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Biology > UNIT 2 > Flashcards

UNIT 2 Flashcards

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1
Q

Cell membrane
structure

A

•Phospholipid bilayer with embedded intrinsic & extrinsic proteins

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2
Q

Cell membrane
function

A

•Selectively permeable barrier

•controls passage of substances
in and out the cell

•barrier between internal and
external cell environments

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3
Q

Nucleus
Structure

A

•Nuclear pores
• nucleolus
• DNA
• nuclear envelope

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4
Q

Nucleus
Function (4)

A

•Site of transcription & pre- mRNA splicing - mRNA production

•site of DNA replication

•nucleolus makes ribosomes

•nuclear pore allows movement of substances to/from cytoplasm

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5
Q

Mitochondria
Structure

A

•Double membrane with inner membrane folded into cristae

•70S ribosomes in matrix

•small, circular DNA

•enzymes in matrix

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6
Q

Mitochondria
Function

A

•Site of aerobic respiration

•produces ATP

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7
Q

Chloroplast
structure

A

•Thylakoid membranes stacked to form grana, linked by lamellae

•stroma contains enzymes

•contains starch granules, small circular DNA and 70S ribosomes

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8
Q

Chloroplast
function

A

•Chlorophyll absorbs light for photosynthesis to produce organic molecules (glucose)

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9
Q

Organisms
containing
chloroplasts

A

•Plants
•Algae

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10
Q

Golgi apparatus
stucture

A

•Fluid-filled, membrane-bound sacs (horseshoe shaped)

•vesicles at edge

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11
Q

Golgi apparatus
function

A

•Modifies proteins received from RER

•packages them into vesicles to transport to cell membrane for exocytosis

•makes lysosomes

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12
Q

Lysosome
structure

A

•Type of Golgi vesicle containing digestive enzymes

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13
Q

Lysosome
function

A

•Contains digestive enzymes

•e.g lysozymes to hydrolyse pathogens/cell waste products

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14
Q

Rough
endoplasmic
reticulum function

A

•Site of protein synthesis

•folds polypeptides to secondary & tertiary structures

•packaging into vesicles to transport to Golgi

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15
Q

Smooth
endoplasmic
reticulum function

A

•Synthesises and processes lipids

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16
Q

Cell wall
function

A

•Provides structural strength, rigidity and support to cell

•helps resist osmotic pressures

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17
Q

Ribosome
structure

A

•Small and large subunit

•made of protein and rRNA

•free floating in cytoplasm & bound to RER

•70S in prokaryotes, mitochondria and chloroplasts

•80S in eukaryotes

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18
Q

Ribosome
function

A

•Site of translation in protein synthesis

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19
Q

Rough
endoplasmic
reticulum structure

A

•System of membranes with bound ribosomes

•continuous with nucleus

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20
Q

Smooth
endoplasmic
reticulum structure

A

•System of membranes with no bound ribosomes

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21
Q

Cell wall
structure

A

•In plant, fungal and bacterial cells

•plants - made of microfibrils of cellulose

•fungi - made of chitin

•bacteria - murein

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22
Q

Cell vacuole
structure

A

•Fluid-filled

•surrounded by a single membrane called a tonoplast

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23
Q

Contrast
prokaryotic &
eukaryotic cells

A

•Prokaryotic cells are smaller

•prokaryotes have no membrane bound organelles

•prokaryotes have smaller 70S ribosomes

•prokaryotes have no nucleus - circular DNA not associated with histones

•prokaryotic cell wall made of murein instead of cellulose/chitin

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24
Q

Occasional
features of
prokaryotes

A

•Plasmids - loops of DNA

•capsule surrounding cell wall - helps agglutination + adds
protection

•flagella for movement

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25
Q

Cell vacuole
function

A

•Makes cells turgid - structural support

•temporary store of sugars, amino acids

•coloured pigments attract pollinators

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26
Q

Protein
carriers

A

•Bind with a molecule, e.g. glucose, which causes a change in the shape of the protein

•this change in shape enables the molecule to be released to the other side of the membrane

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27
Q

Protein
channels

A

•Tubes filled with water enabling water-soluble ions to pass through the membrane

•selective

•channel proteins only open in the presence of certain ions when they bind to the protein

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28
Q

Features of
viruses

A

•Non living and acellular

•contain genetic material, capsid and attachment proteins

•some (HIV) contain a lipid envelope + enzymes (reverse
transcriptase)

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29
Q

3 types of
microscopes

A

•Optical (light) microscopes

•Scanning electron microscopes (SEM)

•Transmission electron microscopes (TEM)

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30
Q

Magnification

A

•How many times larger the image is compared to the object

•calculated by equation:

•Magnification = image/actual (MIA)

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31
Q

Resolution

A

•The minimum distance between two objects in which they can still be viewed as separate

• determined by wavelength of light (for optical microscopes) or electrons (for electron microcopes)

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32
Q

Optical
microscopes

A

•Beam of light used to create image

• glass lens used for focusing

• 2D coloured image produced

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33
Q

Evaluate
optical
microscopes

A

• Poorer resolution as long wavelength of light - small organelles not visible

• lower magnification

• can view living samples

• simple staining method

• vaccum not required

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34
Q

Transmission
electron
microscopes

A

•Beam of electrons passes through the sample used to create an image

• focused using electromagnets

• 2D, black & white image produced

• can see internal ultrastructure of cell

• structures absorb electrons and appear dark

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35
Q

Evaluation
TEMs

A

•Highest resolving power

• high magnification

• extremely thin specimens required

• complex staining method

• specimen must be dead

• vaccum required

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36
Q

Scanning
electron
microscopes

A

•Beam of electrons pass across sample used to create image

• focused using electromagnets

• 3D, black and white image produced

• electrons scattered across specimen producing image

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37
Q

Evaluation
SEMs

A

•High resolving power

• high magnification

• thick specimens usable

• complex staining method

• specimen must be dead

• vaccum required

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38
Q

Why calibrate
eyepiece
graticule?

A

•Calibration of the eyepiece is required each time the objective lens is changed

• calibrate to work out the distance between each division at that magnification

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39
Q

Purpose of cell
fractionation

A

•Break open cells & remove cell debris

• so organelles can be studied

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40
Q

Homogenisation

A

•Process by which cells are broken open so organelles are free to be separated

• done using homogeniser (blender)

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41
Q

Homogenisation
conditions

A

•Cold reduces enzyme activity preventing organelle digestion

• Isotonic prevents movement of water by osmosis - no bursting / shrivelling of organelles

• Buffered resists pH changes preventing organelle + enzyme damage

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42
Q

Ultra-
centrifugation

A

•Homogenate solution filtered to remove cell debris •solution placed in a centrifuge which spins at a low speed initially

• then increasingly faster speeds to separate organelles according to their density

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43
Q

Differential
centrifugation

A

• Supernatant first out (spun at lowest speed) is most dense = nuclei

• spun at higher speeds

• chloroplasts -> mitochondria -> lysosomes -> RER/SER -> ribosomes (least dense)

44
Q

Binary Fission

A

•Involves circular DNA & plasmids replicating

• cytokinesis creates two daughter nuclei

• each daughter cell has one copy of circular DNA and a variable number of plasmids

45
Q

Cell cycle

A

1) Interphase (G1, S, G2)

2) nuclear division - mitosis or meiosis

3) cytokinesis

46
Q

Interphase

A

•Longest stage in the cell cycle

• when DNA replicates (S-phase) and organelles duplicate

•while cell grows (G1&G2-phase)

• DNA replicates and appears as two sister chromatids held by centromere

47
Q

Mitosis

A

•One round of cell division

• two diploid, genetically identical daughter cells

• growth and repair (e.g. clonal expansion)

• comprised of prophase, metaphase, anaphase and telophase

48
Q

Prophase

A

•Chromosomes condense and become visible

• nuclear envelope disintegrates

• in animals - centrioles separate & spindle fibre structure forms

49
Q

Metaphase

A

•Chromosomes align along equator of cell

• spindle fibres released from poles now attach to centromere and chromatid

50
Q

Anaphase

A

•Spindle fibre contracts (using ATP) to pull chromatids, centromere first, towards opposite poles of cell

• centromere divides in two

51
Q

Telophase

A

•Chromosomes at each pole become longer and thinner again

• spindle fibres disintegrate + nucleus reforms

52
Q

Mitotic index

A

•Used to determine proportion of cells undergoing mitosis

• Calculated as a percentage OR decimal

• Mitotic Index = number of cells undergoing mitosis/total number of cells

• x100 for percentage

53
Q

Fluid mosaic
model

A

•Describes the lateral movement of membranes

• with scattered embedded intrinsic and extrinsic proteins •membrane contains glycoproteins, glycolipids, phospholipids and cholesterol

54
Q

Phospholipids
in membranes

A

•Phospholipids align as a bilayer

• hydrophilic heads are attracted to water

• hydrophobic tails repelled by water

55
Q

Cholesterol

A

• Present in eukaryotic organisms to restrict lateral movement of the membranes

• adds rigidity to membrane- resistant to high temperatures & prevents water + dissolved ions leaking out

56
Q

Selectively
permeable
membrane

A

•Molecules must have specific properties to pass through plasma membrane
•lipid soluble (hormones e.g. oestrogen)
•very small molecules
•non-polar molecules (oxygen)

57
Q

Simple
diffusion

A

•Net movement of molecules from an area of higher concentration to an area of lower concentration

• until equilibrium is reached

• passive

58
Q

Facilitated
diffusion

A

•Passive process using protein channels/carriers

• down the concentration gradient

• used for ions and polar molecules e.e sodium ions

• and large molecules e.g. glucose

59
Q

Osmosis

A

•Net movement of water

• from an area of higher water potential to an area of lower (more negative) water potential

• across a partially permeable membrane

60
Q

Water
potential

A

•The pressure created by water molecules

• measured in kPa and represented by symbol ψ

• pure water has a water potential of 0kPa

• the more negative the water potential, the more solute must be dissolved

61
Q

HypERtonic
solution

A

•When the water potential of a solution is more negative than the cell

• water moves out of the cell by osmosis

• both animal and plant cells will shrink and shrivel

62
Q

HypOtonic
solution

A

•When the water potential of a solution is more positive (closer to zero) than the cell

• water moves into the cell by osmosis

• animal cells will lyse (burst)

• plant cells will become turgid

63
Q

Isotonic

A

•When the water potential of the surrounding solution is the same as the water potential inside the cell

• no net movement in water

• cells would remain the same mass

64
Q

Active
transport

A

•The movement of ions and molecules from an area of lower concentration to an area of higher concentration using ATP and carrier proteins

• carrier proteins act as selective pumps to move substances

65
Q

Role of carrier
protein in active
transport

A

•When molecules bind to the receptor - ATP will bind to protein on inside of membrane and is hydrolysed to ATP / Pi

• protein changes shape and opens inside membrane

66
Q

Co-transport

A

•The movement of two substances across a membrane together, when one is unable to cross the membrane itself

• involves a cotransport protein

• involves active transport

• e.g. absorption of glucose/amino acids from lumen of intestines

67
Q

Molecules
lymphocytes
identify

A

•Pathogens (bacteria, fungi, viruses)

• cells from other organisms of same species (transplants)

• abnormal body cells (tumour cells)

• toxins (released from bacteria)

68
Q

Antigens

A

•Proteins on the cell-surface membrane

• trigger an immune response when detected by lymphocytes

69
Q

Antigenic
variability

A

•When pathogenic DNA mutates causing a change in shape of antigen

• previous immunity is no longer effective as memory cells don’t recognise new shape of antigen.

• specific antibody no longer binds to new antigen

70
Q

Physical
barriers

A

•Anatomical barriers to
• pathogens
• skin
• stomach acid
• lysozymes in tears

71
Q

Phagocytes

A

•Non-specific immune response

• phagocytes become antigen- presenting cells after destroying pathogen

72
Q

T lymphocytes

A

•Made in bone marrow and mature in thymus gland

•involved in cell-mediated immune response

•respond to antigen-presenting cells

73
Q

Antigen-
presenting
cells

A

•Any cell that presents a non-self antigen on their surface
•infected body cells
•macrophage after phagocytosis
•cells of transplanted organ
•cancer cells

74
Q

Role of T
helper cells

A

•Have receptors on their surface that attach to antigens on APCs

•become activated - clonal selection

75
Q

Role of cloned
T helper cells

A

•Some remain as helper T cells & activate B lymphocytes

•stimulate macrophages for phagocytosis

•become memory cells for that shaped antigen

•become cytotoxic killer T cells

76
Q

Cytotoxic
T cells

A

•Destroy abnormal / infected cells by releasing perforin

•so that any substances can enter or leave the cell and this causes cell death

77
Q

B lymphocytes

A

•Made in bone marrow and mature in bone marrow

•involved in humoral immune response

•involves antibodies

78
Q

Humoral
response

A

•APC activates B cell

•B cell undergoes clonal selection and expansion - rapid division by mitosis.

•differentiate into plasma cells / memory B cells

•plasma cells make antibodies

79
Q

B memory cells

A

•derived from B lymphocytes

•remember specific antibody for particular antigen

•will rapidly divide by mitosis and differentiate in plasma cells upon secondary encounter

•resulting in large numbers of antibodies rapidly

80
Q

Antibodies

A

•Quaternary structure proteins made of four polypeptide chains

•different shaped binding site = variable region

•complementary to a specific antigen

81
Q

Antibody
structure

A

• Y shape

82
Q

Agglutination

A

•Antibodies have two binding sites and are flexible - clumps pathogens together

•makes it easier for phagocytes to locate and destroy pathogen

83
Q

Passive
immunity

A

•Antibodies introduced into body

•plasma and memory cells not made as no interaction with antigen

•short-term immunity

•fast acting

84
Q

Active
immunity

A

•Immunity created by own immune system - antibodies made

•exposure to antigen

•plasma and memory cells made

•long term immunity

•slower acting

85
Q

Natural active
immunity

A

•After direct contact with pathogen through infection

•body creates antibodies and memory cells

86
Q

Artificial active
immunity

A

•Creation of antibodies and memory cells following introduction of an attenuated pathogen or antigens

•vaccination

87
Q

Vaccinations

A

• Small amounts of dead or attenuated pathogens injected / ingested

•humoral response activated

•memory cells are able to divide rapidly into plasma cells when re-infected

88
Q

Primary vs
Secondary
response

A

•Primary = first exposure to the pathogen

•longer time for plasma cell secretion & memory cell production

•for the secondary response, memory cells divide rapidly into plasma cells

•so a large number of antibodies made rapidly upon reinfection

89
Q

Herd
immunity

A

•When enough of the population is vaccinated so pathogen is not transmitted and spread easily

•provides protection for those without vaccine

90
Q

Monoclonal
antibodies

A

•A single type of antibody that can be isolated and cloned

•antibodies that are identical - from one type of B lymphocyte

•complementary to only one antigen

91
Q

Uses of
monoclonal
antibodies

A

•Medical treatment - targeting drugs by attaching antibody complementary to tumour cell antigen

•medical diagnosis - pregnancy tests

92
Q

Pregnancy test

A

•ELISA test which uses 3 monoclonal antibodies and enzymes to test for hCG

93
Q

Purpose of
ELISA test

A

•Detect the presence and quantity of an antigen

•used for medical diagnosis. Eg., HIV

94
Q

Ethical issues
with monoclonal
antibodies

A

•Requires mice to produce antibodies and tumour cells

•requires a full cost-benefit analysis

95
Q

HIV structure

A

•Core = RNA and reverse transcriptase

•capsid = protein coat

•lipid envelope taken from hosts cell membrane

•attachment proteins so it can attach to Helper T cells

96
Q

HIV replication

A

•Attaches to CD4 receptor on helper T cells

•protein fuses with membrane allowing RNA + enzymes to enter

•reverse transcriptase makes DNA copy and this is inserted into nucleus

•nucleus synthesises viral proteins

97
Q

Auto
Immunodeficiency
Syndrome (AIDs)

A

•When HIV has destroyed too many T helper cells, host is unable to produce adequate immune response to other pathogens

•host susceptible to opportunistic infections

98
Q

Role of
antibodies in
ELISA

A

•First antibody added is complementary to antigen in well - attaches

•second antibody with enzyme added which attaches to first antibody as complementary.

•when substrate solution added enzyme can produce colour change

99
Q

Why vaccines
may be unsafe

A

•Inactive virus may become active - viral transformation

•non-pathogenic virus can mutate and harm cells

•side effects of immune response

•people may test positive for disease

100
Q

Why are
antibiotics
ineffective against
viruses?

A

• Viruses are inside host cells where antibiotics cannot reach

•antibiotics affect parts of bacteria that viruses do not have (e.g the cell wall)

101
Q

Why do you
wash well in
ELISA

A

•Removes unbound 2nd antibodies

•otherwise enzyme may be present → colour change → false positive

102
Q

Pathogens

A

•Microorganisms that cause a disease

•by releasing toxins or killing cells / tissues

103
Q

Cytokinesis

A

•Final stage in the cell cycle

•when the cytoplasm splits in two

•creates two new cells

104
Q

Uncontrolled
mitosis

A

•Uncontrolled cell division can lead to the formation of tumours and of cancers

•many cancer treatments are directed at controlling the rate of cell division

105
Q

Viral
replication

A

•Following injection of their nucleic acid

•the infected host cell replicates the virus particles

106
Q

Cell adaptations for
rapid transport
across membranes?

A

•Increase in surface area or membrane

•increase in the number of protein channels and carrier molecules in the membranes

107
Q

Antigen-
antibody
complex

A

•When a complementary antibody binds to an antigen

•this clumps pathogens together (agglutination)

Biology (3 decks)

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