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A level biology > cells P1 > Flashcards

cells P1 Flashcards

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1
Q

describe the structure of the nucleus

A

surrounded by a nuclear envelope
nuclear pores allow substances to enter/exit
dense nucleolus made of proteins and RNA

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2
Q

describe the function of the nucleus

A

contains genetic code for each cell

site of transcription, mitosis

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3
Q

describe the structure and function of the cell membrane

A

‘fluid mosaic’ phospholipid bilayer with intrinsic and extrinsic proteins embedded

isolates cytoplasm from extracellular enviromment
selectively permeable to regulate transport of substances

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4
Q

describe the structure and function of the rough endoplasmic reticulum

A

sheets of folded membranes forming flattened sacs called cisternae

covered in many ribosomes for protein synthesis

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5
Q

describe the structure and function of the smooth ER

A

sheets of folded membranes forming flattened sacs called cisternae

lipid synthesis

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6
Q

describe the structure of the golgi apparatus

A

a group of fluid filled, membrane bound sacs called cisternae
vesicles made by it are seen at the edges

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7
Q

describe the function of the golgi apparatus

A

processes and packages proteins and lipids
modifies them ready for release

synthesises glycoproteins

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8
Q

describe the function of the golgi vesicles

A

stores lipids and proteins, transports them out of cell via cell membrane

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9
Q

describe the structure and function of a lysosome

A

small, round membrane bound organelle.

contains hydrolytic enzymes (lysozyme) which digests the contents of phagosome

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10
Q

describe the structure and function of a ribosome

A

very small organism
either floats free in cytoplasm or is attached to RER
made of proteins and RNA
not surrounded by a membrane

PROTEIN SYNTHESIS

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11
Q

describe the structure of a mitochondrion

A

surrounded by a double membrane, inner membrane folded to form cristae (site of ETC/ oxidative phosphorylation)

fluid matrix - contains mitochondrial DNA, respiratory enzymes, lipids, proteins

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12
Q

describe the function of the mitochondria

A

site of aerobic respiration and ATP synthesis

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13
Q

describe the structure of a chloroplast

A

thylakoids - flattened discs stack to form grana which contain photosystems with chlorophyll
lamellae - tubes attract thylakoids in adjacent grana.
stroma - fluid filled matrix

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14
Q

what’s the function of a chloroplast ?

A

site of photosynthesis

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15
Q

what’s the function of a chloroplast ?

A

site of photosynthesis

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16
Q

describe the structure of the cell wall

A

bacteria: made of polysaccharide murein

plants: made of cellulose microfibrils

fungi: chitin

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17
Q

describe the functions of the cell wall

A

mechanical strength and support
physical barrier against pathogens

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18
Q

describe the functions of the cell wall

A

mechanical strength and support
physical barrier against pathogens

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19
Q

describe the structure and function of the cell vacuole in plants

A

surrounded by a single membrane
tonoplast contains cell sap (mineral ions, water, enzymes etc)

absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm

makes cell turgid and therefore provides support (prevents plants wilting)

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20
Q

contrast the structure of animal cells (A) and bacterial cells (B)

A

A has a nucleus, whereas B has free DNA

A has mitochondria, whereas B doesn’t

A has no cell wall, whereas B has a murein cell wall

A has larger ribosomes

A has no capsule whereas B has a capsule

A has DNA bound to histones, whereas B has DNA not associated with histones

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21
Q

name the 2 key differences between fungal and plant cells

A

fungal cell walls are made up of chitin rather than murein

fungal cells don’t have chloroplasts

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22
Q

name the 2 key differences between fungal and plant cells

A

fungal cell walls are made up of chitin rather than murein

fungal cells don’t have chloroplasts

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23
Q

explain some common cell adaptations

A

folded membrane or microvilli increase surface area e.g. for diffusion

many mitochondria- large amounts of ATP for active transport

walls one cell thick to reduce diffusion pathway

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24
Q

state the role of plasmids in prokaryotes

A

small ring of DNA that carries non-essential genes
can be exchanged between bacterial cells via conjugation

(not always present)

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25
Q

state the role of flagella in prokaryotes

A

rotating tail propels organism

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26
Q

state the role of the capsule in prokaryotes

A

provides protection against phagocytes and external chemicals

prevents cell from drying out (desiccating)

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27
Q

why are viruses referred to as particles instead of cells?

A

Acellular and non living - no cytoplasm

cannot self reproduce, no metabolism

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28
Q

state the role of a capsid on viral particles

A

surface sites enable viral particle to bind to and enter host cells or inject their genetic material

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29
Q

state the role of attachment proteins on virus

A

enable viral protein to bind to complementary sites on host cell

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30
Q

outline how a student could prepare a temporary mount of tissue for an optical microscope

A

obtain a thin section of tissue

place plant tissue on drop of water

stain tissue on a slide to make structures visible

add coverslip using mounted needle at 45degrees to avoid trapping air bubbles

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31
Q

suggest the advantages and limitations of using an optical microscope

A
  • colour image
  • can show living structures
  • affordable apparatus
  • but 2D image
  • lower resolution than electron microscopes
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32
Q

describe how a transmission electron microscope works

A

pass a high energy beam of electrons through a thin slice of specimen
more dense structures appear darker since they absorb more electrons

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33
Q

suggest the advantages and limitations of using a TEM

A
  • high resolution
  • high magnification
  • but 2D image
  • requires a vacuum (can’t show living - - structures)
  • no colour image
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34
Q

describe how a scanning electron microscope (SEM) works

A

focus a beam of electrons onto a specimens surface using electromagnetic lenses.
reflected electrons hit a collecting device and are amplified to produce an image

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35
Q

suggest the advantages and limitations of using a SEM

A
  • 3D image
  • high resolution
  • but requires a vacuum (can’t show living structures
  • no colour image
  • only shows outer surface
36
Q

define magnification

A

factor by which the image is larger than the actual specimen

37
Q

define resolution

A

smallest separation distance at which 2 separate structures can be distinguished from one another

38
Q

state the magnification equation

A

magnification = image size/ actual size

(I AM)

39
Q

contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells [6]

A

TEM use elections and optical use light

TEM allows a greater resolution, so smaller organelles such as ribosomes can be observed

TEM view only dead specimens, and optical can view live specimens

TEM don’t show colour and optical can

TEM requires thinner specimens

TEM focuses using magnets and optical uses lenses

40
Q

describe how a sample of chloroplasts could be isolated from leaves [4]

A

blend cells and filter in ice cold, isotonic and PH buffered solution. Spin in centrifuge and remove nuclei. Spin at higher speed and chloroplasts settle out

41
Q

explain why the solution is ice-cold, buffered and isotonic

A

ice cold to slow/stop enzyme action to prevent digestion of organelles

buffered to maintain PH so enzymes/proteins aren’t denatured

isotonic - prevents osmosis, so no shrinkage of organelles

42
Q

explain why you use a blender and filter the mixture

A

use a blender to break open the cells

filtered to remove larger debris

43
Q

outline what happens during ultracentrifugation

A

blend cells to break open the cell and filter to remove larger debris
in ice cold, isotonic and PH buffered solution.
spin homogenise in centrifuge
the most dense organelles in the mixture form a pellet
filter off the supernatant and spin again at a higher speed.

44
Q

state the order of sedimentation of organelles during centrifugation

A

nucleus —> mitochondria —> lysosomes —> RER —> plasma membrane —> SER —> ribosomes

45
Q

state the order of sedimentation of organelles during centrifugation

A

nucleus —> mitochondria —> lysosomes —> RER —> plasma membrane —> SER —> ribosomes

46
Q

the cell was stained. this caused parts of the structure of the cell-surface membrane to appear as two dark lines. suggest an explanation for the appearance of it. [3]

A

membrane has a phospholipid bilayer, stain bonds to phosphate/ glycerol, on inside and outside of membrane

47
Q

describe how you could make a temporary mount of a peice of plant tissue to observe the position of starch grains in the cell using an optical microscope [4]

A
  • add a drop of water to glass slide
  • obtain a thin section of plant tissue and place on slide
  • stain with iodine in potassium iodide
    lower cover slip using mounted needle.
48
Q

describe binary fission in bacteria [3]

A

replication of circular DNA, replication of plasmids, division of cytoplasm to produce daughter cells

49
Q

suggest and explain how 2 environmental variables could be changes to increase the growth rate of cells [4]

A

increased temperature - increased enzyme activity

increased concentration of oxygen - increases respiration

increased concentration of phosphate - increased ATP

50
Q

convert 1 micrometer to m

A

0.001 (divide by 1000)

51
Q

what is mitosis needed for?

A

the growth of multicellular organisms and for repairing damaged tissues

(asexual reproduction)

52
Q

what are the stages of the cell cycle

A
  1. interphase
  2. mitosis or meiosis
  3. cytokinesis
53
Q

what happens during interphase?

A

G1 - cell synthesises proteins for replication and new organelles made

S - DNA replication

G2 - organelles divide, more proteins made, ATP made

54
Q

outline what happens during prophase

A

chromosomes condense, becoming visible

centrioles move to opposite poles of cell and spindle fibres form.

nuclear envelope breaks down (chromosomes free in cytoplasm)

55
Q

outline what happens during metaphase

A

sister chromatids line up at cell equator attached to the spindle by their centromeres.

56
Q

outline what happens during anaphase

A

centromere’s divide, sister chromatids separate into 2 chromosomes and are pulled to opposite poles of cell (V shaped)
spindle fibres break down

57
Q

outline what happens during telephase

A

chromosomes decondense, becoming invisible again (long and thin)

new nuclear envelopes form around each set of chromosomes (2 new nuclei- each with one copy of each chromosome)

58
Q

describe the role of the spindle fire bed and the behaviour of the chromosomes during prophase, metaphase and anaphase [5]

A
  • in prophase, chromosomes condense
  • in metaphase/prophase, centromeres attach to spindle fibres
  • in metaphase, chromosomes line up in centre of cell
  • in anaphase, centromeres divide
  • in anaphase, chromatids are pulled to opposite poles of cell
59
Q

suggest why preventing the formation of spindle fibres stopped the cell cycle [2]

A

chromosomes can’t attach to spindle, so can’t line up on spindle, so no metaphase

60
Q

explain the procedure for a root tip squash experiment

A

prepare a temporary mount of root tissue

focus an optical microscope on the slide.

count total number of cells in the field of view and number of cells in a stage of mitosis

calculate mitotic index (proportion of cells undergoing mitosis)

61
Q

explain the procedure for a root tip squash experiment

A

prepare a temporary mount of root tissue

focus an optical microscope on the slide.

count total number of cells in the field of view and number of cells in a stage of mitosis

calculate mitotic index (proportion of cells undergoing mitosis)

62
Q

for the mitosis root tip experiment explain why you only used the first 5mm from the tip of an onion root

A

it’s where dividing cells are found/ where mitosis occurs

63
Q

explain why you pressed down firmly on the cover slip

A

to get a thin layer of cells so light passes through, making cells visible

64
Q

describe the appearance and behaviour of chromosomes during mitosis [5]

A
  • during prophase, chromosomes condense and become visible
  • chromosomes appear as 2 sister chromatids joined at the centromere
  • during metaphase, chromosomes line up on centre of cell, attached to spindle fibres
  • by their centromere
  • during anaphase, the centromere divides
  • and the chromosomes are pulled to opposite poles of cell
  • during telephase, the chromosomes unwind and become longer and thinner
65
Q

describe 2 aseptic techniques you would have used when transferring a sample into an agar plate

A

open lid of petri dish as little as possible, to prevent unwanted bacteria contaminating the dish

wear gloves/ wash hands to prevent contamination from bacteria on hands.

66
Q

describe the fluid mosaic model of membranes

A

fluid: phospholipid bilayer in which individual phospholipids can move

mosaic: intrinsic and extrinsic proteins embedded

67
Q

explain the role of cholesterol in membranes

A

connects phospholipids and reduces flexibility to make bilayer more stable

68
Q

explain the role of glycolipids in membranes

A

cell signalling and cell recognition

69
Q

explain the role of glycolipids in membranes

A

cell signalling and cell recognition

70
Q

explain the function of membranes within cells

A

selectively permeable to regulate passage of molecules into/ out of organelles

71
Q

name and explain 3 factors that may affect membrane permeability

A

temperature: high temperature denatures membranes proteins

PH: changes tertiary structure of membranes proteins

use of a solvent: may dissolve membrane.

72
Q

name and describe 5 ways substances can move across the cell surface membrane [5]

A

diffusion of small/non-polar molecules down a concentration gradient

facilitated diffusion down a concentration gradient via protein carrier/ channel

osmosis of water down a water potential gradient

active transport against a concentration via protein carrier using ATP

co-transport of 2 different substances using a carrier protein

73
Q

the movement of substances across cell membranes is affected by membrane structure. describe how [5]

A

cholesterol affects permeability/ fluidity

carrier proteins allow active transport

channel/ carrier proteins allow facilitation diffusion/co-transport

phospholipid bilayer allows diffusion of non-polar/lipid soluble substances

phospholipid bilayer prevents diffusion of polar/charged substances

membrane surface area/ number of channel/ carriers determines how much diffusion

74
Q

the movement of substances across cell membranes is affected by membrane structure. describe how [5]

A

cholesterol affects permeability/ fluidity

carrier proteins allow active transport

channel/ carrier proteins allow facilitation diffusion/co-transport

phospholipid bilayer allows diffusion of non-polar/lipid soluble substances

phospholipid bilayer prevents diffusion of polar/charged substances

membrane surface area/ number of channel/ carriers determines how much diffusion

75
Q

suggest and explain 2 ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients [2]

A
  • membrane folded, so increased surface area
  • large number of protein channels/ carriers in membrane for facilitated diffusion
  • large number of protein carriers in membrane for active transport
76
Q

what does the rate of facilitated diffusion depend on?

A

the concentration gradient

the number of channel/carrier proteins

77
Q

explain why simple diffusion of chloride ions across a cell-surface membrane would be extremely slow

A

ions are water soluble and the centre of the phospholipid bilayer is hydrophobic

78
Q

chloride ions in the cell aren’t immediately used up. describe what will happen to the rate of facilitated diffusion of the chloride ions into the cell over time

A

the rate of facilitated diffusion will slow down/level off.
as diffusion progresses, the concentration gradient of the chloride ions will decrease over time until an equilibrium is reached

79
Q

name factors that affect the rate of diffusion

A

temperature
diffusion distance
surface area
size of molecule
concentration gradient

80
Q

contrast the processes of active transport and facilitated diffusion [3]

A

facilitated diffusion involves channel/carrier proteins, whereas active transport only involves carrier proteins

Facilitated diffusion doesn’t use ATP whereas active transport uses ATP

facilitated diffusion takes place down a concentration gradient whereas active transport can occur against a concentration gradient

81
Q

compare and contrast the processes by which water and inorganic ions enter cells [3]

A
  • both move down concentration gradient
  • both move through protein channels in membranes
  • ions can move against a concentration gradient by active transport
82
Q

explain the function of ATP hydrolase when linked to the action of a carrier protein [2]

A

breaks down ATP into ADP and Pi which releases energy
this energy allows the active transport of ions

83
Q

the movement of sodium ions out of the cell allows the absorption of glucose into the cell lining the ileum. explain how [2]

A

it maintains a concentration gradient for NA+ from ileum into cell
NA+ moving in by co-transport, brings glucose with it

84
Q

explain how co-transport is involved in the absorption of glucose/amino acids in the small intestine

A

Na+ is actively transported out of epithelial cells into bloodstream.

Na+ concentration is lower in epithelial cells than lumen of gut

transport of glucose/amino acids from lumen to epithelial cells is coupled to facilitated diffusion of Na+ down electrochemical gradient

85
Q

what does the rate of osmosis depend on?

A

the water potential gradient

thickness of exchange surface

surface area of exchange surface

86
Q

what are the factors affecting the rate of active transport?

A

the number of carrier proteins

the speed of the individual carrier proteins

the rate of respiration in the cell and availability of ATP

87
Q

suggest one explanation for the faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration [2]

A
  • amino acids used in respiration
  • so more energy/ATP for plasmid replication

OR

  • amino acids are used in respiration
  • so more energy/ ATP for plasmid replication

A level biology (6 decks)

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