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BIOLOGY OCR A > 2.1 Cell structure > Flashcards

2.1 Cell structure Flashcards

1
Q

What is a microscope?

A

Instrument that allows an object to be magnified

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2
Q

When was the first light microscope developed?

A

16th to 17th century

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3
Q

When was the first cell observed, by who?

A

1665, Robert Hooke

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4
Q

When was the first living cell observed?

A

1674

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5
Q

When was the first nucleus observed, by who?

A

1833, Robert Brown

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6
Q

When was the universal cell theory made, what is it?

A

1873, “all living things are composed of cells and cell products”

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7
Q

How does a light microscope work?

A

Two lenses, objective and eyepiece. Light passes through the specimen

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8
Q

What is magnification?

A

How much bigger the image is than the actual object

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9
Q

What is resolution?

A

The ability to distinguish between two objects

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10
Q

What is magnification and resolution of a light microscope?

A

Magnification up to 2000
Resolution of 200nm

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11
Q

What is the equation for magnification?

A

M = Image size / Actual size

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12
Q

What is the difference between dry and wet mounts, examples?

A

Dry mount - thin small samples are placed on the slide with a coverslip on top. Eg hair/pollen
Wet mount - Specimens are suspended in liquid, coverslip is placed at an angle. Eg aquatic samples

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13
Q

What is a squash slide, example?

A

Wet mount, a soft sample is squashed between two slides, creating a thin layer of cells. Eg Root tips

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14
Q

What is a smear slide, example?

A

A wet mount, the edge of a different slide is used to smear a sample, creating a thin, even layer of cells. Eg blood

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15
Q

Why is it important to stain light microscope samples?

A

Increase contrast between organelles, by being absorbed more or less by different components

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16
Q

How to stain a slide?

A

Sample is allowed to air dry, then passed through a flame, the specimen is now adhered to the slide, and will take up the stain

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17
Q

What are crystal violet and methylene blue attracted to?

A

Negatively charged materials in cytoplasm

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18
Q

What are Congo red and Nigrosin attracted to?

A

Repelled by negatively charged cytosol, so dye stains outside of cells

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19
Q

What does differential staining do?

A

Distinguishes between two types of organisms that would otherwise be harder to identify

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20
Q

What is the risks of staining?

A

Many stains are an irritant

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21
Q

How should scientific drawing be drawn?

A

Title, magnification, sharp pencil, white unlined paper, big drawing, smooth continuous lines, no shading, clearly defined structures, proportions are correct, label lines do not cross and do not have arrow heads and are parallel to the top of a page, with a ruler

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22
Q

What is an eyepiece graticule?

A

Glass disk with a scale of 1 to 100, which has no units. The relative size of the divisions increase in magnification, but it remains unchanged

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23
Q

What is a stage micrometer?

A

Microscope slide with a scale in micrometers

24
Q

Explain how to calibrate a light microscope.

A

Put the stage micrometer in place and the eyepiece graticule in the eyepiece, align them
See where the scales line up on both scales, calculate the graticule division (number of micrometres/number of graticule divisions)

25
Q

How does a transmission electron microscope work?

A

A beam of electrons passed through the specimen

26
Q

What is the magnification/resolution of a TEM?

A

x500,000, 3-10nm

27
Q

How does a scanning electron microscope work?

A

A beam of electrons is sent across the surface of a specimen

28
Q

What is the magnification/resolution of a SEM?

A

x500,000, 3-10nm

29
Q

Compare light microscopes and electron microscopes.

A

Light
Small/portable
Simple sample prep
Up to x2000, 200nm
Specimens are living or dead

Electron
Expensive
Large
Complex sample prep, distorts material
Vacuum needed
Black and white images
x500,000,
Specimens are dead

30
Q

How does a laser scanning confocal microscope work?

A

Moves a spot of focused light over a specimen, fluorescence from dyed areas, which are filtered through a pinhole aperture. Only light from close is sharp, from far away it is blurry, but these both have the same focal plane, so it is not blurry

31
Q

What is the advantage of laser scanning?

A

Non invasive, used in development of new drugs

32
Q

What is a fluorescent tag? What is an advantage?

A

Glowing under UV light. Allows for more precision

33
Q

What is a cell?

A

Basic unit of all life

34
Q

What is the difference between prokaryotic and eukaryotic?

A

Prokaryotic - single celled organisms with no membrane bound organelle
Eukaryotic - multicellular organisms with membrane bound organelle

35
Q

Describe the structure of the nucleus.

A

● Surrounded by a nuclear envelope
● Nuclear pores allow substances to enter/exit.
● Dense nucleolus

36
Q

Describe the function of the nucleus.

A

● Contains DNA in the form of chromosomes.
● Controls cellular processes

37
Q

Describe the function of the nucleolus.

A

Producing ribosomes, composed of proteins and RNA, which is used to make rRNA and combined with proteins to make ribosomes

38
Q

Describe the structure and function of the endoplasmic reticulum (ER).

A

● Cisternae: network of tubules & flattened sacs extends from cell membrane & connects to nuclear envelope:
● Rough ER: many ribosomes attached for protein synthesis & transport.
● Smooth ER: lipid synthesis.

39
Q

Describe the structure and function of the Golgi apparatus.

A

● Modifies & packages proteins for export.
● Synthesises glycoproteins.

40
Q

Describe the structure and function of ribosomes.

A

Formed of protein & rRNA.
Have large subunit which joins amino acids & small subunit with mRNA binding site.
Protein synthesis.

41
Q

Describe the relationship between the organelles involved in the production and synthesis of proteins.

A

The ribosomes that synthesise proteins are attached to the rER. Vesicles transport proteins to the cis side of the Golgi apparatus, which modifies proteins for secretion via (secretory) vesicles.

42
Q

Describe the structure of a mitochondrion.

A

● Surrounded by double membrane.
● Folded inner membrane forms cristae
● Fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids, proteins.

43
Q

Describe the structure of a chloroplast.

A

● Double membrane.
● Thylakoids: flattened discs stack to form grana, containing chlorophyll
● Lamellae: tubes attach thylakoids in adjacent grana.
● Stroma: fluid-filled matrix.

44
Q

State the function of mitochondria and chloroplasts.

A

● Mitochondria: site of aerobic respiration to produce ATP.
● Chloroplasts: site of photosynthesis to convert solar energy to chemical energy.

45
Q

Describe the structure and function of a lysosome.

A

Hydrolytic enzyme removes waste products.

46
Q

Describe the structure and function of a plant cell wall.

A

● Made of cellulose (support plant)
● Plasmodesmata form pathway to allow molecules to pass between cells.
● Middle lamella separates adjacent cell walls.

47
Q

What are bacterial and fungal cell walls made of?

A

Bacteria: peptidoglycan (murein)
Fungi: chitin

48
Q

Describe the structure and function of centrioles.

A

● Spherical group of 9 microtubules arranged in a 9+2 arrangement
● Located in centrosomes.
● Migrate to opposite poles of cell during prophase & spindle fibres form between them.

49
Q

Describe the structure and function of flagella.

A

● Made of the protein flagellin.
● Rotates to move (unicellular) organism.

50
Q

Describe the structure and function of cilia.

A

● Protrusions on eukaryotic cells.
● Move back and forth rhythmically to sweep foreign substances / movement.

51
Q

Why is the cytoskeleton important?

A

● Provides mechanical strength.
● Aids transport within cells.
● Enables cell movement.

52
Q

Compare eukaryotic and prokaryotic cells.

A

Both have:
● Cell membrane
● Cytoplasm
● Ribosomes

53
Q

Contrast eukaryotic and prokaryotic cells.

A

Prokaryotic:
0.5-5µm
DNA is circular with no proteins, in the cytoplasm
Cell division occurs by binary fission - no spindle involved
70s ribosomes
No membrane bound organelles
Cell wall is made from peptidoglycan and murein

Eukaryotic:
100µm
DNA is associated with proteins, and formed into proteins (linear)
Cell division occurs by mitosis or meiosis involves spindle fibres (Separate chromosomes)
80s ribosomes
Membrane bound organelles, and not membrane bound organelles
Cell wall is present in plants (cellulose), fungi (chitin)

54
Q

Describe the structure and function of the cell-surface plasma membrane.

A

‘Fluid mosaic’ phospholipid bilayer with extrinsic & intrinsic proteins embedded.
● Acts as a barrier
● Semi permeable
● Involved in cell signalling / cell recognition.

55
Q

Explain the role of cholesterol, glycoproteins & glycolipids in the cell-surface membrane.

A

● Cholesterol: steroid molecule connects phospholipids & reduces fluidity.
● Glycoproteins: cell signalling, cell recognition (antigens) & binding cells together.
● Glycolipids: cell signalling & cell recognition.

BIOLOGY OCR A (6 decks)

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