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Biology A-level > 1 Cell Structure > Flashcards

1 Cell Structure Flashcards

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1
Q

Describe the structure of The cell-surface membrane. (Eukaryotic cell)

A
  • the membrane found on the surface of animal cells and just inside cell wall af other cells.
  • made of mainly lipids and proteins
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2
Q

Describe the function of The cell-surface membrane. (Eukaryotic cell)

A
  • regulates movement of substances into and out of cell

- has receptor molecules on it, which allow it to respond to chemicals like hormones.

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3
Q

Describe the structure of the nucleus. (Eukaryotic cell)

A
  • a large organelle surrounded by a nuclear envelope, which contains many pores
  • nucleus contains chromosomes, made from protein-bound linear DNA, and one or more nucleoli.
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4
Q

Describe the structure of a mitochondrion. (Eukaryotic cell)

A
  • usually oval-shaped
  • have a double-membrane, inner one is folded to form structures called Cristae
  • inside is the matrix, which contains enzymes involved in respiration.
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5
Q

Describe the function of a mitochondrion. (Eukaryotic cell)

A
  • site of aerobic respiration, where ATP is produced.

- found in large numbers in cells that are very active and require lots of energy.

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6
Q

Describe the structure of a chloroplast. (Eukaryotic cell)

A
  • small, flattened structure found in plants and algal cells
  • surrounded by double membrane.
  • has membranes inside called thylakoid membranes. These membranes stacked up to form grana, grana linked together by lamellae- thin, flat pieces of thylakoid membrane.
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7
Q

Describe the function of a chloroplast. (Eukaryotic cell)

A
  • site where photosynthesis occurs.
  • some parts of photosynthesis happen in grana, and other parts happen in the stroma (thick fluid found in chloroplasts).
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8
Q

Describe the structure of the Golgi apparatus. (Eukaryotic cell)

A
  • group of fluid-filled, membrane-bound flattened sacs.

- vesicles are often seen at edges of the sacs.

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9
Q

Describe the function of the Golgi apparatus. (Eukaryotic cell)

A
  • it processes and packages new lipids and proteins

- also makes lysosomes.

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10
Q

Describe the structure of the Golgi vesicle. (Eukaryotic cell)

A

-small fluid-filled sac in the cytoplasm, surrounded by a membrane and produced by the Golgi apparatus

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11
Q

Describe the function of the Golgi vesicle. (Eukaryotic cell)

A

-stores lipids and proteins made by Golgi apparatus and transports them out of the cell.

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12
Q

Describe the structure of a lysosomes . (Eukaryotic cell)

A

-a round organelle surrounded by a membrane, with no clear internal structure. It’s a type of Golgi vesicle.

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13
Q

Describe the function of a lysosomes . (Eukaryotic cell)

A
  • contains digestive enzymes called lysozymes. These are kept separate from the cytoplasm by surrounding membrane.
  • can be used to digest invading cells or to breakdown worn out components of the cell.
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14
Q

Describe the structure of a ribosome. (Eukaryotic cell)

A
  • very small organelle that either floats free in cytoplasm or is attached to the rough end opals is reticulum.
  • made up of proteins and RNA.
  • its not surrounded by a membrane.
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15
Q

Describe the function of a ribosome. (Eukaryotic cell)

A

-site where proteins are made.

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16
Q

Describe the structure of the rough endoplasmic reticulum. (Eukaryotic cell)

A
  • system of membranes enclosing a fluid-filled space.

- surface covered with ribosomes.

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17
Q

Describe the function of the rough endoplasmic reticulum. (Eukaryotic cell)

A

-folds and processes proteins that have been made at the ribosomes.

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18
Q

Describe the structure of the smooth endoplasmic reticulum. (Eukaryotic cell)

A

-system of membranes enclosing a fluid-filled space, with no ribosomes.

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19
Q

Describe the function of the smooth endoplasmic reticulum. (Eukaryotic cell)

A

-synthesis and processes lipids.

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20
Q

Describe the structure of the cell wall. (Eukaryotic cell)

A
  • rigid structure surrounding cells in plants, algae and fungi.
  • in plants and algae made mainly of carbohydrate cellulose.
  • in fungi made of chitin.
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21
Q

Describe the function of the cell wall. (Eukaryotic cell)

A

-supports cells and prevents them from changing shape.

22
Q

Describe the structure of the cell vacuole. (Eukaryotic cell)

A
  • membrane-bound organelle found in the cytoplasm of plant cells
  • contains cell sap, a weak solution of sugar and salts.
  • surrounding membrane called the tonoplast.
23
Q

Describe the function of the cell vacuole. (Eukaryotic cell)

A
  • helps maintain pressure inside cell and keeps cell rigid, this stops plants wilting.
  • also involved in isolation of unwanted chemicals inside the cell.
24
Q

Describe specialised cells.

A
  • In multicellular organisms, eukaryotic cells become specialised for specific functions.
  • specialised cells are organised into tissues, tissues into organs and organs into systems.
25
Q

What are tissues?

A

A group of cells working together to perform a particular function.

26
Q

How does a prokaryotic cell differ from a eukaryotic cell?

A

It has:

  • cytoplasm that lacks membrane-bound organelles
  • smaller ribosomes
  • no nucleus, instead they have a single circular DNA molecule that’s free in cytoplasm and not associated with proteins
  • cell wall that contains murein, a glycoprotein.
  • one or more plasmids
  • a capsule surrounding cell
  • 1 or more flagella
27
Q

Describe a virus.

A
  • acellular, just nuclei acids surrounded by protein.
  • smaller than bacteria
  • no plasma membrane, no cytoplasm, no ribosomes.
  • structure of virus particles to include genetic genetic material, capsid and attachment protein.
28
Q

What is the formula for magnification?

A

I
———
A x M

29
Q

Describe the advantages of a optical microscope.

A
  • easy to use
  • cheap
  • colour image
30
Q

Describe the disadvantages of a optical microscope.

A
  • much lower magnification and resolution

- can’t see small organelles. Eg. Ribosomes.

31
Q

Describe how transmission electron microscope work.

A

TEMs use electromagnets to focus a beam of electrons, which is then transmitted through the specimen. Denser parts of specimen absorb more electrons, which makes them look darker on the image you end up with.

32
Q

What are the advantages of using a transmission electron microscope?

A
  • better magnification and resolution that S.E.M, as its a shorter wavelength of electrons than light.
  • allows internal structures to be seen.
33
Q

What are the disadvantages of using a transmission electron microscope?

A
  • can’t look at living cells
  • specimens need to be in a vacuum
  • need to use a thin slice of specimens which can create artefacts
  • doesn’t for a colour image.
34
Q

Describe how a scanning electron microscope works.

A

SEMs scan a beam of electrons across specimen. This knocks off electrons from specimen, which are gathered in a cathode ray tube to form an image.

35
Q

What are the advantages of using a scanning electron microscope?

A
  • much better magnification and resolution than light microscopes as wavelength of electrons is shorter than wavelength of light
  • forms 3D image
  • don’t need to slice a thin section.
36
Q

What are the disadvantages of using a scanning electron microscope?

A
  • lower magnification and resolution than TEM

- can’t see internal structures.

37
Q

Define magnification.

A

How much bigger the image is than the specimen.

38
Q

Define resolution.

A

How detailed the image is. More specifically, it’s how well a microscope distinguishes between 2 points that are close together.

39
Q

What is the first step of cell fractionating.

A

Homogenisation- breaking up the cells.

  • can be done by vibrating cells or grinding cells up in blender to break up plasma membrane and release organelles into solution.
  • solution kept ice cold to prevent activity of enzymes that break down organelles
  • solution is isotonic to prevent osmosis so organelles don’t change size/shrivel/burst
40
Q

What is the second step of cell fractionating.

A

Filtration- getting rid of big bits

-filter solution through gauze to separate any large cell debris or tissue debris.

41
Q

What is the final step of cell fractionating.

A

Ultracentrifugation- separating organelles.

  • spin test tube in centrifuge.
  • heaviest organelles compressed into pellet at bottom.
  • remain liquid poured off, then test tube spun again.
  • next heaviest organelle remove in a pellet and then process is repeated.
  • heaviest is the nuclei then chloroplasts, then mitochondria and the lightest is ribosomes.
42
Q

Explain the cell cycle for eukaryotic cells that do retain the ability to divide.

A
  • divided into interphase (separated into G1,S and G2) and mitosis.
  • in G1, cell grows and new organelles and proteins are made.
  • in S(synthesis) cell replicates DNA, ready to divide by mitosis.
  • in G2, cell keeps growing and proteins needed for cell division are made.
  • mitosis is when eukaryotic cell divides to produce 2 identical daughter cells.
43
Q

Describe what happens in the interphase.

A

DNA and organelles replicate.

44
Q

Describe what happens in prophase.

A
  • chromosomes condensation and become visible.
  • nuclear membrane breaks down
  • centrioles move to the poles, forming network of proteins fibres across it called the spindle.
45
Q

Describe what happens in metaphase.

A
  • chromosomes line up on the equator.

- spindles attach to their centromeres.

46
Q

Describe what happens in anaphase.

A
  • centromeres divide, separating each pair of sister chromatids.
  • spindles contract, pulling chromatids to opposite poles of spindle.
47
Q

Describe what happens in telophase.

A
  • chromatids reach opposite poles on spindle. They uncoil and become long and thin again and now called chromosomes again.
  • nuclear envelope forms around each group of chromosomes, so now there are 2 nuclei.
  • cytoplasm divides (cytokinesis) to produce 2 genetically identical daughter cells.
48
Q

Explain uncontrolled cell division.

A
  • mutation in a gene that controls cell division, cells grow out of control.
  • cells keep on dividing to make more and more cells which forms a tumour.
  • cancer is a tumour that invades surrounding tissue.
49
Q

How do cancer treatments work?

A
  • some chemical drugs prevent synthesis of enzymes needed for DNA replication. If these aren’t produced cell unable to enter synthesis phase, irruption get cell cycle and forcing cell to kill itself.
  • radiation and some drugs damage DNA, at several points in cell cycle DNA checked for damage, if a age detected cell will kill itself, so preventing tumour growth.
50
Q

Describe how prokaryotic cells replicate by binary fission.

A
  • circular DNA and plasmid(s) replicate.
  • cell gets bigger and DNA loops move to opposite poles of cell
  • cytoplasm begins to divide and new cell walls begin to form.
  • cytoplasm divides and 2 daughter cells produced. Each with one copy of circular DNA and a variable umber of copies of plasmids.
51
Q

How do viruses replicate.

A
  • use attachment proteins to bind to complementary receptor proteins on surface of host cell.
  • inject their DNA or RNA into host cell, this hijacks the cell then uses its own machinery to replicate the viral particles.
52
Q

How to calculate mitosis index.

A

Number of cells with visible chromosomes / total number of cells observed.

Biology A-level (15 decks)

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