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Biology > 2.1 Cell Structure and 2.5 Biological Membranes > Flashcards

2.1 Cell Structure and 2.5 Biological Membranes Flashcards

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1
Q

What is the definition of magnification?

A

How many times bigger the image is than the actual size of the object.

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2
Q

What is the definition of resolution?

A

The ability to separate two objects, visually.

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3
Q

What is a light microscope used to look at?

A

Whole cells and tissues.

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4
Q

What are the advantages of a light microscope?

A

Relatively cheap, easy to use, portable, can be used to observe living specimens, colour images produced.

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5
Q

What is a disadvantage of a light microscope?

A

Smaller magnification and resolution so very small structures cannot be seen.

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6
Q

How does a light microscope work?

A

Uses a number of lenses, light passes through condenser and specimen, light beam is focused though lenses.

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7
Q

What is a Transmission Electron Microscope used to look at?

A

Subcellular structures (organelles).

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8
Q

What are the advantages of a TEM?

A

Increased resolution due to wavelength being shorter than visual light, better magnification and resolution, able to see smaller organelles.

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9
Q

What are the disadvantages of a TEM/SEM?

A

Expensive, not portable, skilled training needed, vacuum needed to prepare slides which is a complex process.

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10
Q

How does a TEM work?

A

Generates beams of electrons which pass through thin areas of sample easier to create contrast, sample dehydrated and stained, electrons focused on photographic plate.

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11
Q

What is a Scanning Electron Microscope used to look at?

A

Cell surfaces.

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12
Q

What are the advantages of an SEM?

A

Can see surface features in detail, better magnification and resolution than LM, 3D greyscale image produced.

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13
Q

How does a SEM work?

A

Electrons are reflected off the surface of (metal salt) stained sample in a vacuum.

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14
Q

Why is the resolution of a light microscope limited?

A

The wavelength of visible light is 400-700 nm.

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15
Q

What is the role of the objective lens?

A

Focus the image.

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16
Q

What is the role of the coverslip?

A

To be placed over the specimen and protect the lens.

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17
Q

What is the role of the microscope slide?

A

To place the specimen onto.

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18
Q

What is the role of the light source and mirror?

A

To reflect light up through the lens and eyepiece.

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19
Q

Why are specimens stained?

A

To make the components of a cell easier to identify (differential staining) and provide contrast against the background to make the structures more visible.

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20
Q

How is a light microscope specimen prepared?

A

Fix in wax if fragile, slice to allow light to pass through.

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21
Q

How is an electron microscope specimen prepared?

A

Fix in glutaraldehyde, dehydrate with ethanol, embed in resin, slice thinly, stain with heavy metal, put on copper grid, place in vacuum.

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22
Q

Why must EM specimens be put in a vacuum before viewing?

A

So that air particles don’t get in the way of the electrons.

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23
Q

What is the magnification equation?

A

image size = object size x magnification

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24
Q

What features do animal and plant cells share?

A

Ribosomes, nucleus, cytoplasm, mitochondria, RER, SER, cell surface membrane, vesicles, golgi apparatus, nucleolus.

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25
Q

What features are specific to plant cells?

A

Permanent vacuole, cellulose cell wall, chloroplasts.

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26
Q

What features are specific to animal cells?

A

Centrioles, lysosome.

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27
Q

What is a nucleus?

A

Largest organelle, surrounded by nuclear envelope, contains nucleolus.

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28
Q

What is the function of a nucleus?

A

Stores DNA as chromatin, site of DNA replication, controls protein synthesis and cell activity.

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29
Q

What is a nucleolus?

A

Small, dark structure in the nucleus.

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30
Q

What is the function of a nucleolus?

A

Synthesis of ribosomes.

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31
Q

What is a Rough Endoplasmic Reticulum?

A

Series of membranes folded up (cisternae), space between filled with fluid that transports substances, studded with ribosomes.

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32
Q

What is the function of a Rough Endoplasmic Reticulum?

A

Synthesis of ribosomes, Synthesis of proteins.

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33
Q

What is a Smooth Endoplasmic Reticulum?

A

Series of membranes folded up (cisternae) space between filled with fluid that transports substances.

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34
Q

What is the function of a Smooth Endoplasmic Reticulum?

A

Synthesis of lipids.

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35
Q

What is a golgi apparatus?

A

Series of membranes folded up (cisternae), appears as flattened sacks, surrounded by vesicles.

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36
Q

What is the function of a golgi apparatus?

A

Processes all substances produced by RER and SER, creates vesicles.

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37
Q

What is a ribosome?

A

Tiny organelle with light subunit and heavy subunit.

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38
Q

What is the function of a ribosome?

A

Either float free in cytoplasm or attached to RER, site of protein synthesis.

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39
Q

What is a lysosome?

A

Small, round organelles, contain digestive enzymes which need to be kept separate from the rest of the cell by a membrane, specific type of vesicle.

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40
Q

What is the function of a lysosome?

A

Use digestive enzymes to digest invading cells or even destroy the cell itself when required.

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41
Q

What is a vesicle?

A

Membrane bags that contain things, made by the golgi apparatus.

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42
Q

What is the function of a vesicle?

A

(Depending on type) move molecules, secrete substances, digest materials, or regulate the pressure in the cell.

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43
Q

What is a chloroplast?

A

Double membrane bound organelle, more membranes inside cell (thylakoid) which can be stacked (grana) with long ones joining them (lamellae), contains stroma (cytoplasm), loop of DNA, and chlorophyll.

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44
Q

What is the function of a chloroplast?

A

Site of photosynthesis.

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45
Q

What is a mitochondrion?

A

Double membrane bound organelle, inner membrane folds to produce cristae, contains matrix (cytoplasm), can appear oval or circular depending on cross-section, contains loop of DNA.

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46
Q

What is the function of a mitochondrion?

A

Site of aerobic respiration, makes ATP in the cristae.

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47
Q

What is a cellulose cell wall?

A

Made of polysaccharide cellulose (in plants), has pores called plasmodesmata.

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48
Q

What is the function of a cellulose cell wall?

A

Gives the cell support, can be a carbohydrate store, plasmodesmata connects two cells together by their cytoplasm allowing exchange of substances.

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49
Q

What is a centriole?

A

Two bundles of mitochondria at right angles to each other.

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50
Q

What is the function of a centriole?

A

Essential to division (enables movement of chromosomes), movement of substances, formation of cilia and undulipodia.

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51
Q

What is a permanent vacuole?

A

Membrane containing liquid, pigments, waste etc.

52
Q

What is the function of a permanent vacuole?

A

Keeps the cell turgid (full and the right shape) which gives support, stores water.

53
Q

What is a cytoskeleton?

A

Microtubules, move using protein motors, microfilaments.

54
Q

What is the role of a cytoskeleton?

A

Cell support movement of cilia, flagella or whole cell, changing cell shape (cytokinesis, phagocytosis, endocytosis and exocytosis) muscle contraction, organelles moved or held in place, movement of chromosomes.

55
Q

Where is a cytoskeleton present?

A

All eukaryotic cells.

56
Q

What are peroxisomes?

A

Vesicles that usually contain enzymes such as catalase, moved around the cell by attaching to cytoskeleton and being moved by protein motors (dynein).

57
Q

What is ‘Division of Labour’?

A

Each organelle in a cell has a specific role within the cell.

58
Q

What is an example of ‘Division of Labour’?

A

Protein synthesis.

59
Q

What is the role of the nucleus in protein synthesis?

A

Contains protein making instructions (DNA).

60
Q

What is the role of the ribosomes/rRNA in protein synthesis?

A

Read instructions and make chain of amino acids.

61
Q

What is the role of the golgi in protein synthesis?

A

Modifies and packages proteins.

62
Q

What is the role of the vesicles in protein synthesis?

A

Transports proteins to cell surface membrane.

63
Q

What is the role of the cell surface membrane in protein synthesis?

A

Releases proteins.

64
Q

What is tubulin?

A

A globular protein that can polymerise from the cell cytoskeleton.

65
Q

What is tubulin essential for the movement of?

A

Polypeptides through RER, vesicles from RER to golgi, vesicles between cisternae of golgi, secretory vesicles from golgi to cell surface membrane.

66
Q

What is the difference in size between prokaryotic and eukaryotic cells?

A

P = 0.1-5 micrometres in diameter, E = up to 40 micrometres in diameter.

67
Q

What is the difference in DNA storage between prokaryotic and eukaryotic cells?

A

P = Circular in plasmids and free in cytoplasm, E = In nucleus.

68
Q

What is the difference in the endoplasmic reticulum between prokaryotic and eukaryotic cells?

A

P = No ER present, E = ER present.

69
Q

What is the difference in organelles between prokaryotic and eukaryotic cells?

A

P = Very few organelles - none with double membrane, E = Double membrane bound organelles.

70
Q

What is the difference in the cell wall between prokaryotic and eukaryotic cells?

A

P = Cell wall always present (peptidoglycan), E = Cell wall sometimes present (e.g. plants).

71
Q

What is the difference in ribosome diameter between prokaryotic and eukaryotic cells?

A

P = 18-20 nanometres, E = 25-30 nanometres.

72
Q

What are the features of plasmids?

A

Replicated independently of a bacterium’s genophone (bacterial conjugation), can be the cause of antibiotic resistance, commonly used in genetic engineering to make copies of genes or large quantities of proteins or hormones.

73
Q

What are the roles of a membrane?

A

Partially permeable barrier between the cell and the environment, within organelles and between organelles and the cytoplasm, site of chemical reactions, site of cell signalling.

74
Q

What is the fluid mosaic model comprised of?

A

Phospholipid bilayer and intrinsic and extrinsic proteins.

75
Q

What is the phospholipid bilayer comprised of?

A

Hydrophilic heads facing out, hydrophobic heads facing in, cholesterol.

76
Q

What are examples of intrinsic proteins?

A

Channel proteins and carrier proteins.

77
Q

What are examples of extrinsic proteins?

A

Glycolipids and glycoproteins.

78
Q

What is the role of cholesterol in the phospholipid bilayer?

A

To control the fluidity and stability of the plasma membrane.

79
Q

What is the order of components and bonds of a phospholipid from head to tail?

A

Phosphate group, phosphoester bond, glycerol, ester bond, fatty acid.

80
Q

What is a glycoprotein?

A

An extrinsic protein attached to a carbohydrate chain.

81
Q

What is a glycolipid?

A

A lipid attached to a carbohydrate chain.

82
Q

What are the functions of intrinsic proteins?

A

To act as channels and gates to let substances through the cell surface membrane.

83
Q

What are two features of the hydrophilic heads of the phospholipid bilayer?

A

They are polar and water soluble.

84
Q

What are two features of the hydrophobic tails of the phospholipid bilayer?

A

They are nonpolar and water insoluble.

85
Q

What is the role of the phospholipid bilayer?

A

To act as a barrier but let small molecules diffuse across.

86
Q

How fast do small polar and nonpolar molecules diffuse across the phospholipid bilayer?

A

Polar = rapidly, nonpolar = much more slowly.

87
Q

What substances are unlikely to diffuse across a membrane?

A

Large molecules and charged particles.

88
Q

What are the roles of glycoproteins?

A

Have antigens for cell recognition, cell signalling, receptors for hormones, cell adhesion.

89
Q

What are the four main types of proteins present in the cell surface membrane?

A

Channel proteins, carrier proteins, enzymes, receptors.

90
Q

What are the roles of glycolipids?

A

Stability and cell recognition.

91
Q

How does cholesterol perform its function?

A

It binds to hydrophobic tails of phospholipids, packing them more closely together.

92
Q

What is the definition of cell signalling?

A

Communication between cells, a molecule released by one cell attaches to another cell, cell recognition.

93
Q

What are the two ways of a signal molecule acting?

A

A signal molecule enters the cell or the binding of a signal molecule causes a change inside the cell.

94
Q

What are the three domains of membrane-bound receptors?

A

Extracellular domain, transmembrane domain and intracellular domain.

95
Q

How do hormones work?

A

They bind to receptors in the cell membranes and trigger a response in the target cell.

96
Q

What do lipid-based hormones do?

A

Diffuse through the plasma membrane.

97
Q

What do protein-based hormones do?

A

Bind to receptors and trigger secondary messengers.

98
Q

What is glucagon?

A

A hormone released to control blood sugar.

99
Q

Why are membrane receptors the target of many medicinal drugs?

A

They are involved in many diseases.

100
Q

What are agonists?

A

Drugs that bind to receptors and mimic the body’s normal messengers.

101
Q

What are antagonists?

A

Drugs that bind to receptors and block the body’s normal messengers.

102
Q

What is the definition of diffusion?

A

The net movement of particles down a concentration gradient, passive so now energy is involved.

103
Q

What is the rate of diffusion determined by?

A

Size of concentration gradient, thickness of exchange surface, distance between two areas, size of molecules, temperature.

104
Q

How do you calculate the surface area and volume of a sphere?

A

SA = 4πr², V = 4/3πr³.

105
Q

When does simple diffusion occur?

A

If the molecules involved can pass freely through a membrane, they have to be small and uncharged, if not, facilitated diffusion is required.

106
Q

What does facilitated diffusion transfer?

A

Water soluble molecules, charged particles and large molecules (e.g. amino acids or glucose).

107
Q

How do substances diffuse using facilitated diffusion?

A

They move down a concentration gradient through carrier proteins or channel proteins (passive like simple diffusion).

108
Q

How do carrier proteins work?

A

Molecules attach, carrier changes shape, releases molecules on other side.

109
Q

How do channel proteins work?

A

Form pores in the membrane, charged particles move down a concentration gradient, only open in response to presence of a molecule.

110
Q

What is the definition of osmosis?

A

The net movement of water across a partially permeable membrane down a water potential gradient (less negative to more negative.

111
Q

What is the unit of water potential?

A

kPa (kilopascals).

112
Q

What is the definition of water potential?

A

The tendency of water molecules in a system to move.

113
Q

What is the water potential of pure water?

A

0 kPa (the highest possible water potential).

114
Q

What happens to a cell in a hypertonic environment in plants?

A

More water moves outside the cell than into the cell so it will become plasmolyzed.

115
Q

What happens to a cell in an isotonic environment in plants?

A

The same volume of water outside the cell is the same as in the cell so it is flaccid.

116
Q

What happens to a cell in a hypotonic environment in plants?

A

Less water moves outside the cell than into the cell so it will become turgid.

117
Q

What happens to a cell in a hypertonic environment in animals?

A

Cells have higher water potential than solution, net movement of water out, shrivelled cells (crenation).

118
Q

What happens to a cell in an isotonic environment in animals?

A

Water potential equal between cells and solution, no net movement water, normal cells.

119
Q

What happens to a cell in a hypotonic environment in animals?

A

Cells have lower water potential than solution, net movement of water in, cells swell, may burst (lysis).

120
Q

What is the definition of active transport?

A

Carrier proteins moving molecules across a membrane against the concentration gradient, which requires energy (not passive).

121
Q

What are examples of active transport?

A

Uptake of glucose and amino acids in the small intestine, the absorption of mineral ions by root hair cells, hydrogen ions uptake by companion cells, exchange of sodium and potassium ions in neurons and muscle cells.

122
Q

What is the process pf active transport?

A

Molecule attaches to carrier protein, ATP molecule provides energy to go against gradient, carrier changes shape and molecule is released on the other side.

123
Q

What do cells carrying out active transport need?

A

Lots of mitochondria to produce enough ATP.

124
Q

What is bulk transport?

A

Used to move extremely large substances across a cell membrane, the two types are exocytosis and endocytosis.

125
Q

What is the definition of exocytosis?

A

The bulk transport of material out of the cell.

126
Q

What is the definition of endocytosis?

A

The bulk transport of material into the cell.

Biology (2 decks)

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