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Biology > 2) Cells > Flashcards

2) Cells Flashcards

- Cell structure - Transport across cell membranes - Cell recognition and the immune system

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1
Q

what property of light limits the resolution of a light microscope?

A

light’s long wavelength

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2
Q

state the magnification equation

A

magnification = image size/object size

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3
Q

what is the definition of resolution?

A

the minimum distance apart that two objects can be distinguished as separate objects in an image

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4
Q

what are the two types of electron microscope?

A

transmission electron microscope (TEM)
scanning electron microscope (SEM)

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5
Q

how is the beam of electrons focused in an electron microscope?

A

by electromagnets

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6
Q

why do electron microscopes need to be in a vacuum?

A

so that the particles in air do not deflect the electrons out of the beam alignment

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7
Q

describe how a TEM works

A

A beam of electrons passes through a thin section of a specimen.
Areas that absorb the electrons appear darker on the electron micrograph produced.

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8
Q

describe how a SEM works

A

Beam of electrons passes across the surface of a specimen and scatters
The pattern of scattering builds a 3D image depending on the contours.

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9
Q

what are the main limitations of TEMs

A

system must be in a vacuum - specimen cannot be living
black and white image
specimen must be very thin for electrons to pass through

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10
Q

what are the main limitations of SEMs?

A

system must be in a vacuum - specimen cannot be living
black and white image
lower resolution than TEM

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11
Q

what is cell fractionation?

A

the process in which different parts and organelles of a cell are separated to be studies

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12
Q

what are the three main steps of cell fractionation?

A

homogenisation
filtration
ultracentrifugation

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13
Q

how can homogenisation be done?

A

grinding cells using a pestle and mortar, or in a blender

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14
Q

what is the purpose of homogenisation?

A

to break up the plasma membrane and release the organelles

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15
Q

describe the solution that the cells are homogenised in

A

ice-cold, isotonic, buffered

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16
Q

why must the solution be ice-cold?

A

to reduce enzyme activity that could break down the organelles

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17
Q

why must the solution be isotonic?

A

to prevent damage to the organelles through osmosis

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18
Q

why must the solution be pH buffered?

A

to prevent pH fluctuations

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19
Q

why is the solution filtered before ultracentrifugation?

A

to remove large debris

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20
Q

describe the process of ultracentrifugation

A
  1. homogenate (homogenised organelle solution) is spun at a low speed in a centrifuge
  2. heaviest organelles, the nuclei, are forced to the bottom forming a pellet
  3. fluid is removed leaving the nuclei pellet
  4. supernatant is spun again faster forming the next heaviest pellet - mitochondria
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21
Q

what are the defining features of a eukaryotic cell?

A

contain a nucleus and membrane bound organelles

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22
Q

describe the structure of the nucleus

A

Double membrane called the nuclear envelope containing nuclear pores.
Contains chromatin and a nucleolus.
Granular jelly like material called nucleoplasm makes up the bulk.

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23
Q

what is the purpose of the nuclear pores?

A

enable molecules to enter and leave the nucleus

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24
Q

what is the purpose of the nucleolus?

A

site of ribosome production

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25
Q

what is the substance that makes up the bulk of the nucleus?

A

nucleoplasm

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26
Q

what is the role of the RER?

A

folds and processes proteins made on the ribosomes

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27
Q

what is the role of the SER?

A

produces and processes lipids

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28
Q

what is the role of the golgi body?

A

processes and packages proteins and lipids
produces lysosomes

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29
Q

describe the structure of the mitochondria

A

oval shaped organelle bound by a double membrane
inner membrane folded to form cristae with matrix on the inside

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29
Q

what is the role of centrioles?

A

involved in producing spindle fibres for cell division

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30
Q

what is the role of ribosomes?

A

protein synthesis

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31
Q

what is role of lysosomes?

A

contain digestive enzymes so can digest molecules

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32
Q

what are prokaryotic cell walls made from?

A

murein (peptidoglycan)

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33
Q

what is the purpose of a prokaryotic cell’s capsule?

A

helps the cell retain moisture and adhere to surfaces

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34
Q

what is a plasmid?

A

circular ring of DNA

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35
Q

what is the role of a prokaryotic cell’s flagellum?

A

rotates to move the cell

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36
Q

what is the purpose of pili in a prokaryotic cell?

A

allow them to attach to other bacterial cells

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37
Q

what is the role of ribosomes in prokaryotic cells?

A

protein synthesis

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38
Q

what are mesosomes in prokayote?

A

infoldings of the inner membrane, containing enzymes for respiration

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39
Q

describe the structure of a virus

A

nucleic acid (either DNA or RNA) enclosed in a protein coat called the capsid, sometimes covered by a lipid layer called the envelope

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40
Q

what is the role of mitosis and the cell cycle?

A

to produce identical daughter cells for growth and asexual reproduction

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41
Q

what are the three stages of the cell cycle?

A

mitosis
interphase
cytokinesis

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42
Q

what are the four stages of mitosis?

A

prophase
metaphase
anaphase
telophase

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43
Q

what happens during interphase?

A

the cell grows and prepares to divide
chromosomes and some organelles are replicated
chromosomes begin to condense

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44
Q

what happens during cytokinesis?

A

the parent and replicated organelles move to opposite sides of the cell and the cytoplasm divides producing 2 daughter cells

45
Q

mitosis is needed for what three reasons?

A

growth
repair
production

46
Q

how is mitosis important for growth?

A

cells produced are identical so organisms can grow using mitosis

47
Q

how is mitosis important for repair?

A

all cells produced are identical so organisms can replace dead tissues using mitosis

48
Q

how is mitosis important for reproduction?

A

some single-celled organisms reproduce by dividing into two identical daughter cells by mitosis

49
Q

what happens in prophase?

A

Chromosomes condense
Centrioles move to opposite ends of the cell, forming spindle fibres
Nuclear envelope breaks down and chromosomes are free in cytoplasm

50
Q

what happens in metaphase?

A

Chromosomes line up along middle of the cell and become attached to the spindle by their centromere

51
Q

what happens in anaphase?

A

Sister chromatids separate.
Chromatids are pulled to opposite poles of the spindle

52
Q

what happens in telophase?

A

Chromatids decondense.
A nuclear envelope forms around each group of chromosomes so there are 2 nuclei.
Cytokinesis finishes

53
Q

what is the name of the process by which prokaryotic cells divide?

A

binary fission

54
Q

explain the steps of binary fission

A

Circular DNA replicates and attaches to cell membrane.
Plasmids replicate.
Cell membrane grows between the 2 DNA molecules and pinches inward, dividing cytoplasm.
New cell wall forms, dividing the original cell.

55
Q

what genetic information do daughter cells created by binary fission have?

A

a single copy of circular DNA and a variable number of copies of the plasmids

56
Q

why do virus not undergo cell division?

A

because they are non-living

57
Q

how do viruses replicate?

A

inject their nucleic acids into another cell which then replicates the virus particles

58
Q

what is the main function of the membrane?

A

controlling movement of substances in and out of the cell/organelle

59
Q

describe the arrangement of phospholipids in the cell membrane bilayer

A

hydrophilic heads point outward (attracted to water on the outside of the cell)
hydrophobic tails point inwards (repelled by the water)

60
Q

what kinds of molecules can pass through the phospholipid bilayer? what can’t?

A

lipid soluble molecules can pass through but water soluble cannot

61
Q

what properties does the phospholipid bilayer give the cell membrane?

A

it is flexible and self-sealing

62
Q

what is the difference between intrinsic and extrinsic proteins?

A

intrinsic - integrated fully throughout the membrane
extrinsic - on the surface

63
Q

what 4 components are found embedded in the phospholipid bilayer?

A

proteins
cholesterol
glycolipids
glycoproteins

64
Q

are carrier proteins intrinsic or extrinsic?

A

intrinsic

65
Q

what is the purpose of proteins in the cell membrane?

A

aids movement across the membrane
provides mechanical support
act as receptors

66
Q

what is the purpose of cholesterol in the cell membrane?

A

makes the membrane more rigid
reduces lateral movement of phospholipids
prevents water/dissolved ions leaking

67
Q

how does cholesterol in the cell membrane prevent leakage of water and dissolved ions?

A

because it is hydrophobic

68
Q

what are glycolipids?

A

carbohydrate bound to a lipid

69
Q

what is the purpose of glycolipids in a cell membrane?

A

act as cell surface receptors and allow cells to adhere to one another, forming tissues

70
Q

what is a glycoprotein?

A

carbohydrates attached to extrinsic proteins

71
Q

what is the purpose of glycoproteins in a cell membrane?

A

act as cell surface receptors and neurotransmitters
allow cells to adhere to one another, forming tissues

72
Q

what is diffusion?

A

passive movement of small, non-polar molecules down a concentration gradient through the phospholipid bilayer

73
Q

what is facilitated diffusion?

A

movement of large, polar, charged molecules via a channel/carrier protein in the cell membrane down a concentration gradient

74
Q

what is osmosis?

A

diffusion of water molecules down a water potential gradient through a partially permeable membrane

75
Q

what is active transport?

A

movement of molecules through carrier proteins against a concentration gradient, using ATP

76
Q

what is co-transport?

A

where two substances are both transported across a membrane simultaneously either in the same direction or opposite directions via a carrier protein

77
Q

what four factors increase the rate of gas exchange by diffusion?

A
  • increasing surface area of the exchange surface
  • diffusion gradient becomes steeper
  • temperature increases
  • diffusion pathway decreases
78
Q

what are the main differences between bacteria and viruses?

A
  • bacterial are prokaryotic cells whereas viruses consist of nucleic acid in a protein coat
  • bacteria do not require a host to survive, viruses do
  • viruses are smaller than bacteria
  • bacteria have cell wall, cell membrane and cytoplasm as well as organelles, e.g. ribosomes, whereas viruses do not
79
Q

give three examples of physical barriers to infection

A
  • skin (physical barrier consisting of keratin)
  • stomach acid (HCl) (kills bacteria)
  • gut and skin flora (natural beneficial bacteria compete with pathogens for food and space)
80
Q

what allows the immune system to identify cells as self or non-self?

A

antigens on their surface

81
Q

give four examples of non-specific immune responses

A
  • inflammation
  • lysozyme action
  • interferons
  • phagocytosis
82
Q

explain inflammation as a non-specific immune response to infection

A
  • histamine released by damaged tissues increase blood flow to affected area and increase permeability of blood vessels
  • as a result, antibodies, WBCs, and plasma leak out into the infected tissues and destroy the pathogen
83
Q

explain lysozyme action as a non-specific immune response to infection

A

lysozymes found in secretions such as tears and mucus kill bacterial cells by damaging their cell walls

84
Q

explain interferons as a non-specific immune response to infection

A

interferons (protein released by body) prevent viruses spreading to uninfected cells by stopping protein synthesis in viruses

85
Q

what are the two types of immune response?

A

specific and non-specific

85
Q

where are B-cells produced? where do they mature?

A
  • produced in bone marrow
  • mature in bone marrow
86
Q

where are T-cells produced? where do they mature?

A
  • produced in the bone marrow
  • mature in the thymus gland
87
Q

which immune response are B cells involved in?

A

humoral response

88
Q

which immune response are T-cells involved in?

A

cell mediated response

89
Q

what are memory cells?

A

cells which replicate themselves when exposed to a pathogen and remain in the lymph nodes searching for the same antigen, resulting in much faster immune response if the person becomes infected with the same pathogen again

90
Q

what is the role of plasma cells?

A

produce antibodies

90
Q

what is the role of T-helper cells?

A

stimulate B cells and cytotoxic T cells to divide

90
Q

what is the role of cytotoxic T-cells?

A

destroy pathogen-infected cells

90
Q

what is an antigen?

A

protein that is recognised as non-self by the immune system and triggers an immune response

90
Q

what does the presence of an antigen trigger?

A

the production of an antibody

90
Q

what are the 2 kinds of immune response?

A

non-specific and specific

91
Q

how are the effects of a specific immune response different to the effects of a non-specific?

A

specific responses are slower in action at first but can provide long-term immunity

91
Q

where are lymphocytes produced?

A

by stem cells in the bone marrow

91
Q

what are the 2 types of lymphocytes?

A

B-cells and T-cells

92
Q

what has to happen for T-lymphocytes to respond to antigens?

A

antigens must be presented on a body cell

93
Q

what are the four most common antigens?

A
  • Pathogens
  • Abnormal body cells (e.g. cancerous)
  • Toxins
  • cells from other individuals of the same species (e.g. transplanted)
94
Q

Describe the stages of phagocytosis

A
  • phagocyte recognises foreign antigens on a pathogen
  • cytoplasm of the phagocyte engulfs the pathogen
  • pathogen is how contained in a phagosome
  • A lysosome fuses with the phagosome and releases lysozymes that break down the pathogen
  • phagocyte presents the pathogen’s antigens on its surface to activate T- Cells
95
Q

what are the first cells to respond to an immune system trigger?

A

phagocytes

96
Q

where are phagocytes found?

A

in the blood and in tissues

97
Q

what is the role of T- helper cells?

A

release chemical signals that activate phagocytes and cytotoxic T-cells

98
Q

what do T-cells bind to? how?

A

they have receptors on their surface that bind to complementary antigens presented to it by phagocytes

99
Q

what are B-cells covered with?

A

antibodies

100
Q

what is formed when an antibody binds to an antigen?

A

antigen-antibody complex

101
Q

why can each B-cell only bind to one specific antigen?

A

each B-cell has a different specific shaped antibody on its membrane so they can only bind to one specific antigen

102
Q
A

Biology (8 decks)

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