AQA A Level Biology > 2-3 Structure + Division > Flashcards

2-3 Structure + Division Flashcards

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1
Q

What is the resolution?

A

Clarity, is the furthest away an image can be while still remaining as two separate objects

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2
Q

What is the nucleus?

A
  • Contains hereditary material
  • Nuclear envelope: double membrane, the outer membrane is continuous with the ER, controls the entry and exit of material
  • Nuclear pores: allows the passage of large molecules out of the cell
  • Nucleoplasm
  • Chromosomes: protein-bound DNA
  • Nucleolus: makes ribosomal RNA, assembles ribosomes
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3
Q

What are ribosomes?

A
  • Two subunits
  • Contains RNA and protein
  • Site of protein synthesis
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4
Q

What is the SER?

A
  • Lacks ribosomes

- Synthesises, stores and transports lipids and carbohydrates

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5
Q

What is the RER?

A
  • Has ribosomes present on the outer surface of the membrane

- Large surface area for the synthesis of proteins

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6
Q

What is the Golgi apparatus?

A
  • Flattened sacs or cisternae
  • Vesicles bring material from the ER
  • Processes and packages material
  • Produces secretory enzymes
  • Transports, modifies and stores lipids
  • Forms lysosomes
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7
Q

What are the lysosomes?

A
  • Hydrolyses material ingested by phagocytes
  • Exocytosis destroys material
  • Digests worn out organelles
  • Autolysis
  • Contains lysozymes which hydrolyse cell walls
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8
Q

What are the mitochondria?

A
  • A double membrane which controls the entry and exit of material
  • Cristae: extensions of the inner membrane, large surface area for respiration
  • Matrix: contains all the substances needed for respiration
  • Creates ATP
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9
Q

What is the vacuole?

A
  • Fluid-filled sac
  • A single membrane called a tonoplast
  • Contains pigments to attract pollinating insects
  • Temporary food store
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10
Q

What are chloroplasts?

A
  • Chloroplast envelope: double membrane, controls the entry and exit of material
  • Grana: stacks of thylakoids
  • Thylakoids: contains chlorophyll, some have extensions between adjacent grana
  • Stroma: a fluid-filled matrix that possesses all the enzymes needed for photosynthesis
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11
Q

How are chloroplasts adapted for photosynthesis?

A
  • Granal membranes provide a large surface area
  • Fluid possesses all the enzymes needed for sugar production
  • Contain both DNA and ribosomes to manufacture the proteins needed for photosynthesis
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12
Q

What is the difference between ribosomes in eukaryotic and prokaryotic cells?

A

80S: eukaryotic
70S: prokaryotic, found in mitochondria and chloroplasts

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13
Q

What is the cell wall?

A
  • Found in all plant cells
  • Consists of microfibrils of cellulose
  • Middle lamella marks the boundary between cell walls
  • Stops the cell from bursting under osmotic pressure
  • Strengthens the plant cell
  • Allows the movement of water
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14
Q

What is a tissue?

A

A group of similar cells that perform a specific function

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15
Q

What is epithelial tissue?

A

It consists of sheets of cells
It lines the surface of organs
Most have a protectors or secretory function

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16
Q

What is xylem tissue?

A

Found in plants
Used to transport water and mineral ions through the plant
Gives mechanical support

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17
Q

What is an organ?

A

A structure composing of two or more tissues which undergo one major function

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18
Q

What is an organ system?

A

A group of organs working together to perform a particular function

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19
Q

What is connective tissue?

A

The supporting tissue of the body

It binds structures together to provide support and protection against damage/infection/heat loss

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20
Q

What are prokaryotic cells?

A

They have no nucleus

Instead they have a single circular DNA molecule that is free in the cytoplasm and not associated with proteins

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21
Q

What are the differences between prokaryotic and eukaryotic cells in terms of cell walls?

A

P: have rigid cell walls made of polysaccharide and protein
E: have rigid cell walls mostly made of cellulose and only found in plant cells

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22
Q

What are the differences between prokaryotic and eukaryotic cells in terms of flagella?

A

P: have simple flagella
E: may have complex extension of cytoplasm to form cilia for coordinated movement

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23
Q

What are the differences between prokaryotic and eukaryotic cells in terms of respiration?

A

P: bacteria have mesosomes and algae use cytoplasmic membranes
E: have mitochondria

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24
Q

What are the differences between prokaryotic and eukaryotic cells in terms of photosynthesis?

A

P: no chloroplasts, only bacterial chlorophyll associated with the cell surface membrane in some bacteria
E: plant and algae cells contain chloroplasts

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25
What are the differences between prokaryotic and eukaryotic cells in terms of fixing nitrogen?
P: some have the ability to fix nitrogen E: cannot fix nitrogen
26
What are the differences between prokaryotic and eukaryotic cells in terms of a capsule?
P: many have an outer mucilaginous layer called a capsule E: don't have a capsule
27
What is the structure of a bacterial cell?
Cell wall: made of murein Capsule: outer mucilaginous layer, only found in some species Cell surface membrane Plasmid: small, circular pieces of DNA Flagellum: can be more than one, for movement Cytoplasm: contains enzymes and other soluble material Ribosomes: 70S
28
What is a virus?
Smallest structure that shows life- 20-300nm Genetic material: DNA or RNA but not both, small number of genes Can't be treated with antibiotics because there are no metabolic processes for them to inhibit Can only multiply inside a host cell
29
What is the structure of viruses?
Lipid envelope Attachment proteins Matrix Capsid Genetic material (RNA) Reverse transcriptase
30
What is the difference between prokaryotic and eukaryotic cells in terms of nuclei?
P: no true nucleus, only an area where DNA is found E: distinct nucleus with a nuclear envelope
31
What is the difference between prokaryotic and eukaryotic cells in terms of DNA?
P: DNA is not associated with proteins, some DNA is in the form of circular strands called plasmids E: DNA is associated with proteins called histones, there are no plasmids, and DNA is linear
32
What is the role of the cell wall in bacterial cells?
Physical barrier which protects the cell against mechanical damage, certain substances and osmotic lysis
33
What is the role of the capsule in bacterial cells?
Protects bacterium from other cells and helps to group bacteria to stick together for further protection
34
What is the role of the cell-surface membrane in bacterial cells?
Controls the entry and exit of materials
35
What is the role of circular DNA in bacterial cells?
Possesses the genetic information for the replication of bacterial cells
36
What is the role of plasmids in bacterial cells?
Possesses genes that may aid the survival of bacteria in adverse conditions
37
What are unit conversions below millimetres?
There are 1000 nm in an µm | There are 1000 µm in a millimetre
38
What is magnification?
The degree to which the size of an image is bigger than the size of an object
39
What is a compound light microscope?
Light passed through a specimen, image formed on human retina, focused by glass lenses Max magnification is about 1000, 500X better than the human eye Resolves objects separated by 0.2 micrometers Needs very thin specimens Can be stained to show colours Is portable
40
What is an electron microscope?
Electrons are absorbed or deflected by molecules in air so a near vacuum has to be created Beam can be focused using electromagnets because electrons are negatively charged Greater resolving power is due to the electron beam having a shorter wavelength than light
41
What is a transmission electron microscope?
Consists of an electron gun, electrons pass through the specimen, beam is focused by magnetic lenses, image formed by fluorescent screen Max magnification is millions Resolves objects separated by 0.02 nanometers Specimen must be extremely thin to allow electrons to penetrate Complex staining process doesn't create a coloured image The high powered electron beam can destroy the specimen Image may contain artefacts
42
What is a scanning electron microscope?
Specimens don't need to be thin as electrons don't penetrate Specimen is sprayed with a thin coating of metal, electron beam is scanned across the surface of the specimen, metal emits secondary electrons Emitted electrons can be focused by magnetic lenses Image formed on fluorescent screens Resolving power of 20nm, 10X better than light microscope Creates a 3D image that is created by a computer analysis of the scattered electrons
43
What is a centrifuge?
It is a device that spins very fast in order to separate liquids by masses
44
What is differential centrifugation?
It is the separation of the different organelles within the cell
45
What is homogenation?
It is the process of blending cells | Homogenate is the resultant fluid
46
What is the method for differential centrifugation?
Cut tissue in an ice-cold isotonic buffer (cold to stop enzyme activity, isotonic to stop osmosis, buffer to stop pH changes) Grind tissue in a filter to break down cells Filter to remove insoluble cells Place in a centrifuge at different speeds to separate the components
47
What are the vague speeds for separation in differential centrifugation?
``` Low = nuclei Faster = mitochondria and chloroplasts Faster = ER, Golgi and other membrane fragments Fastest = ribosomes ```
48
What is interphase stage of mitosis?
Gap 1 = cell growth, normal function DNA synthesis = DNA is copied Gap 2 = additional growth, chromatids become replicated chromosomes, centriole replicates
49
What is the prophase stage of mitosis?
Chromosomes condense and become visible as they stain more intensely Nuclear envelope breaks up into small vesicles Nucleolus forms part of several chromosomes Centrioles separate and take positions on opposite poles of the cell Single fibres form and radiate towards the centre of the cell
50
What is metaphase in mitosis?
Shortest phase Chromosomes line up in the middle of the cell Spindle fibres connect to the centromere of each sister chromatid
51
What is anaphase in mitosis?
Spindle fibres start to contract Centromeres that join the sister chromatid split Sister chromatids are pulled apart Separated chromatids move to opposite poles of the cell Centromeres move first
52
What is telophase in mitosis?
Chromosomes each consisting of a chromatid uncoil A nuclear envelope forms around the chromosomes at each pole of the cell Spindle fibres break down and dissolve Cytokinesis begins
53
What is cytokinesis?
The division of the cytoplasm that creates two separate cells Made by constriction from the edge of the cell Process differs in plant and animals Animal cytokinesis: cell membrane forms a cleavage furrow that eventually pinches the cell into two clearly equal parts, each part containing its own nucleus
54
Does mitosis occur if the cell is damaged?
No | An uncontrollable process can lead to tumours or cancer
55
What is binary fission?
Occurs in prokaryotic cells The circular DNA and plasmids replicate The cytoplasm then divides to produce two daughter cells Each daughter cell has a single copy of the circular DNA and a variable number of copies of plasmids
56
Do viruses undergo cell division?
They don't | They inject nucleic acid into the host cell so that the host will replicate the virus particles
57
What is a somatic cell?
A typical body cell with twice the number of chromosomes as the gamete
58
What are the factors that regulate the cell cycle?
Before a cell divides, the DNA is checked to make sure it has replicated correctly A gene mutation occurs if DNA doesn't copy directly Chemical signals tell a cell when to stop or start dividing Neighbouring cells communicate with dividing cells to regulate growth Cancer is a disease of the cell cycle, some of the body's cells divide uncontrollably and tumours form Cancer can be caused by smoking, radiation, pollution and other chemicals. It can also occur naturally
59
How do you calculate the mitotic index?
Mitotic cells ----------------- X 100 Total cells
60
How do you calculate magnification?
size of image ------------------------- = magnification size of real object
61
Why is tissue placed in an ice-cold, isotonic buffer solution?
Ice-cold to prevent enzyme activity Isotonic to prevent osmosis Buffer to prevent pH changes
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