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Biology A level > 2.1.1 cell structure > Flashcards

2.1.1 cell structure Flashcards

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1
Q

what is the function of the plasma membrane

A

controls what enters and leaves the cells and has receptors for cell signalling and responding to chemicals.

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2
Q

what is the cell wall

A

a rigid structure which surrounds plant cells. plant cell walls are made of cellulose.

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3
Q

what is the function of a cell wall

A

supports the cell

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4
Q

what is the nucleus

A

a large organelle surrounded by a nuclear envelope which has pores. it contains all the DNA . it contains a nucleolus.

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5
Q

what is the function of a lysosome

A

it contains digestive enzymes to digest invading cells and break down worn-out components. these enzymes are separated from cytoplasm via a membrane

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6
Q

what is a ribosome

A

a small organelle that floats freely or is attached to rough endoplasmic reticulum. made of proteins and RNA.

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7
Q

what is the function of a ribosome

A

the site where proteins are made

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8
Q

what is the rough endoplasmic reticulum

A

a system of membranes enclosing a fluid filled space. it is covered in ribosomes

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9
Q

what is the function of the rough endoplasmic reticulum

A

it folds and processes proteins made at the ribosomes

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10
Q

what is the smooth endoplasmic reticulum

A

a system of membranes enclosing a fluid filled space.

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11
Q

what is the function of the smooth endoplasmic reticulum

A

synthesises and processes lipids

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12
Q

what is a vesicle

A

a fluid filled sac in the cytoplasm that is surrounded by a membrane

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13
Q

what is the function of a vesicle

A

transports substances in and out of the cell via the plasma membrane or between organelles.

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14
Q

what is the Golgi apparatus

A

a group of fluid filled flattened sacs, vesicles are often found at the edges

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15
Q

what is the function of the Golgi apparatus

A

packages and processes new lipids and proteins and makes lysosomes

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16
Q

what is the function of mitochondria

A

the site of aerobic respiration where ATP is produced

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16
Q

what is mitochondria

A

they are oval shaped and have a double membrane. the inner membrane is folded to create cristae. the inside is called the matrix which contains enzymes used in respiration

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17
Q

what is a chloroplast

A

a small flattened structure found in plants. it is surrounded by a double membrane and has thylakoid membranes inside which are stacked up to form grana which are linked together by lamellae.

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18
Q

what is the function of a chloroplast

A

the site where photosynthesis takes place.

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19
Q

what is a centriole

A

small hollow cylinders made of microtubules found in animal cells

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20
Q

what is the function of a centriole

A

involved in the separation of chromosomes in cell division

21
Q

what is cilia

A

small hair like structures found on the cell membrane of some animal cells. they have an outer membrane and a ring of 9 pairs of microtubules with 2 microtubules in the middle.

22
Q

what is the function of cilia

A

the microtubules allow them to move so they can move substances along the cell surface.

23
Q

what is the function of flagella

A

microtubules contract to move the flagellum. this propels the cell forward

23
Q

what is flagella

A

have 9 pairs of microtubules around the edge and 2 in the middle. are longer than cilia

24
Q

how are organelles involved in protein production

A
  1. ribosomes synthesise proteins
  2. proteins produces at ribosomes on the RER are processed and folded by the RER
  3. they are transported to the Golgi apparatus
  4. the Golgi apparatus processes and packages the proteins into vesicles to be transported round the cell.
25
Q

what is the cytoskeleton

A

a network of protein threads in the cytoplasm. in eukaryotic cells they are microfilaments and microtubules

26
Q

what are the functions of the cytoskeleton.

A
  1. support organelles and keep them in place
  2. strengthen cell to maintain shape
  3. movement of materials inside cells
  4. movement of cell itself
27
Q

why is the cytoskeleton said to be dynamic

A

it changes in response to the environment to carry out its functions

28
Q

what is the difference in size between Eukaryotic and prokaryotic cells

A

eukaryotic cells are larger (10-100 micrometres). prokaryotic cells are less the 2 micrometres

29
Q

how is DNA different in eukaryotic and prokaryotic cells.

A

eukaryotic cells have linear DNA enclosed in a nucleus and prokaryotic cells have circular DNA called plasmids which are free in the cytoplasm

30
Q

how is the cell wall different in eukaryotic and prokaryotic cells

A

it is made of chitin (fungi) or cellulose (plants) in eukaryotic cells. in prokaryotic cells it is a different polysaccharide.

31
Q

which type of cell does not contain membrane bound organelles

A

prokaryotic cells

32
Q

how is the arrangement of the flagella different in eukaryotic and prokaryotic cells

A

in eukaryotic cells it is in the 9+2 arrangement of microtubules and in prokaryotic cells it is arranged as a helix

33
Q

which type of cell has larger ribosomes

A

eukaryotic cells (80s rather than 70s)

34
Q

define magnification

A

how much bigger the image is than the actual specimen

35
Q

define resolution

A

how well it can distinguish between two objects close together

36
Q

what is the equation for magnification

A

magnification = image size/object size

37
Q

what is the resolution and magnification of a light microscope

A

resolution: 0.2 micrometres
magnification: x1500

38
Q

how does a laser scanning confocal microscope work

A
  1. laser beams scan the specimen which is tagged by a fluorescent dye. the laser causes the dye to give off light.
  2. the light is focused through a pinhole to a detector hooked up to a computer that generates an image (3D)
  3. they produce a clearer image than a normal light microscope as out of focus light is blocked
39
Q

why do we use a laser scanning confocal microscope

A

it can be used to look at objects at different depths in thick specimens

40
Q

what are the two types of electron microscope

A

scanning and transmission

41
Q

how does a scanning electron microscope work

A

a beam of electrons is scanned across the surface of the specimen. this knocks electrons off the specimen which are collected in a cathode ray tube to form an image, the images produced are 3D

42
Q

what is the resolution and magnification of a scanning electron microscope

A

resolution: 0.002 micrometres
magnification: less than x 500 000

43
Q

how does a transmission electron microscope work

A

a focused beam of electrons is passed through the specimen. denser parts of the specimen absorb more electrons making them look darker in the image. specimen must me thin and image is 2D

44
Q

what is the resolution and magnification of a transmission electron microscope

A

resolution: 0.0002 micrometres
magnification: can be more than x1 000 000

45
Q

why do we stain specimen

A

increases the contrast and allows transparent components to be picked up in the image

46
Q

how do we stain for light microscopes

A

we use a dye. different parts of the specimen absorb different amounts of dye so it increases contrast. we can use different dyes at the same time.

47
Q

how do we stain for electron microscopes

A

specimen dipped in heavy metal like lead, metal ions spread the electrons increasing contrast.

48
Q

how do we prepare a microscope slide

A
  1. take thin slice of specimen
  2. use tweezers to place on the slide
  3. on a wet mount we add a drop of water on the slide before placing specimen.
  4. gently add the cover slip at a tilt to prevent air bubbles.
49
Q

how do we use a microscope

A
  1. clip slide in place
  2. select lowest powered objective lens
  3. use coarse adjustment knob to bring the stage up until image is roughly in focus
  4. use fine adjustment knob to get a clear image
  5. increase magnification by moving up an objective lens and refocusing.
50
Q

how do we calibrate an eyepiece graticule

A

Line up the zero of the eyepiece graticule and the zero of the stage micrometer.
Make sure the scales are parallel.
Look at the scales and see where they are in line again.
see how many micrometres each division of the eyepiece graticule is. we use magnification x number of divisions of stage micrometer.

Biology A level (13 decks)

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