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AQA A level Biology > Cells > Flashcards

Cells Flashcards

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1
Q

The structure of eukaryotic cells

A

Cell-surface membrane.
Nucleus (containing chromosomes, consisting of protein-bound,
linear DNA, and one or more nucleoli)
mitochondria.
Chloroplasts (in plants and algae).
Golgi apparatus and Golgi vesicles
lysosomes (a membrane-bound organelle that releases hydrolytic enzymes). Ribosomes.
Rough endoplasmic reticulum and smooth endoplasmic reticulum.
Cell wall (in plants, algae and fungi).
Cell vacuole (in plants).

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2
Q

Organisation of specialised cells

A

Cells into tissues, tissues into organs and organs into systems.

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3
Q

The structure of prokaryotic cells

A

Cytoplasm that lacks membrane-bound organelles.
Smaller ribosomes.
Single circular DNA molecule that is free in the cytoplasm and is not associated with proteins.
Cell wall that contains murein, a glycoprotein.
One or more plasmids.
A capsule surrounding the cell.
One or more flagella.

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4
Q

The structure of viruses

A

Genetic material, capsid and attachment protein.

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5
Q

Magnification

A

How many times bigger the image is in comparison to real object size

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6
Q

Resolution

A

The ability to distinguish between two objects

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7
Q

Definition of diffusion

A

The net movement of molecules or ions from a region of high concentration to a region of low concentration

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8
Q

What is facilitated diffusion?

A

Diffusion which transports large and polar molecules across membrane, facilitated by transmembrane channel and carrier proteins.

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9
Q

What is osmosis?

A

Movement of water molecules from a region of higher water potential (less negative) to a region of lower water potential (more negative) across a partially permeable membrane

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10
Q

What is active transport?

A

Movement of molecules or ions across the membrane against the concentration gradient from a lower region of concentration to a higher concentration, requiring ATP

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11
Q

Definition of antigen

A

Part of organism which is recognised as foreign by immune system, often embedded in cell surface membrane or cell of invading cells.

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12
Q

Definition of antibody

A

Proteins which form a vital part of bodys defense system. Produced by B lymphocytes by the presence of an complementary antigen.

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13
Q

Antibody structure

A

Made up of four polypeptide chains
Two variable regions
Two constant regions

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14
Q

Ethical issues of monoclonal antibodies

A
  • Animal testing
  • Animal based substances
    -Testing on humans potentially putting them at risk
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15
Q

Role of helper T cells

A

Stimulates cytotoxic T cells (Tc cells), B cells and phagocytes

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16
Q

Importance of vaccines

A

To provide protection for individuals and populations against disease by stimulating immune system to produce specific antibodies and memory cells to ensure efficient destruction of pathogen if it ever entered body.

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17
Q

Virus cell division

A

Being non-living, viruses do not undergo cell division. Following injection of their nucleic acid, the infected host cell replicates the virus particles.

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18
Q

Mitosis

A

Cell division resulting in two genetically identical daughter cells

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19
Q

Formation of tumours and cancers

A

Uncontrollable cell division

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20
Q

Controlled cell division process

A

Mitosis

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21
Q

Cell fractionation

A

The process where cells are broken up and the different organelles they contain are separated out

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22
Q

Microscopy

A

The process of producing a magnified image of an object using the instruments of microscopes

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23
Q

Solution for cell fractionation properties

A

Ice cold- reduce enzyme activity which may break down organelles
Buffered- prevents change in pH affecting organelles
Isotonic- prevent having an osmotic effect

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24
Q

Stages of cell fractionation

A

Homogenation
- breaking up of cells in homogeniser, resultant fluid (homogenate) filtered to remove large debris
Ultracentrifugation
- separation of fragments in homogenate in a centrifuge machine

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25
Q

Limits to optical microscope

A

The resolution would be low as light has a long wavelength

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25
Q

Process of ultracentrifugation

A
  • Filtrate placed in centrifuge and spun at lowest speed, heaviest organelles (nuclei) forced to bottom of tube forming a pellet
  • Supernatant removed and transferred to another tube and spun in centrifuge at a faster speed forcing down next heaviest organelles
  • Process continues till desired organelle is separated
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25
Q

Advantages of electron microscope invention in the 1930s

A
  • Short wavelength for electron beam so high resolution
  • Electrons are negatively charged so beam can be focused using electromagnets
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26
Q

Two types of elctron microscope

A

Transmission Electron Microscope
Scanning Electron Microscope

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27
Q

TEM

A

Use electromagnets to focus a beam of electrons which are transmitted through specimen

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28
Q

Advantages of TEM

A

-High resolution images
- Show internal structures of organelles

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28
Q

LImitations of TEM

A
  • Extremely thin specimen needed for electrons to pass
  • Dead specimen as process happens in a vacuum
  • 2D images
29
Q

SEM

A

Scan a beam of electrons across surface of specimen, knocking electrons gathered on cathode ray to form image

30
Q

Cell specialisation

A

In multicellular organisms, cells become specialised for specific functions through a process known as differentiation

31
Q

Stages of cell cycle

A

Interphase, Prophase, Metaphase, Anaphase, Telophase (cytokinesis)

32
Q

Importance of mitosis

A

Growth, repair, reproduction

33
Q

Treatment of cancer

A

Chemical drugs (chemotherapy) used to disrupt cell cycle
- preventing DNA replication
- Inhibiting metaphase by interfering with spindle
Radiotherapy
- Damage DNA in cancer cell

34
Q

What is simple diffusion?

A

Movement of small and non polar molecules to a lower region of concentration, particles randomly in motion due to kinetic energy

35
Q

Structure of HIV

A

Lipid envelope (derived from the cell membrane of the host helper T cell) with attachment proteins embedded in.
Capsid protein coat.
Core which holds genetic material.
Proteins (including the enzyme reverse transcriptase).

36
Q

Replication of viruses

A

Virus uses attachment protein to bind to complementary receptors on host cell’s plasma membrane. Genetic material released into cells. Reverse transcriptease takes place. Viral particles will be produced and cause host cell to burst through a lyctic release where virus moves to new cells and tisues.

37
Q

HIV formation into AIDS

A

When an HIV virus infects a helper T cell and replicates, the cells are killed.
As HIV spreads through the body and more helper T cells are killed, the immune system weakens.
The weak immune system makes the individual highly susceptible to infection by other pathogens. This is AIDs.

38
Q

HIV full name

A

Human Immunodefiency Virus

39
Q

AIDS full name

A

Acquired Immunodeficiency Syndrome

40
Q

What does ELISA stand for?

A

Enzyme Linked Immunosorbant Assay

41
Q

What are channel proteins?

A

Allow specific charged particles to pass across membrane.

42
Q

What are carrier proteins?

A

They bind to specific molecule and change their shape allowing molecule to enter cell, protein would then return to shape.

43
Q

Isotonic

A

Equal water potential either side of membrane

44
Q

Hypotonic

A

Solution has higher water potential than inside of cell
Animal cell- cell swells and cytosis occurs
Plant cell- cell swells and gets turgid

45
Q

Hypertonic

A

Inside of cell has higher water potential than solution
Animal cell- cell shrivels and shrinks
Plant cell- cell shrinks and is plasmolysed

46
Q

Water potential of pure water

A

0

47
Q

What is a vaccine?

A

The introduction to the body a dead or attenuated pathogen which brings about an immune response preventing an individual contracting a disease.

48
Q

Ways a vaccination is taken

A

May be injected or taken orally

49
Q

Ethical issues of vaccinations

A

-Animal testing
-Animal based substances used
-Testing on humans potentially putting them at risk
-Benefits must outweigh financial cost
-People declining vaccine stopping protection of population

50
Q

What is active immunity?

A

Stimulation of the production of antibodies by the individuls own immune system (direct contact with pathogen)

51
Q

Types of active immunity

A

Natural- normal life processes (exposure to disease)
Artificial- medical intervention (vaccine)

52
Q

What is passive immunity?

A

Introduction of anitbodies to individual from an outside source (no direct contact with pathogen)

53
Q

Factors of active immunity

A
  • Requires being exposed to antigen
  • Slow response
  • Memory cells produced
  • Long term production
54
Q

Factors of passive immunity

A
  • No exposure to antigen required
  • Immediate response
  • No memory cells produced
  • Short term protection
55
Q

Meaning of herd immunity

A

When a large proportion of a population has been vaccinated making it difficult for a pathogen to spread - advantageous to those who havent got vaccine as it protects them not catching disease.

56
Q

Reasons a vaccine may not eliminate a disease

A
  • Individuals not getting vaccine for religious, medical or ethical reasons
  • Multiple varieties of pathogen
  • Antigenic variation as pathogen frequently mutates causing vaccine to be ineffective
  • Individuals getting disease before or after vaccine as immunity levels arent high enough to prevent it
  • Pathogens may ‘hide’ from immune system in cells or intestines
57
Q

Side effects of cancer treatment

A

May disrupt cell cycle of normal cells as it cannot distinguish between the two
( more likely kill tumour cells as they have a much faster division rate)

58
Q

Role of B cells

A

Create and secrete antibodies complementary to antigen.
Divide by mitosis to form plasma cells.
Produce memory cells for further antigen intrusion

59
Q

Advantages of SEM

A
  • Produce 3D images
  • Can be used for thicker specimens as electrons dont pass through
  • Can see surface of specimen
60
Q

Limitations of SEM

A
  • Low resolution images
  • No living specimens used as prepared in a vacuum
61
Q

What is added to microscope images to produce colour?

A

False colour imaging

62
Q

Which polymer are antigens typically?

A

Typically proteins so are enourmously variable due to tertiary structure.

62
Q

Blood groups recognition

A

A- a antigens
B- b antigens
AB- a and b antigens
o- neither antigens

63
Q

How may you treat HIV?

A

Treating HIV is difficult because it is a virus.
HIV has some virus-specific enzymes (e.g. reverse transcriptase) and so antiviral drugs can be designed to target the reverse transcriptase enzyme

64
Q

Binary fission

A

DNA replication
Cell growth
Cell division

65
Q

What is binary fission

A

Type of asexual reproduction in prokaryotes

66
Q

Temporary mounts

A
  • Add a drop of water onto slide to keep specimen in place
  • Place a thin specimen on water
  • Add a drop of specific stain (highlight certain objects).
  • Slowly add a cover slip, place upright next to slide and tilt it down onto specimen using a mounted needle to prevent artefacts
67
Q

What are artefacts?

A

Things present on microscope which are not present on cell or specimen
- Air bubbles, fingertips, damage to specimen
(typically formed during prep)

68
Q

Two types of elisa tests?

A

Direct- uses a single antibody complementary to antigen being tested for
Indirect- uses two different antibodies (primary and secondary)

69
Q

Function of elisa tests

A
  • uses antibodies to detect presence of proteins in a sample, as well as its quantity.
70
Q

Lateral flow tests function

A

Used to detect the presence of hormones or antigens from a patient’s sample.

71
Q

Cell surface membrane / plasma membrane

A
72
Q
A

AQA A level Biology (6 decks)

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