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AQA AS Biology > cells > Flashcards

cells Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are eukaryotic cells?

A

animal / plant cells.
they contain a nucleus and membrane bound organelles.

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2
Q

structure of eukaryotic cells (what they contain)?

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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3
Q

function of golgi apparatus?

A

processes and packages proteins and lipids.
it also produces lysosomes.

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4
Q

function of smooth endoplasmic recticulum?

A

produces and processes lipids

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5
Q

function of rough endoplasmic recticulum?

A

folds and processes proteins made on the ribosomes.

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6
Q

Specialised cells are organised into…

A

into tissues, tissues into organs and organs into systems.

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7
Q

how do prokaryotic cells differ from eukaryotic cells?

A

Prokaryotic cells are much smaller than eukaryotic cells. They also differ from eukaryotic cells in having:
- cytoplasm that lacks membrane-bound organelles
- smaller ribosomes
- no nucleus; instead they have a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins
- a cell wall that contains murein, a glycoprotein.

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8
Q

viruses are…

A

acellular and non-living.

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9
Q

the structure of viruses include…

A

genetic material, capsid and attachment protein

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10
Q

how does an optical microscope work?

A

Visible light passes and is bent through the lens system to enable the user to see the specimen.

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11
Q

optical microscopes limitations

A
  • specimen can be alive although Individual cells are generally transparent and their components are not distinguishable unless they are coloured with special stains.
    Staining usually kills the cells.
  • Maximum resolution is 0.2 micrometres.
  • only the nucleus and mitochondria can be seen with a light microscope.
  • The maximum magnification is around x1,500.
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12
Q

how do electron microscopes work?

A

-electron microscopes use a beam of electrons which allows higher magnification and higher resolving power.
This means that more detail can be seen.

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13
Q

how does a transmission electron microscope work?

A

In a TEM, the electron beam penetrates the cell and provides details of a cell’s internal structures.
TEMs use electromagnets to focus the electron beam.

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14
Q

how does a scanning electron microscope work?

A

In a SEM, a beam of electrons moves back and forth across a cell’s surface, creating details of cell surface characteristics.
SEMs knock electrons off the specimen and these electrons come together to form an image.

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15
Q

limitations of TEM

A
  • specimens must be thin
  • 2d image
  • TEM must be performed in a vacuum
  • specimens must be dead
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16
Q

limitations of SEM

A
  • SEM has a lower resolution. Compared to TEM, the SEM provides lower resolution images.
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17
Q

advantages of TEM

A
  • A TEM produces very high-resolution images. TEM can be used to produce very detailed images of cell organelles
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18
Q

advantages of SEM

A

-SEM can produce 3D images of a specimen
- SEM can be used on thick specimens.

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19
Q

what’s magnification?

A

Magnification is the process of enlarging an object in appearance.

Magnification = size of image ÷ size of real object

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20
Q

what’s resolution?

A

Resolution is the ability of a microscope to distinguish two adjacent structures as separate.

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21
Q

what’s cell fractionation?

A

Cell fractionation separates organelles according to size to allow them to be studied in an electron microscope.

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22
Q

cell fractionation steps?

A

1- homogenisation: The tissue sample is homogenised using a blender to break the cells. tissue sample must be kept in cold isotonic buffered solution

2- filtration: The tissue sample is filtered into tubes through a gauze.

3- ultracentrifugation: The samples are spun at a low speed in a centrifuge.
Centrifugation separates the sample into fractions.
Heavier organelles are forced to the bottom of the tube.
Lighter organelles move towards the top.

4- ultracentrifugation: The supernatant is poured off and centrifuged at a higher speed to separate the next heaviest organelles (the nuclei).
This is repeated at increasingly higher speeds to separate each fraction.

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23
Q

cell organelles from heaviest to lightest…

A
  • Nucleus.
  • Chloroplasts.
  • Mitochondria.
  • Lysosomes.
  • Endoplasmic reticulum.
  • Ribosomes.
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24
Q

DNA replication occurs during the - - - - - - - - - - - - of the cell cycle?

A

interphase

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25
Q

Mitosis is the part of the cell cycle in which a eukaryotic cell…

A

divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication.

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26
Q

stages of mitosis?

A
  • interphase
  • prophase
  • metaphase
  • anaphase
  • telophase
  • cytokinesis
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27
Q

interphase

A
  • The cell prepares to divide.
  • DNA is replicated by semi-conservative replication. There are now two copies of every chromosome.
  • The organelles are also replicated.
  • More ATP is produced to be used in cell division.
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28
Q

prophase

A

-The nuclear envelope breaks down and the nucleolus disappears. Chromosomes are left floating in the cytoplasm.
- The chromosomes coil more tightly and become shorter and fatter. They can be seen under a light microscope.
- Small protein bundles called centrioles move to opposite poles of the cell.
- Microtubules form the mitotic spindle between the centrioles.

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29
Q

metaphase

A
  • The chromosomes line up along the mid-line of the cell.
  • In metaphase, the chromosomes are maximally condensed.
  • They are attached to the spindle by the centromere.
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30
Q

anaphase

A
  • The chromosomes break into two chromatids. The sister chromatids separate at the centromere.
  • The spindles contract and pull the chromatids to each pole of the cell.
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31
Q

telophase

A
  • The chromatids reach the opposite poles and begin to decondense (unravel), becoming chromosomes again.
  • Nuclear envelopes form around the chromosomes so there are now two nuclei.
32
Q

cytokinesis

A

The cytoplasm splits and two daughter cells are formed. The daughter cells are identical to the original cell and to each other.

33
Q

The role of spindle fibres attached to centromeres in the separation of chromatids.

A

The chromosomes break apart at the centromere.
- The spindle fibres begin pulling the sister chromatids away from each other to opposite poles of the cell. This splits the chromosome into two V-shaped sister chromatid structures.

34
Q

Uncontrolled cell division can lead to…

A

the formation of tumours and of cancers.

35
Q

Many cancer treatments are directed at…

A

controlling the rate of cell division.

36
Q

Binary fission in prokaryotic cells involves…

A
  • replication of the circular DNA and of plasmids
  • division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids.
37
Q

binary fission stages…

A

1) Replication of genetic material: Binary fission in prokaryotic cells involves replication of the circular DNA and of plasmids.

2) Migration of genetic material: The two sets of genetic material migrate towards opposite poles.

3) Cytoplasm begins to divide:
The cytoplasmic contents must be divided to give both new cells the machinery to sustain life.

4) Formation of daughter cells:
Two daughter cells are formed, each with a single copy of the circular DNA and a variable number of plasmid copies.
Daughter cells are genetically identical to the parent cells and identical to each other.
The only difference between the daughter cells is the number of plasmid copies in each cell

38
Q

why don’t viruses undergo cell division?

A

because they’re non living

39
Q

how do viruses replicate?

A

viral replication

40
Q

viral replication stages…

A
  • To replicate, viruses have to invade and hijack the reproductive mechanism of a living cell. These cells are then termed host cells.
  • Viruses have attachment glycoproteins that bind to complementary receptors on host cells.
  • They then inject DNA or RNA into the host cell.
  • The host cell divides as normal and the virus is replicated.
41
Q

simple diffusion

A

Simple Diffusion is the net movement of particles from an
area of higher concentration to an area of lower
concentration (down their concentration gradient).

42
Q

Facilitated diffusion

A

Facilitated diffusion is the net movement of particles down
their concentration gradient across a partially permeable cell membrane via carrier or channel proteins.

43
Q

Osmosis

A

Osmosis is the net movement of water from an area of
higher water potential to an area of lower water potential
across a partially permeable membrane.

44
Q

Active transport

A

This is the movement of particles from an area of low
concentration to an area of high concentration (against their concentration gradient) across a cell membrane, using ATP and carrier proteins.

45
Q

Co-transport of glucose and sodium ions

A
  1. Na+ ions are actively transported out of epithelial cells through a protein carrier molecule. 3 Na+ ions are transported out of the epithelial cells into the bloodstream in exchange for 2 K+ ions.
  2. The movement gives a higher concentration of Na+ ions in the lumen of the intestine rather than inside of the cell. This maintains the concentration gradient.
  3. Na+ ions move down the concentration gradient using a
    co-transport protein. Both Na+ and glucose can bind to the protein (the binding of one makes the other more
    effective). 2 Na+ and a glucose molecule must bind before
    they can be transported across the membrane.
  4. The glucose moves into the blood plasma using
    facilitated diffusion and a uniporter.
46
Q

Cells may be adapted for rapid transport across their internal or external membranes by an…

A

increase in surface area of, or by an increase in the number of protein channels and carrier molecules in, their membranes.

47
Q

what’s a pathogen?

A

Pathogens are organisms that cause disease.
- Most pathogens are micro-organisms (e.g. bacteria and viruses).
- Some pathogens are fungi or protists.

48
Q

Toxins are

A

harmful substances produced by pathogens.
Immune cells can detect the presence of toxins.

49
Q

antigens are…

A

molecules (proteins and glycoproteins) that are present on the cell surface membrane of all cells.
- Antigens signal to the immune system if the cells are ‘foreign’.

50
Q

antigenic variation is…

A

Pathogens are continually evolving to evade the immune system. One way in which they do this is by switching up the shape of their antigens, a process known as antigenic variation.

Memory cells that have formed from one viral strain may not detect the presence of antigens from other strains, so the person has to go through the primary immune response all over again.

51
Q

phagocytosis stages…

A

1- Pathogen is detected by a phagocyte

2- The phagocytes engulfs the pathogen. The pathogen is engulfed in a vesicle known as the phagosome.

3- Inside the phagocyte, the phagosome fuses with a lysosome. Upon fusion, the lysosome releases lysozymes into the phagosome which then hydrolyse the pathogen.

4- The phagocyte absorbs the digestive products.

52
Q

cellular response stages…
(The response of T lymphocytes to a foreign antigen)

A

1- Antigen from the pathogen is displayed on the cell surface of body cells or phagocytes after phagocytosis
2- T cells with the correct specific receptor bind with the antigen and are activated
3- They divide by mitosis (clonal expansion) and differentiate into T helper, cytotoxic and memory cells.

53
Q

function of T helper cells?

A

stimulates B cells to divide and secrete antibodies

54
Q

function of cytotoxic T cells…

A

kills abnormal cells and infected body cells via performing

55
Q

function of T memory cells…

A

remains in the blood for years and provide long term

56
Q

humoral immunity (response of B lymphocytes to a foreign antigen)

A

1- Free antigen binds to a complementary B cell receptor, activating the B cell (clonal selection)

2- The pathogen is endocytosed, and the antigen presented on the plasma membrane

3- T helper cell binds to the presented antigen and stimulates the B cell to divide by mitosis (clonal expansion)

4- The B cell differentiates to plasma and memory cells

57
Q

what’s a plasma cell?

A

secretes antibodies

58
Q

what’s an antibody?

A

Antibodies are a protein produced by lymphocytes in response to the presence of the corresponding antigen.

59
Q

how do antibodies work?

A

Antibodies agglutinate pathogens by forming antigen-antibody complexes, leading to phagocytosis & neutralise toxins.

60
Q

antibody structure…

A
  • antigen binding site
  • 2 heavy chains
  • 2 light chains
  • constant region
  • variable region
61
Q

what’s active immunity?

A

Active immunity occurs when specific antibodies are produced by the individual’s own immune system

62
Q

what’s passive immunity?

A

Passive immunity occurs when specific antibodies are introduced to the individual from an outside source.

63
Q

what’s vaccination?

A

Vaccination is the introduction into the body of a vaccine containing disease antigens, by injection or mouth, in order to induce artificial immunity

64
Q

what’s vaccination?

A

Vaccination is the introduction into the body of a vaccine containing disease antigens, by injection or mouth, in order to induce artificial immunity

65
Q

how do vaccines work?

A

Vaccines work by injecting weakened/dead pathogens into the body to stimulate an immune response, to form memory cells against the specific antigen, which destroy the pathogen quickly upon infection.

66
Q

what’s herd immunity?

A

Herd immunity is when the vaccination of a significant proportion of the population provides protection for individuals who have not developed immunity

67
Q

hiv structure

A
  • capsid
  • matrix
  • lipid envelope
  • attachment proteins
  • reverse transcriptase
  • RNA
68
Q

hiv replication stages…

A
  1. Attachment and Entry: HIV targets cells with CD4 receptors, mainly helper T cells.
  2. Fusion and Uncoating: After binding, HIV fuses with the cell membrane, releasing its RNA and enzymes into the host cell.
  3. Reverse Transcription: The reverse transcriptase enzyme converts the viral RNA into DNA
  4. The newly formed viral DNA, with the help of integrase, integrates into the host cell’s DNA.
  5. Replication: The integrated viral DNA hijacks the host’s cellular machinery to produce viral components – RNA and proteins.
    .
69
Q

how does HIV cause AIDS ?

A

The reduction in the number of T lymphocytes in the body due to HIV can then lead to the development of Acquired Immune Deficiency Syndrome (AIDS).

70
Q

why are antibiotics ineffective against viruses?

A

Viruses are surrounded by a protective protein coating; they don’t have cell walls that can be attacked by antibiotics like bacteria does. It is because of this that antibiotics don’t work on viruses.

71
Q

The use of monoclonal antibodies in:
targeting medication to specific cell types by attaching a therapeutic drug to an antibody

A

Drugs can be attached to monoclonal antibodies, in order to ensure the delivery of the drug to specific cell types e.g. cytotoxic drug to a cancer cell

72
Q

Ethical issues associated with the use of monoclonal antibodies.

A

Ethical considerations: treatment may cause death (risky), use of animals for production may cause harm, human trials

73
Q

Ethical issues associated with the use of vaccines?

A

Ethical considerations: side effects, financial cost, right to choose, animal testing of vaccines, human trials

74
Q

ELISA test

A
  • different monoclonal antibodies are bound to the surface of a well.
  • They attach to antigen present in a sample, allowing the attachment of a detection antibody.
  • An enzyme attached to the detection antibody digests a substrate, which is added, causing a colour change.
  • The colour intensity corresponds to the amount of the antigen present in the sample
75
Q

use of monoclonal antibodies

A

pregnancy testing

AQA AS Biology (6 decks)

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