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AQA A-Level Biology > GA2 > Flashcards

GA2 Flashcards

1
Q

What does ‘magnification’ mean?

A

The process of enlarging the physical image or appearance of something.

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2
Q

What does resolution mean?

A

The ability to distinguish between two points as separate structures.

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3
Q

How to you work out image size?

A

Image = Actual size x magnification

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4
Q

How do you work out the total magnification?

A

Total magnification = eyepiece lens x objective lens

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5
Q

What is the maximum magnification of a light microscope?

A

X1500

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6
Q

What is the maximum resolution of a light microscope?

A

0.0001mm

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7
Q

What is the maximum magnification of an electron microscope?

A

X2000000

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8
Q

What is the maximum resolution of an electron microscope?

A

2.0x10-7

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9
Q

What does differentiation mean?

A

“Making them adapted to carry out a particular function”

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10
Q

What can cell differentiation cause changes to?

A
  • The number or size of a particular organelle found in a cell. (Eg mitochondria in a muscle cell)
  • The shape of the cell
  • Changes to some of the contents of a cell (eg red blood cells having no nucleus)
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11
Q

Tissues

A
  • Animal and plant cells can form tissues
  • A living tissue is made up from a group of cells with a similar structure and function, which all work together to do a particular job.
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12
Q

Organs

A
  • An organ is made from a group of different tissues, which all work together to do a particular job.
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13
Q

Organ System

A
  • An organ system is made from a group of different organs, which all work together to do a particular job.
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14
Q

What is cell fractionation?

A
  • Process where cells are broken up and different organelles they contain spread out.
  • It is used to help us study cell organelle structures and function.
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15
Q

What must the tissue be before cell fractionation?

A
  • Cold = reduces enzyme activity
  • Isotonic = to make sure cells don’t burst or swell
  • Buffered = keeps it a sensible ph so proteins aren’t denatured.
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16
Q

Process of cell fractionation

A
  • Cells are homogenised (broken up) and are in a solution called homogenate.
  • filtered to remove any large cells/ debris
  • some homogenate is put in a test tube and centrifuged. The pellet is then removed where the nuclei will be (first to come out)
  • This process is then repeated until the organelle wanting to be studied is spun out.
17
Q

What order do organelles come out the centrifuge?

A
  • Nuclei
  • Chloroplasts
  • Mitochondria
  • Lysosomes
  • Endoplasmic reticulum
  • Ribosomes
18
Q

What is DNA?

A

A molecule which carries the instructions (genes) which control the activity of the cell.

19
Q

What is chromatin?

A

The DNA & histone proteins together

20
Q

Relaxed single chromosome

A

One long, linear DNA molecule, histone proteins and the centromere. Single chromosomes are not visible under a light microscope.

21
Q

Relaxed duplicated chromosome

A

Before a cell divides, chromosomes are replicated. Each chromosome consists of two genetically identical copies called sister chromatids, held together by a centromere.

22
Q

Supercoiled duplicated chromosome

A

During mitosis chromosomes shorten and thicken so they are sturdy enough to move round the cell. Individual chromosomes are only visible when supercoiled.

23
Q

What is the cell cycle?

A

Describes the events that take place as one cell divides to produce two new daughter cells which then grow to full size.

24
Q

What main stages is the cell cycle divided into?

A

Interphase, mitosis and cytokinesis.

25
Q

What are the subdivides of interphase?

+ definition

A

G1 - Protein synthesis and replication of organelles
S - DNA replication, each chromosome becomes two genetically identical copies (chromatids)
G2 - Growth of the cell

26
Q

Mitosis

A
  • Prophase : chromosomes condense so become visible, nuclear envelope disappears, centrioles move to poles and make spindle fibres.
  • Metaphase : chromosomes attach to spindle fibres by their centromeres and move to middle.
  • Anaphase : centromeres split, spindle fibres contract and shorten, chromatids pulled apart and move to opposite poles.
  • Telophase : nuclear envelopes form around relaxed chromosomes, two nuclei form, cell goes into cytokinesis.
27
Q

Cytokinesis

A

Cytoplasm and cell membrane splits creating two full daughter cells.

28
Q

Mitotic index calculation

A

Number of cells with visible chromosomes / total number of cells

29
Q

What does a high mitotic index mean?

A

Cell division is occurring rapidly.

Could be because tissue is growing rapidly, tissue is repairing, tissue is dividing uncontrollably (indicating cancer)

AQA A-Level Biology (1 decks)

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