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HNC Applied Science in Biology and Chemistry > Cell Biology - Outcome 1 > Flashcards

Cell Biology - Outcome 1 Flashcards

Structure and Function of the Cell Membrane and Eukaryotic Organelles

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1
Q

what is the definition of a prokaryote ?

A

does not have true nucleus

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2
Q

what is the definition of a eukaryote?

A

has a true nucleus

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3
Q

what is the definition of unicellular?

A

single-celled organism

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4
Q

what is the definition of multicellular?

A

multi-celled organism

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5
Q

what is the definition of an organelle?

A

membrane-bound component of cell that performs specific function

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6
Q

what type of organism contains no membrane-bound organelles?

A

prokaryotes

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7
Q

which organism is bigger in size, eukaryote or prokaryote?

A

eukaryote is bigger in size and prokaryote is smaller in size

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8
Q

what type of organism DOES contain membrane-bound organelles?

A

eukaryotes

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9
Q

what do eukaryotes contain, and where is it contained?

A

membrane-bound nucleus, contains multiple chromosomes which are contained within nucleus

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10
Q

what does NOT exist in eukaryotes?

A

plasmids

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11
Q

eukaryotes can be what?

A

single-celled or multi-celled

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12
Q

what is an example of a prokaryote?

A

bacteria

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13
Q

what is an example of a eukaryote?

A

animal cell, plant cell and fungi

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14
Q

eukaryotes contain internal membranes in forms of what?

A

organelles

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15
Q

what do cells need to survive? and what must it all remove?

A

it needs oxygen, water and energy to survive and it must also remove carbon dioxide as a waste material.

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16
Q

how can cells exchange materials?

A

with the environment

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17
Q

what happens if the cell does not exchange materials efficiently?

A

cell will be deprived of oxygen and nutrients, it will then become poisoned from build up of toxic waste materials

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18
Q

what is the cell membrane composed of?

A

lipids and proteins

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19
Q

what is the cell membrane classed as?

A

semi-permeable

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20
Q

what is the function of the cell membrane?

A

controls what enters and exits the cell

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21
Q

what does the nucleus contain and in what form?

A

contains genetic material (DNA) in the form of chromatin

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22
Q

what happens to chromatin in cell division?

A

it organises itself into sets of chromosomes

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23
Q

what is the nucleus bounded by and what does it create?

A

double inner membranes, the outer and inner membrane which fuse at certain points to create nuclear pores

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24
Q

what are nuclear pores necessary for?

A

transport of materials in and out of nucleus

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25
Q

what is the structure within the nucleus called and what is its function?

A

nucleolus, a sub-organelle where ribosomes are assembled

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26
Q

what is the mitochondrion the site of?

A

energy production/respiration

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27
Q

what is cristae and what does it provide?

A

folded inner-membrane that creates finger-like projections, provides increased surface area for chemical reactions

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28
Q

what does the mitochondrion provide?

A

an environment for the conversion of nutrients into adenosine triphosphate (ATP)

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29
Q

what is the endoplasmic reticulum (ER)?

A

a series of interconnected flattened membranes within the cytosol where its surface can be embedded with ribosomes or not

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30
Q

what is the rough endoplasmic reticulum (RER)?

A

a part of the ER where ribosomes are attached and that it is involved in protein synthesis.

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31
Q

what happens when a protein is synthesised?

A

it is imported into the RER, assembled and folded and is then sent to the Golgi apparatus.

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32
Q

what is the smooth endoplasmic reticulum (SER)?

A

a part of the ER where no ribosomes are attached and is not involved in protein synthesis

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33
Q

what is the function of the SER?

A

site of lipid and steroid (fats and hormones) synthesis and detoxification of poisons

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34
Q

what is the Golgi apparatus?

A

series of membrane sacs

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35
Q

what happens at the Golgi apparatus?

A

proteins are modified and packaged here

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36
Q

what happens when a protein matures at the Golgi apparatus?

A

mature protein ‘buds’ off Golgi and is packaged into Golgi vesicle, which is then taken to cell membrane for secretion

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37
Q

what happens when the Golgi vesicle is at the cell membrane?

A

vesicle fuses with cell membrane and protein is secreted by exocytosis

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38
Q

how does a protein move through the cell?

A

in co-ordinated steps, moving from one organelle to another until it becomes a mature protein

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39
Q

what happens if a protein is coded for a location elsewhere in the body?

A

it is secreted by the synthesising cell

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40
Q

what is the secretory pathway?

A

passage from the RER to the cell membrane

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41
Q

what are lysosomes and what do they contain?

A

small membrane-bound sacs that contain digestive enzymes called lysozymes

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42
Q

what is the function of a lysozyme?

A

to break down foreign materials/damaged cells

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43
Q

what is the pH of a lysosome?

A

pH 2

44
Q

what are peroxisomes?

A

oxidative organelles that use oxygen molecules to form hydrogen peroxide

45
Q

what are peroxisomes involved in?

A

detoxification of poisons eg. alcohol

involved in breakdown of fatty acid chains

46
Q

what is the cytoskeleton?

A

structural component of a cell

47
Q

what does the cytoskeleton provide and what is it provided by?

A

provides internal support and this is provided by protein fibres of the cytoskeleton

48
Q

what are the 3 types of protein fibres of the cytoskeleton?

A
  • microfilaments (actin)
  • intermediate filaments
  • microtubules
49
Q

what are microfilaments (actin) involved in?

A

cell division

50
Q

what do intermediate filaments provide?

A

tensile strength and anchorage

51
Q

what are microtubules involved in?

A
  • being a set of tracks for newly synthesised proteins
  • creation of spindle fibres during cell division
52
Q

what is the overall function of the cytoskeleton?

A
  • maintaining cell shape
  • co-ordinating cell division
  • cell movement
  • organisation of organelles
53
Q

what may eukaryotic cells have?

A

flagella

54
Q

what is flagella made of?

A

microtubules

55
Q

what are microtubules composed of?

A

the protein tubulin

56
Q

what organelle is found in plant cells but NOT animal cells?

A

cell wall

57
Q

what is a fungal cell wall composed of?

A

chitin

58
Q

what is a plant and algal cell wall made of?

A

cellulose

59
Q

what is a bacterial cell wall made of?

A

peptidoglycan

60
Q

what is the function of the cell wall?

A

provides mechanical protection and is freely permeable

61
Q

what is the function of chloroplasts?

A

site of photosynthesis

62
Q

what is the equation for photosynthesis?

A

carbon dioxide + water + light energy -> oxygen + glucose

63
Q

what green pigment is used to trap sunlight so that plants can photosynthesise?

A

chlorophyll

64
Q

what is a plant vacuole?

A

a membrane bound sac within the cytoplasm

65
Q

how much space does a plant vacuole take up?

A

80%

66
Q

what is a plant vacuole filled with?

A

cell sap and water

67
Q

what is the function of a plant vacuole?

A

maintains plant cell turgor pressure which is necessary to support plant and keep it upright

68
Q

animal cells also have vacuoles, but what are their functions?

A

temporary storage of materials and transport of materials

69
Q

how does the cell membrane separate contents from surrounding environment?

A

by forming a permeability barrier between all contents and extracellular environment.

70
Q

what molecules does the cell membrane allow to move in and out freely?

A

respiratory gases

71
Q

how does the cell membrane transport ions and glucose across membrane

A

by requiring mechanisms in the form of proteins

72
Q

the cell membrane is said to be selectively permeable, what does this mean?

A
  • controls what goes in and out
  • controls what direction they move in
  • maintains constant internal environment
  • forms water insoluble barrier between ER and IR
73
Q

what is the most abundant cell in the cell membrane?

A

phospholipids

74
Q

what are phospholipids?

A

viscous solvents where proteins can be inserted/attached/integrated.
composed of 2 FA hydrocarbon chain attached to glycerol molecule and with phosphate group bonded to carbon no.3 on glycerol molecule by ester bond

75
Q

what does amphipathic mean?

A

they have both polar and non-polar groups

76
Q

how are phospholipids organised in the bilayer?

A

with their hydrophobic tails facing each other

creates barrier between aqueous cell contents and aqueous environments ie. stops free movement of water

77
Q

what are phosphoglycerides?

A

phospholipids with additional amino acid group

78
Q

what is sphingolipid in the membrane known as?

A

sphingomyelin

79
Q

what are sphingomyelin involved in and what cell are they most abundant in?

A

neuron cells

80
Q

what is sphingomyelin composed of?

A

1 FA tail which is parallel to the sphingosine tail where the phosphate group is attached

81
Q

what is linked to the phosphate group in sphingomyelin?

A

a choline molecule that forms the head of the molecule

82
Q

what is attached to a glycolipid?

A

a carbohydrate group

83
Q

how is the carbohydrate group in a glycolipid bonded to the lipid component?

A

via glycosidic bond

84
Q

what is the purpose of a glycolipid?

A

to stick out from the membrane and serve as markers for cell recognition

85
Q

what is cholesterol?

A

another type of lipid found in the membrane

86
Q

how many cholesterols are there per phospholipid in the membrane?

A

1

87
Q

what type of membranes do not contain cholesterol?

A

bacterial membranes

88
Q

how does cholesterol affect the permeability of the cell membrane to small water-soluble molecules?

A

they decrease the permeability

89
Q

what would happen if there was no cholesterol in the membrane?

A

cells would need a cell wall

90
Q

what does the amount of cholesterol determine?

A

how rigid the membrane will be

91
Q

how can lipids move within the membrane?

A
  • laterally (sideways)
  • transversely (‘flip-flop’ across membrane
92
Q

what does the composition of a membrane determine?

A

how much the membrane can move (fluidity)

93
Q

what factors affect fluidity of the membrane?

A
  • temperature
  • cholesterol content
  • saturation
94
Q

how does temperature affect fluidity of membrane ?

A

decreased temperature means less energy for phospholipids
phospholipids stay more compacted
decrease fluidity

increased temperature means more energy for phospholipids
phospholipids move around more
increased fluidity

95
Q

how does cholesterol content affect fluidity of membrane?

A

without cholesterol, membrane would be too fluid and would be at risk of leaking, reducing the barrier
cholesterol inserts itself between FA tails of lipid molecules, this decreases phospholipid movement making membrane more rigid, decreasing fluidity

96
Q

how does cholesterol content affect membrane fluidity when put with low temperature?

A

cholesterol stops hydrocarbon tails crystallising (freezing), this helps maintain and increase fluidity

97
Q

how does saturation affect membrane fluidity?

A

FA tail of phospholipids may be straight or ‘kinked’, this is determined by carbon bonds

saturated FA have no carbon to carbon double bonds (only single bonds), making the tail appear straight

unsaturated FA have one or more carbon to carbon double bond, making tail appear kinked

98
Q

what happens in unsaturated phospholipids and what does it result in?

A

the kink in fatty acid tail increases the space between phospholipid molecules, more space to move around through membrane, more fluid

results in a thin, fluid liquid solution

99
Q

what happens in saturated phospholipids and what does it result in?

A

the straight fatty acid tail results in lipid being able to be more compacted together, less space to move around through membrane, less fluid

results in more viscous liquid solution

100
Q

describe the main points on the importance of membrane fluidity

A
  • to adjust to the surrounding environment
    (may have to adapt shape in order to fit a space)
    (may have to adapt in response to pressure)
  • allows membrane to be quickly repaired if damaged
  • can move to allow entry and exit of ions
  • has ability to merge with organelle membranes
101
Q

what are the three main types of membrane proteins?

A
  • transmembrane
  • peripheral
  • integral
102
Q

what are the features of a transmembrane protein?

A
  • cross membrane completely
  • may span it once or several times
  • region embedded into membrane is hydrophobic with a-helice formation
  • a-helice formation will be linked by hydrophilic regions which protrude into extracellular or intracellular environment
103
Q

what are the features of an integral protein?

A
  • embedded into the membrane
  • do not span membrane completely
104
Q

what are the features of a peripheral protein attached on the outside cell surface?

A
  • becomes part of extracellular matrix (connective tissue)
  • surrounds and supports cells
105
Q

what are the features of a peripheral protein attached on the inside cell surface?

A
  • protein becomes part of cytoskeleton
106
Q

what are the functions of membrane proteins and describe them?

A

transport
- moving materials in and out (through pores or by forming pumps)

receptors
- allows cell to respond to its environment
- convey messages from outside the cell to inside cell

cell markers
- each organism has own unique ones which helps immune system to identify invaders

107
Q

membrane composition varies between cell types, what are some examples of this?

A
  • white blood cells have high amount of proteins which act as cell markers and receptor
  • neuron cells have higher sphingomyelin content in their membranes
  • the more saturated lipids, more fluidity

HNC Applied Science in Biology and Chemistry (4 decks)

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