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AS Level Biology flashcards > Biology Topic 2 - Cells > Flashcards

Biology Topic 2 - Cells Flashcards

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1
Q

What are lysosomes?
(Eukaryotes)

A

A membrane-bound organelle that releases hydrolytic enzymes.

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2
Q

What organisms have a cell wall?

A

Plants, algae and fungi.

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3
Q

What is the nucleus? What is its function?
(Eukaryotes)

A

A nucleus is a double membrane.
- It has nuclear pores that allows molecules to enter and leave.
- It has a nucleolus which is the site of ribosome production.

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4
Q

What is the rough endoplasmic reticulum? What is its function?
(Eukaryotes)

A

Flattened sacs enclosed by a membrane with ribosomes on the surface. It folds and process proteins made on the ribosomes.

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5
Q

What is the smooth endoplasmic reticulum? What is its function?
(Eukaryotes)

A

A system of membrane bound sacs without ribosomes on its surface. It produces and processes lipids.

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6
Q

What is the golgi apparatus? What is its function?
(Eukaryotes)

A

It is a series of fluid filled sacs with vesicles surrounding the edges. It process and packages proteins and lipids. It also produces lysosomes.

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7
Q

What are the mitochondria? What is its function?
(Eukaryotes)

A

They are bound by a double membrane (the envelope). The inner membrane is folded, producing projections called cristae - with a matrix on the inside. The matrix contains enzymes needed for respiration.

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8
Q

What are centrioles? (Eukaryotes)

A

They are involved in producing spindle fibres for cell division.

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9
Q

What are ribosomes composed of? (Eukaryotes)

A

They are composed of two sub-units and are the site of protein production.

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10
Q

What is an example of a prokaryotic cell?

A

Bacterial cells.

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11
Q

What are the features of prokaryotic cells?

A
  • They are much smaller than eukaryotic cells.
  • Their cytoplasm does not have membrane-bound organelles.
  • They have a single circular DNA molecule that isn’t associated with proteins.
  • They have a cell wall that contains murein: a glycoprotein.
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12
Q

What is the capsule? (Prokaryotes)

A

A protective layer which helps the cell retain moisture stick to surfaces.

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13
Q

What structural features does a virus have?

A

he structure of virus
includes genetic material, capsid and attachment protein.

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14
Q

What do viruses consist of?

A

They consist of nucleic acid (either DNA or RNA) enclosed in a protein coat, the capsid.

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15
Q

What are 3 features that many prokaryotic cells have?

A
  • One or more plasmids.
  • A capsule surrounding the cell.
  • One or more flagella.
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16
Q

What are light microscopes?

A
  • Microscopes with a lower resolution, as they have a longer wavelength of light.
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17
Q

What are the two types of electron microscopes?

A
  • Transmission electron microscopes and scanning electron microscopes.
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18
Q

What are electron microscopes?

A
  • Microscopes that use a beam of electrons to resolve images.
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19
Q

What images do TEMs produce?

A
  • TEMs produce a 2D image. They can only be used for thin tissues, as thick specimens easily absorb the electrons.
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20
Q

What images do SEMs produce?

A
  • SEMs produced a 3D image.
  • They can be used for slightly thicker cells than TEM.
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21
Q

What are the limitations for TEM and SEM?

A
  • The whole system must be in a vacuum so living specimens cannot be observed.
  • A complex staining process is required which may introduce artefacts into the image.
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22
Q

What does resolution mean?

A
  • The minimum distance apart that two objects can be distinguished as separate objects in an image.
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23
Q

What does magnification mean?

A
  • How many times bigger the image of a specimen observed is in comparison to the actual (real-life) size of the specimen.
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24
Q

What is cell fractionation?

A

The process in which different parts and organelles of a cell is separated so that they can be studied in detail.

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25
Q

What are the steps of homogenisation?

A

1) Cells are homogenised in order to remove cellular debris.
2) This solution is placed in a centrifuge, and spun at slow speeds.
3) The heaviest organelle (nuclei) settle at the bottom of the tube where a pellet forms.
4) The supernatant is then spun at a slightly faster speed, removing the next heaviest organelle.
5) This process is repeated at increasing speeds.

26
Q

What conditions does the solution need to be under?

A
  • Solution must be cold, buffered and of the same WP as the cells.
  • This prevents organelles from bursting under osmotic pressure, to prevent enzymes from breaking down organelles (activity), to prevent pH fluctuations.
27
Q

Name the order of the mass of organelles, from heaviest to lightest.

A

Nuclei.
Chloroplasts (if carrying out cell fractionation of plant tissue)
Mitochondria.
Lysosomes.
Endoplasmic reticulum.
Ribosomes.

28
Q

What stage of the cell cycle does DNA replication occur in?

A

DNA replication occurs during the interphase of the cell cycle.

29
Q

What is mitosis?

A

Mitosis relates to cell division that produces identical cells for growth and asexual reproduction.

30
Q

What are three stages of the cell cycle?

A

1) Mitosis.
2) Interphase.
3) Cytokinesis.

31
Q

What stages is mitosis broken down into?

A
  • PMAT, prophase, metaphase, anaphase and telophase.
32
Q

What happens in interphase?

A

The cell grows and prepares to divide. Chromosomes and some organelles are replicated. Chromosomes also begin to condense.

33
Q

What happens during cytokinesis?

A

The parent and replicated organelles move to opposite sides of the cell and the cytoplasm divides, producing two daughter cells.

34
Q

Mitosis is important for growth and repair. How does it allow for these processes to happen?

A

Growth = all cells produced are identical, so organisms can grow using mitosis.

Repair = all cells produced are identical, so organisms can replace dead tissues using mitosis.

35
Q

What is interphase?
What are the 3 phases of interphase?

A

Interphase is a phase where the cell grows and DNA is replicated. Cell growth occurs in preparation for division.
The three phases are G1, S and G2.

36
Q

What happens in the G2 phase?

A

Loosely coiled replicated chromosomes are present.
Sister chromatids are held together at the centromere.

37
Q

What happens during prophase?

A

The nuclear envelope is broken down and chromosomes are fully condensed.
- Spindle fibres appear, starting to attach to chromosomes.

38
Q

What happens during metaphase?

A

Chromosomes align at the centre of the cell.

39
Q

What happens during anaphase?

A

The centromeres divide. Sister chromatids moves to opposite poles of the cell.

40
Q

What happens during telophase?

A

The nuclear membrane reforms and chromosomes decondense. Spindle fibres now disappear.

41
Q

What happens during cytokinesis?

A

The cytoplasm divides and the parent cell becomes 2 daughter cells with identical genetic information.

42
Q

Why does regular mitosis not lead to cancers or tumours forming?

A

Mitosis is a controlled process. Only uncontrolled cell division leads to the formation of tumours or cancers.

43
Q

What are cancer treatments directed at?

A

Many cancer
treatments are directed at controlling the rate of cell division.

44
Q

Describe the process of binary fission in prokaryotic cells.

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.
45
Q

As viruses do not under cell division because they are non-living, how do they replicate?

A

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

46
Q

How did the cell-membrane receive the name ‘fluid-mosaic model’?

A

The fluidity of the membrane and the mosaic arrangement of the protein give the structure
of the membrane its name.

47
Q

Does cholesterols presence impact the movement of other molecules?

A

It restricts the movement of other molecules making up the membrane. This is because it used to make the membrane more rigid, reducing the movement of phospholipids.

48
Q

What kind of molecules does the structure of the phospholipid bilayer allow to pass through?
(Hydrophobic tails inward, heads pointing outward).

A

It allows lipid solid molecules to pass through, but not water soluble molecules.

49
Q

How are proteins found in the cell membranes?

A

They may be integrated throughout the membrane, or may be on the surface (extrinsic). Intrinsic proteins such as carrier proteins allow substances to cross the membrane.
- They also provide mechanical support.

50
Q

What are glycolipids? How are glycolipids found in the membrane?

A
  • Glycolipids are made up of a carbohydrate that is bound to lipids.
  • They act as cell surface receptors for certain molecules. They can adhere to one another to form tissues.
51
Q

What are glycoproteins? How are glycoproteins found in the membrane?

A
  • These are carbohydrates that attach to extrinsic proteins, acting as a cell surface receptor and a neurotransmitter.
    They allow cells to recognise each other, as well as attach to form tissues.
52
Q

What are the different types of movement?

A

Diffusion, facilitated diffusion, osmosis, active transport, co-transport.

53
Q

What is diffusion?

A

The passive movement of non-polar, lipid-soluble molecules from high -> low concentration. Molecules are moved straight through the phospholipid layer.

54
Q

What is facilitated diffusion?

A

A channel protein in the cell membrane is used to transport polar molecules, charged and water-soluble molecules across the membrane.

55
Q

What is osmosis?

A

Osmosis is the diffusion of water molecules from a high WP -> an area of low WP through a partially permeable membrane.

56
Q

What is active transport?

A

A process by which all types of molecules are transported through carrier proteins from an area of low -> high concentration. This process requires energy in the form of ATP.

57
Q

What is co-transport? How does the process lower the cocentration of Na and K ions in the cell?

A

Co-transport is a process by which ions are used to move substances in and out of cells. In the epithelial cells found in the ileum, sodium and potassium ions are pumped out of the epithelial cell by active transport into the blood, leaving a lower concentration in the cell.

58
Q

When there is a lower concentration of Na and K ions present in the cell, how do the ions move in again?

A

As a result of the lower concentration in the cell, the ions move in from the lumen by facilitated diffusion - bringing glucose and amino acids into the cell at the same time.

59
Q

After the ions have moved in again and brought glucose and amino acids with them, what happens next?

A

These can then diffuse from a high concentration in the epithelial cell to a low concentration in the blood.

60
Q

What factors make the rate of gas exchange by diffusion become more rapid?

A
  • An increase in surface area, a steeper diffusion gradient, a decrease in the diffusion distance, an increase in temperature.
61
Q

What does each cell have on its surface? How does this help the immune system?

A

Each type of cell has specific molecules, proteins, on its surface that enable the immune system to identify pathogens, cells from other organisms of the same species and abnormal body cells.

62
Q
A

AS Level Biology flashcards (5 decks)

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