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cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
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
  1. Nuclear envelope: double membrane surrounding nucleus, outer membrane continuous with the (R)ER of the cell.
  2. Nuclear pores: allow the passage of larger molecules, such as mRNA, out of the nucleus.
  3. Nucleoplasm: granular, jelly-like material making up the bulk of the nucleus.
  4. Chromosomes: protein-bound, linear DNA.
  5. Nucleolus: small spherical region(s) in nucleoplasm. Manufactures ribosomal RNA and assembles ribosomes.
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4
Q

Nucleus Function

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
  1. Double membrane surrounding organelle - controls entry and exit of material.
  2. Cristae - extensions of the inner membrane, providing a large surface area for the attachment of enzymes and other proteins during respiration.
  3. Matrix - makes up the remainder - contains proteins, lipids, ribosomes and DNA (allows mitochondria to produce own proteins) and some respiratory enzymes.
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6
Q

Mitochondria Function

A

Site of aerobic respiration produces ATP

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7
Q

Chloroplast structure

A

Found in plants and algae.

  1. Chloroplast envelope - double plasma membrane, highly selective, surrounds the organelle.
  2. Grana - stacks of disc-shaped thylakoid membrane.
  3. Thylakoids - contain chlorophyll used in photosynthesis, can be linked by lamellae to other grana.
  4. Stroma - fluid-filled matrix where Calvin Cycle takes place. Also contains starch grains.
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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
  1. Compact system of flattened sacs and stacked membranes (cisternae).
  2. Vesicles - modified proteins and lipids transported to cell membrane where they fuse with it, and then egest contents to the outside.
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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

Golgi vesicles with proteases, lipase and lysozymes

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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

3D system of sheet-like membranes - continuous with the outer membrane of the nuclear double membrane.

Membrane contains a network of tubules and flattened sacs called cisternae.
RER - ribosomes on the outer surface of the membranes.

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20
Q

Smooth endoplasmic reticulum structure

A

3D system of sheet-like membranes - continuous with the outer membrane of the nuclear double membrane.

Membrane contains a network of tubules and flattened sacs called cisternae.
SER - lacks ribosomes on its surface and is often more tubular in its appearance.

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21
Q

Cell wall structure

A

Found in plants, algae and fungi.

Cellulose microfibrils embedded in a matrix - contribute to overall cell wall strength are considerably strong
Middle lamella - marks the boundary between adjacent cell walls and cements adjacent cells together.

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22
Q

Cell vacuole structure

A
  1. Fluid-filled sac bounded by a single membrane.
  2. Single membrane around it called tonoplast.
  3. Solution of mineral salts, sugars, amino acids, wastes and sometimes pigments such as anthocyanins.
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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
magnification=image size/actual size

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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

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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35
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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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)

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44
Q

Binary Fission

A
  1. Circular DNA molecule replicates, and both copies attach to the cell membrane.
  2. Plasmids also replicate.
  3. Cell membrane begins to grow between the two DNA molecules and begins to pinch inwards - dividing cytoplasm in two.
  4. New cell wall forms between the DNA molecules, dividing the original cell into two identical daughter cells - each with a copy of the circular DNA and a variable number of copies of the plasmids.
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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
mitotic index=no. of cells in mitosis/total no. of cells

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

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

64
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

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

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

75
Q

B lymphocytes

A

Made in bone marrow and mature in bone marrow involved in humoral immune response
involves antibodies

76
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

77
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

78
Q

Antibodies

A

Quaternary structure proteins made of four polypeptide chains different shaped binding site = variable region
complementary to a specific antigen

79
Q

Agglutination

A

Antibodies have two binding sites and are flexible - clumps pathogens together
makes it easier for phagocytes to locate and destroy pathogen

80
Q

Passive immunity

A

Antibodies introduced into body plasma and memory cells not made as no interaction with antigen
short-term immunity fast acting

81
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

82
Q

Natural active immunity

A

After direct contact with pathogen through infection body creates antibodies and memory cells

83
Q

Artificial active immunity

A

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

84
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

85
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

86
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

87
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

88
Q

Uses of monoclonal antibodies

A

Medical treatment - targeting drugs by attaching antibody complementary to tumour cell antigen
medical diagnosis - pregnancy tests

89
Q

Purpose of ELISA test

A

Detect the presence and quantity of an antigen
used for medical diagnosis. Eg., HIV

90
Q

Pregnancy test

A

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

91
Q

Ethical issues with monoclonal antibodies

A

Requires mice to produce antibodies and tumour cells requires a full cost-benefit analysis

92
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

93
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

94
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

95
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

96
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

97
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)

98
Q

Why do you wash well in ELISA

A

Removes unbound 2nd antibodies
otherwise enzyme may be present colour change false positive

99
Q

Pathogens

A

Microorganisms that cause a disease
by releasing toxins or killing cells / tissues

100
Q

Cytokinesis

A

Final stage in the cell cycle when the cytoplasm splits in two
creates two new cells

101
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

102
Q

Viral replication

A

Following injection of their nucleic acid
the infected host cell replicates the virus particles

103
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

104
Q

Antigen- antibody complex

A

When a complementary
antibody binds to an antigen
this clumps pathogens together (agglutination)

105
Q

centromere

A

cellular structure involved in the process of cell division.

106
Q

chromatid

A

Each copy of a particular chromosome

107
Q

G1 phase

A

produces new organelles and causes the cells to grow in size

108
Q

S phase

A

synthesis phase of cell cycle; portion of interphase- DNA is replicated.

109
Q

G2 phase

A

Cell checks for DNA errors + begins- form centrosomes

110
Q

antigen

A

produce B cells-specific to antigen

A-level Biology (8 decks)

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