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Biology > Unit 2 - Cell Structure > Flashcards

Unit 2 - Cell Structure Flashcards

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1
Q

What is a tissue?

A

A group of cells working together to perform a particular function.

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2
Q

What is an organ?

A

It is a group of tissues which work together to carry out a particular function.

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3
Q

What is an organ system?

A

It is a group of organs which work together to carry out a particular function.

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4
Q

What are prokaryotes?

A

Single celled organisms such as bacteria.

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5
Q

Definition of a eukaryotic cell?

A

Eukaryotic means the cell contains a membrane bound nucleus/membrane bound organisms.

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6
Q

Examples of eukaryotes?

A

Plant cells, animal cells, algae cells and fungi cells.

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7
Q

What are viruses classed as?

A

They’re not eukaryotic or prokaryotic, they’re acellular and non-living.

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8
Q

What do animal cells contain?

A

Cell surface (plasma) membrane
Rough endoplasmic reticulum
Nucleus (nucleolus and nuclear envelope)
Smooth endoplasmic reticulum
Lysosome
Ribosome
Golgi apparatus
Cytoplasm
Mitochondria

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9
Q

Diagram of an animal cell?

A
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10
Q

What do plant cells contain?

A

Cell surface membrane
Chloroplast
Rough endoplasmic reticulum
Mitochondria
Plasmodesmata
Golgi apparatus
Vacuole
Smooth endoplasmic reticulum
Cytoplasm
Nucleus (nucleolus/ nuclear envelope)
Ribosome
Cell wall (cellulose)

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11
Q

Diagram of a plant cell?

A
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12
Q

How does a plant cell differ from an animal cell?

A

Plant cells contain a cellulose cell wall, a vacuole and chloroplasts, whereas animal cells don’t.

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13
Q

What does algal cells contain?

A

Ribosomes
Cellulose cell wall
Vacuole
Cell-surface membrane
Mitochondria
Smooth endoplasmic reticulum
Rough endoplasmic reticulum
Golgi apparatus
Cytoplasm
Nucleus (nucleolus/nuclear envelope)
1, long chloroplast

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14
Q

How do algal cells differ from plant cells?

A

They can be unicellular or multicellular and the chloroplasts are often a different size and shape (i.e. 1, long one).

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15
Q

Diagram of an algal cell?

A
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16
Q

What do fungal cells contain?

A

Ribosomes
Cell surface membrane
Rough endoplasmic reticulum
Nucleus (nucleolus/nuclear envelope)
Mitochondria
Golgi apparatus
Smooth endoplasmic reticulum
Cytoplasm
Chitin cell wall
Vacuole

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17
Q

How do fungal cells differ from plant cells?

A

Their cell walls are made of chitin not cellulose and they don’t have chloroplasts (because they don’t photosynthesise).

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18
Q

Diagram of a fungal cell?

A
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19
Q

Structure and function of the nucleus?

A

The nucleus contains the genetic material in the form of chromatin which is made of DNA coiled around histone proteins. When this chromatin is condensed it forms chromosomes which contain many genes. It has a double membrane with nuclear pores, which allows the passage of molecules in and out of the nucleus. The nucleolus makes ribosomes.

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20
Q

Structure and function of a mitochondrion?

A

They carry out aerobic respiration producing ATP. They have a double membrane. The inner membrane is folded to form cristae which increases the surface area for the attachment of enzymes and proteins involved in aerobic respiration. The matrix contains enzymes involved in aerobic respiration. Mitochondria have their own DNA and ribosomes that are used to make enzymes for aerobic respiration.

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21
Q

Structure and function of a chloroplast?

A

They’re the site of photosynthesis. They have a double membrane and also have membranes inside called thylakoids which contain the chlorophyll for photosynthesis. The thylakoids are stacked up to form grana which increases surface area for absorption of light. Stroma is a fluid which contains the enzymes for photosynthesis. They contain their own DNA and ribosomes to make enzymes for photosynthesis. They contain starch grains, storing the products of photosynthesis (glucose) as starch.

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22
Q

Structure and function of ribosomes?

A

They carry out protein synthesis. They are made from ribosomal RNA (rRNA) and protein. Each ribosome is made up of 2 sub units. They are found in the cytoplasm or attached to the rough endoplasmic reticulum. Eukaryotic cells contain larger 80s ribosomes. Prokaryotic cells contain smaller 70s ribosomes.

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23
Q

Structure of the endoplasmic reticulum?

A

It is made of membranes and forms a series of enclosed flattened sacs called cisternae. There are 2 types:
-rough endoplasmic reticulum
-smooth endoplasmic reticulum

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24
Q

Structure and function of the rough endoplasmic reticulum?

A

It has ribosomes on its outer surface which give it the ‘rough’ appearance. These ribosomes synthesise proteins which are then transported through the cell by the rough endoplasmic reticulum.

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25
Q

Structure and function of the smooth endoplasmic reticulum?

A

It synthesises and transports lipids. It does not have ribosomes on its outer surface.

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26
Q

Diagram of the nucleus?

A
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27
Q

Diagram of mitochondria?

A
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28
Q

Diagram of chloroplast?

A
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29
Q

Diagram of ribosomes?

A
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30
Q

Diagram of rough and smooth endoplasmic reticulum?

A
31
Q

Structure and function of the Golgi apparatus?

A

It processes, modifies and packages proteins into vesicles, for transportation out of the cell (secretion). The membrane sacs are fluid filled and bud off smaller sacs called vesicles at their ends which contain the proteins that have been modified. They can form lysosomes.

32
Q

Diagram of the Golgi apparatus?

A
33
Q

Structure and function of lysosomes?

A

Lysosomes are vesicles containing enzymes called lysozymes which cause hydrolysis. Some types of white blood cells contain many lysosomes, as they hydrolyse foreign pathogens.

34
Q

Diagram of lysosomes?

A
35
Q

Structure and function of cell-surface membrane?

A

It is also referred to as the ‘plasma’ membrane. It controls the passage of molecules in and out of cell. It is made up of phospholipids, proteins, and carbohydrates arranged into a fluid mosaic model.

36
Q

Structure of a cell-surface membrane?

A
37
Q

Structure and function of microvilli?

A

Microvilli are formed from the folding of the cell-surface membrane, which greatly increases surface area. Only certain types of cells have microvilli such as epithelial cells that line the small intestine.

38
Q

Diagram of microvilli?

A
39
Q

Structure and function of centrioles?

A

The centrioles form spindle fibres used in cell division.

40
Q

Structure and function of the vacuole?

A

It’s found in plant cells only. It contains cell sap - a solution of sugar and salts. The surrounding membrane is called the tonoplast. The vacuole helps to maintain the pressure inside the cell keeping the cell turgid. This stops the plant from wilting. It’s also involved in the isolation of unwanted chemicals inside the cell.

41
Q

Diagram of a vacuole?

A
42
Q

How are epithelial cells of the small intestine adapted for absorption?

A

They contain microvilli to increase surface area for absorption. They have many mitochondria to provide ATP for the active transport of substances across the membrane.

43
Q

How are red blood cells specialised?

A

They have no nucleus so that there is more room for haemoglobin. This means that more oxygen can be carried per cell.

44
Q

How are sperm cells adapted?

A

These cells contain a lot of mitochondria to produce large amounts of ATP needed to propel them towards the egg.

45
Q

What does a bacteria cell contain?

A

Cytoplasm
Cell-surface membrane
Murein cell wall
Slime capsule
Plasmids
Floating DNA
Flagellum

46
Q

Diagram of a bacteria cell?

A
47
Q

What is the flagellum?

A

A long hair-like structure that rotates to make the prokaryotic cell move. Not all prokaryotes have a flagellum.

48
Q

What are plasmids?

A

Small loops of DNA that aren’t a part of the main circular DNA molecule. They can be transferred between plasmids.

49
Q

What is the function of a slime capsule?

A

It helps to protect the bacteria from attack by cells of the immune system.

50
Q

How do prokaryotes and eukaryotes differ?

A

Prokaryotes DNA is circular and not associated with histone proteins, but eukaryotes DNA is linear and associated with histone proteins. Prokaryotes contain no membrane bound organelles, but eukaryotes contain membrane bound organelles. Prokaryotes have no nucleus, DNA is free in cytoplasm, but eukaryotes have a nucleus, DNA is contained within a nuclear membrane. Prokaryotes contain smaller ribosomes (70s), but eukaryotes contain larger ribosomes (80s). Some prokaryotes may have capsule, one or more flagella, one or more plasmids, but eukaryotes do not have a capsule, flagella and plasmids. Prokaryotes have a cell wall made of murein, a glycoprotein, but eukaryotes either have:
-no cell wall
-cellulose cell wall
-chitin cell wall

51
Q

Why are viruses acellular and non-living?

A

They have no cell-surface membrane, not metabolism and cannot independently move, respire reproduce or grow.

52
Q

Diagram of a virus particle?

A
53
Q

Use of attachment proteins?

A

They’re used to attract host cells, so the virus can enter the cell and use the cell to replicate.

54
Q

Principles of a light microscope?

A

Specimens are illuminated with light, which is focused using glass lenses and viewed using the eye. Specimens can be living or dead, but often need to be stained with a coloured dye to make certain organelles visible.

55
Q

Limitations of a light microscope?

A

The resolution of the light microscope is lower, so only large organelles such as the nucleus can be observed; smaller organelles such as the Golgi apparatus cannot be seen. The resolution of the light microscope is limited by the wavelengths of the light.

56
Q

Definition of resolution?

A

The ability to distinguish between 2 objects that are close together, as separate objects.

57
Q

Definition of magnification?

A

How much larger the object appears than its real size.

58
Q

Principles of an electron microscope?

A

It uses a beam of electrons, rather than light, to image the specimen. A beam of electrons has very small wavelength, so can be used to observe small organelles such as endoplasmic reticulum and ribosomes. They have a much higher resolution and magnification than optical microscopes.

59
Q

Limitations of electron microscopes?

A

Specimens must be viewed in a vacuum, and must therefore be dead-living specimens cannot be viewed.
The specimens require a more complex staining process with an electron-dense chemical.
The specimen must be very thin, which is difficult to do.

60
Q

Transmission electron microscope (TEM)?

A

They work much like a light microscope, transmitting a beam of electrons through a thin specimen and then focusing the electrons to form an image on a screen. This has the highest resolution. A TEM microscope can only produce a 2D image, only in black and white.

61
Q

Scanning electron microscope (SEM)?

A

Scans a fine beam of electrons onto a specimen and collects the electrons scattered by the surface on a screen.
This has lower resolution than a TEM but higher than an optical microscope.
An SEM gives a 3D image of surfaces, only in black and white. The samples do not have to be so thin.

62
Q

What are microscope artefacts?

A

They are things you can see down the microscope that aren’t part of the cell or specimen that you’re looking at. These could be dust, air bubbles or fingerprints, etc. They usually result as part of the preparation process.

63
Q

Equation for magnification?

A

Image size divided by actual size.

64
Q

How many micrometers in 1mm?

A

1mm = 1,000 micrometers

65
Q

How many nanometres in 1 micrometer?

A

1micrometer = 1,000nm

66
Q

How do you calibrate an eyepiece graticule with a stage micrometer?

A

1) Line up the eyepiece graticule and the stage micrometer.
2) Each division on the stage micrometer is 0.1mm long.
3) See how many eyepiece graticule units are in 1 stage division.
4) To work out the size of 1 division on the eyepiece graticule, you need to divide 0.1 by how many how many eyepiece graticule units are in 1 stage division.

67
Q

How can you use an eyepiece graticule and stage micrometer to measure the diameter of an object?

A

1) At a particular magnification, calibrate the eyepiece graticule against a stage micrometer, so that the actual length of 1 eyepiece graticule is known in micrometers.
2) Randomly choose a field of view.
3) Measure the diameter of the object in eyepiece graticule units.
4) Actual diameter of object in um=diameter of object in eyepiece graticule units multiplied by actual length of graticule units.
5) Repeat for a large number of objects and calculate a more representative mean.

68
Q

What is cell fractionation and ultracentrifugation used for?

A

To study the function of an organelle and separate it from the cell.

69
Q

What is the homogenise step of separating organelles from their cell?

A

The tissue is homogenised in an ice-cold, isotonic, buffered solution to break open the cells and release the organelles.

70
Q

Why is an ice-cold, isotonic, buffered solution used?

A

Ice-cold:reduce the action of enzymes that would damage organelles.
Isotonic:prevent the net movement of water into or out of organelles by osmosis, so organelles don’t burst.
Buffered:to stop pH changes which could denature proteins (in the organelles).

71
Q

What is the filter step in separating organelles from their cells?

A

The mixture can then be filtered to remove cell debris and unbroken cells, producing a solution of suspended organelles.

72
Q

What is the ultracentrifugation part of separating organelles from their cells?

A

1) the solution is now centrifuged at low speed. Larger organelles I.e. nuclei are forced to the bottom of the tube into a pellet. This pellet is removed, leaving the supernatant.
2) the supernatant is centrifuged at a higher speed. Smaller organelles are forced to the bottom of the tube into a pellet.
3) this process can then be repeated, increasing the speed of the centrifuge with each speed (differential centrifugation). This separates organelles according to mass.

73
Q

Order of the pellets?

A

-Nuclei
-Chloroplasts (if plant cells)
-Mitochondria
-Ribosomes

Biology (20 decks)

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