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A Level Biology OCR A > 2.1 Cell Structure > Flashcards

2.1 Cell Structure Flashcards

1
Q

what is magnification?

A

how much bigger an image appears compared to the original object

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2
Q

what is resolution?

A

the ability to distinguish between two points of an image

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3
Q

what are light microscopes also known as?

A

optical microscopes

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4
Q

what are the advantages of light microscopes?

A

cheap, easy to use, portable, can study whole living specimens

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5
Q

what is the maximum magnification of a light microscope?

A

x2000

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6
Q

can light microscopes be used to view organelles such as ribosomes?

A

no, the resolution is not high enough

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7
Q

how do you calculate total magnification using the lenses?

A

magnifying power of objective lens x magnifying power of eyepiece lens

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8
Q

what is a photomicrograph?

A

a photograph of the image from an optical microscope

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9
Q

what are laser scanning microscopes also known as?

A

confocal microscopes

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10
Q

how do laser scanning microscopes form images?

A

laser light scans an object point by point and a computer assembles them into pixels on a screen

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11
Q

what are the advantages of laser scanning microscopes?

A

high resolution, depth selectivity (can view cells but also whole living specimens)

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12
Q

how are laser scanning microscopes used in medicine?

A

in biological research and to identify pathogens, specifically fungi, for fast diagnosis and treatment

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13
Q

what are the two types of electron microscopes?

A

transmission electron microscopes and scanning electron microscopes

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14
Q

what is the maximum magnification of a transmission electron microscope?

A

x 2 million

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15
Q

what kind of image do transmission electron microscopes form?

A

2D black and white / greyscale image

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16
Q

what is an electron micrograph?

A

photo of an image produced by an electron microscope

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17
Q

what is the maximum magnification of a scanning electron microscope?

A

x 200 000

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18
Q

what kind of image do scanning electron microscopes form?

A

3D black and white / greyscale image but colour can be artificially added using computer software

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19
Q

what are the advantages of electron microscopes?

A

extremely high resolution and magnification and so give very clear and magnified images

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20
Q

what are the disadvantages of electron microscopes?

A

large, expensive, require training to use, specimens must be dead as they are viewed in a vacuum, metallic salt stains potentially hazardous to user

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21
Q

what is differential staining?

A

using stains that bind to specific cell structures to easily identify them

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22
Q

what does acetic urchin stain?

A

DNA, stains chromosomes dark red

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23
Q

what does eosin stain?

A

cytoplasm

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24
Q

what does Sudan red stain?

A

lipids

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25
Q

what does iodine stain?

A

stains starch blue-black via potassium iodide solution

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26
Q

why are some specimens embedded in wax?

A

to prevent distortion during slicing

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27
Q

what is the magnification equation?

A

AIM (image / actual)

28
Q

how can objects under a light microscope be measured?

A

using a stage graticule and an eyepiece graticule

29
Q

what is the purpose of membranes within cells?

A

keeps each organelle separate from the rest of the cell

30
Q

what is the structure of the nucleus?

A

surrounded by a double membrane (nuclear envelope), nucleolus containing RNA is not membrane bound

31
Q

what is the function of the nucleus?

A

stores genome of the organism, provides instructions for protein synthesis, control centre of the cell

32
Q

what is the function of the rough endoplasmic reticulum?

A

coated with ribosomes, provides a large surface area for ribosomes to assemble amino acids into proteins

33
Q

what is the structure of the rough endoplasmic reticulum?

A

made up of fluid filled cisternae, coated with ribosomes

34
Q

what is the function of the smooth endoplasmic reticulum?

A

synthesis of lipids, cholesterol, steroid hormones

35
Q

what is the structure of the smooth endoplasmic reticulum?

A

made up of fluid filled cisternae, no ribosomes on its surface

36
Q

what is the function of the Golgi apparatus?

A

modifies then packages proteins into vesicles

37
Q

what is the structure of the Golgi apparatus?

A

a stack of membrane bound flattened sacs

38
Q

how does the Golgi apparatus modify proteins?

A

adds sugar molecules to make glycoproteins, adds lipid molecules to make lipoproteins, folds proteins into their 3D shape

39
Q

what is the function of the mitochondria?

A

the site of ATP production

40
Q

where are mitochondria abundant?

A

cells where much metabolic activity takes places such as liver cells and sperm cells

41
Q

what is the structure of the mitochondria?

A

double membraned, inner membrane folded into Cristae, inside is a fluid filled matrix

42
Q

what is the function of the chloroplasts?

A

the site of photosynthesis

43
Q

what is the structure of the chloroplasts?

A

double membraned, inner membrane has thylakoids (stacks of plates) made of grana stacked on top of each other, inside is the fluid filled stroma

44
Q

what is the function of the vacuole?

A

filled with water and solutes, pushes against cell wall to maintain cell rigidity and keep it turgid

45
Q

what is the structure of the vacuole?

A

surrounded by a membrane called the tonoplast

46
Q

what is the function of the lysosome?

A

keeps powerful hydrolytic enzymes separate from the rest of the cell, can engulf old cell organelles and return digested components to the cell for reuse

47
Q

what is the structure of the lysosome?

A

small bags formed from Golgi apparatus

48
Q

where are lysosomes abundant?

A

phagocytic cells (macrophages and neutrophils) to allow them to engulf and digest pathogens

49
Q

what is the function of the cilia and the undulipodia?

A

epithelial cells have many cilia to beat mucus, nearly all cell types in the body have a cilium that acts as an antenna and allows the cell to detect signals about its immediate environment

50
Q

what is the only human cell with an undulipodium?

A

a spermatozoon

51
Q

what is the structure of the cilia and undulipodia?

A

contain microtubules and formed from centrioles

52
Q

what is the function of the ribosomes?

A

ribosomes bound to the rough endoplasmic reticulum synthesise proteins for use outside of the cell, ribosomes free in the cytoplasm synthesis proteins for use within the cell

53
Q

what is the structure of the ribosomes?

A

not membrane bound, made in the nucleus as two separate parts which pass through the nuclear envelope into the cytoplasm and combine

54
Q

what is the function of the centrioles?

A

form the spindle in cell division, involved in the formation of cilia and undulipodia

55
Q

what is the structure of the centrioles?

A

made of two bundles of microtubules at right angles to each other

56
Q

what is the function of the cytoskeleton?

A

form the track along which motor proteins drag organelles from one part of the cell to another, form the spindle before a cell divides, keep cell’s shape stable, extend between cells to enable cell-cell signalling or allow cells to adhere to a basement membrane (stabilising tissue)

57
Q

what is the structure of the cytoskeleton?

A

made up of microfilaments which are made of actin

58
Q

what is the function of the cellulose cell wall?

A

prevents turgid cells from bursting, provide strength and support, maintain the cell’s shape, permeable and allow solutions to pass through

59
Q

what are the cell walls in fungi made of?

A

chitin

60
Q

what is the structure of the cell wall?

A

made from bundles of cellulose fibres

61
Q

how do genes code for proteins?

A
  1. genes contain instructions for protein synthesis but are too large to leave the nucleus
  2. gene copied on mRNA, this process is transcription
  3. mRNA leaves nucleus via nuclear pore and enters cytoplasm
  4. mRNA finds and attaches to a ribosome on the RER
  5. Ribosome translates instructions encoded onto the length of mRNA and assembles amino acids
  6. protein molecules pinched off in vesicles and transported to the Golgi apparatus
  7. vesicle fuses with the Golgi apparatus, which modifies the protein if needed and packages the protein molecules into vesicles again
  8. vesicles travel towards and fuse with the plasma membrane
  9. plasma membrane opens to release protein molecules, this process is exocytosis
62
Q

how are prokaryotic cells different to eukaryotic cells?

A

smaller, no centrioles, no nucleus, no membrane bound organelles, wall made of peptidoglycan, smaller ribosomes, naked DNA

63
Q

are there any additional features prokaryotic cells have that eukaryotic cells do not?

A

waxy capsule surrounding cell wall, plasmids, flagella, pili

64
Q

what are pili?

A

hair-like projections that allow bacteria to adhere to host cells or each other and allow the passage of plasmid DNA from one cell to another

65
Q

by which process do prokaryotic cells divide?

A

binary fission

A Level Biology OCR A (17 decks)

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