A

Mechanical strength - prevent cell wall bursting under pressure from osmotic gain/as a whole.
Allow water to pass along - contribute to movement of water across plant.

27
Q

What are algae cell walls made of?

A

Cellulose/glycoproteins - or both.

28
Q

What are fungi cell walls made of?

A

Chitin.

29
Q

What type of cells is the cell vacuole found in?

A

Plant cells only.

30
Q

What does a cell vacuole do?

A

Membrane-bound sacs containing water/dilute solutions of salts/other solutes.
Plant cell vacuoles are filled with cell sap - very important in keeping the cell rigid/turgid.
Only in plants NOT animals.

31
Q

What is the nuclear envelope?

A

A double membrane that surrounds the nucleus.

Its outer membrane is continuous with the endoplasmic reticulum of the cell and often has ribosomes on its surface.

32
Q

How to light microscopes work?

A

They use convex lenses in order to magnify an image.

33
Q

What is a limitation of light microscopes? And how can this be overcome?

A

They have a relatively long wavelength for their light rays, which means that a light microscope can only distinguish between two objects if they are 0.2 micrometer, or further apart.
Can be overcome, by using electron beams instead of beams of light as electron beams have shorter wavelengths so the beams of electrons in electron microscopes can distinguish between two objects only 0.1 micrometers apart.

34
Q

What is the definition for the magnification of an object?

A

The magnification of an object is how many times bigger the image is compared to the object.

35
Q

What is the formula for magnification?

A

Magnification = size of image divided by the size of the real image.
Important thing to remember when calculating the magnification is to ensure that the units of length are the same for both the object and the image.

36
Q

What is the formula for the size of the real object and what must you always remember to check here?

A

Size of real object = size of image divided by magnification.
Important thing to remember when calculating the magnification is to ensure that the units of length are the same for both the object and the image.

37
Q

What is the symbol for kilometres and what is its equivalence in metres?

A

km.

10^3.

38
Q

What is the symbol for metres and what is its equivalence in metres?

A

m.

1.

39
Q

What is the symbol for millimetres and what is its equivalence in metres?

A

mm.

10^-3.

40
Q

What is the symbol for micrometers and what is its equivalence in metres?

A

u(with a line going down on the left side of the u)m.

10^-6.

41
Q

What is the symbol for nanometers and what is its equivalence in metres?

A

nm.

10^-9.

42
Q

What is the triangle for magnification formulas?

A

Size of image on top.
Size of image on bottom left.
Magnification in bottom right.

43
Q

How do you get from mm to micrometers to nanometers?

A

mm x1000 micrometers x1000 nm.

44
Q

What is the definition for the resolution of a microscope?

A

The minimum distance apart that two objects can be in order for them to appear as separate items.

45
Q

What is another name for the resolution of a microscope?

A

The revolving power of a microscope.

46
Q

For every type of microscope what does the revolving power depend on?

A

For every type of microscope, the revolving power depends on the wavelength of form of radiation used.

47
Q

What is the resolution in a light microscope and what does this mean?

A

In a light microscope the resolution of the microscope is about 0.2 micrometers. This means that any two objects which are 0.2 micrometers or more apart will be seen separately as two separate objects, but any two objects closer than 0.2 micrometers apart will appear a single item.

48
Q

What does greater resolution mean?

A

Greater resolution = greater clarity, so the image produced is clearer and more precise.

49
Q

What does increasing the magnification mean?

A

Increasing the magnification increases size of image, but doesn’t always increase resolution. Every microscope has a limit of resolution. Up to this point increasing magnification will reveal more detail but beyond this point increasing the magnification will not do this. The object while appearing larger, will just be more blurred.

50
Q

What is cell fractionation and what is it used for?

A

Cell fractionation = the process where cells are broken up and the different organelles they contain are separated out.
In order to study the structure and function of the various organelles that make up the cells, it is necessary to obtain large numbers of isolated organelles.

51
Q

Before cell fractionation happens the tissue being tested is placed in a solution. Name the 3 different factors if this solution and explain why they are this.

A

Before cell fractionation tissue is placed in a cold, buffered solution of the same water potential as the tissue. The solution is:
Cold - to reduce enzyme activity that may break down organelles in the cells.
Of the same water potential as tissue - to prevent organelles bursting/shrinking due to osmotic gain/loss of water.
Buffered - so pH does not fluctuate. Any change in pH = changes in structure of the organelles or it can affect the function of enzymes in the body.

52
Q

What are the two stages of cell fractionation?

A

Homogenisation and Ultracentrifugation.

53
Q

What happens in homogenation?

A

Cells are broken up by a homogeniser (blender).
This releases the organelles from the cell.
The resultant fluid, known as the homogenate, is ten filtered to remove any complete cells and large pieces of debris.

54
Q

What happens in ultracentrifugation?

A

This is the process when fragments in filtered homogenation are separated in a machine called a centrifuge. This spins tubes of homogenate at very high speeds in order to create a centrifugal force.

55
Q

What is the homogenation process like for animal cells?

A

For animal cells, the process is as follows:

  • tube of filtrate is placed in the centrifuge and spun at a slow speed.
  • Heaviest organelles, the nuclei are forced to the bottom of the tube where they form a thin sediment or pellet.
  • The fluid at the top of the tube (the supernatant) is then removed, leaving just the sediment of nuclei.
  • The supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before.
  • The next heaviest organelles, the mitochondria, are forced to the bottom of the tube.
  • The process is continued in this way so that, at each increase in speed, the next heaviest organelle is sedimented and separated out.
56
Q

List the order that organelles get separated out of the homogenate in homogenation and the speed of centrifugation/revolutions min^-1 that they are separated out at.

A 
1st = Nuclei at 1,000 revolutions min^-1. 
2nd = Mitochondria at 3,500 revolutions min^-1. 
3rd = Lysosomes at 16,500 revolutions min^-1.
57
Q

What do the techniques of cell fractionation enable?

A

Techniques of cell fractionation and ultracentrifugation enabled great advances in biological knowledge. Allowed a detailed study of the structure and function of organelles, by showing what isolated components do.

58
Q

What a the structure of a vacuole like?

A

Fluid-filled sac bound by a single membrane called a tonoplast.

59
Q

What are the functions of a vacuole?

A

Support herbaceous plants and herbaceous parts of Soddy plants to make cells turgid
Sugars and amino acids as a temporary food store.
Pigments may colour petals to attract pollinating insects.

60
Q

If a cell has lots of mitochondrion what does this mean about the cell’s role?

A

Requires lot of ATP so has a high rate of metabolism.

61
Q

What does it mean about the cell’s role if a cell has a very dense/many cristae in its mitochondrion?

A

More surface area for ATP, so means a greater metabolic rate for these mitochondrion.

62
Q

Which organelles cannot be seen under an optimal microscope?

A

Mitochondrion, endoplasmic reticulum, lysosome, ribosome, cell-surface membrane.

Biology A Level (13 decks)

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