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A - Level Biology AQA > Topic 2 - Cells > Flashcards

Topic 2 - Cells Flashcards

1
Q

What is the Golgi apparatus?

A

A series of fluid filled, flattened and curved sacs with vesicles surrounding the edges. It processes and packages proteins and lipids

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2
Q

Define cell fractionation

A

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

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3
Q

Give the first stage of homogenisation

A

The cells are first blended in an homogeniser forming the resultant fluid called the homogenate. This tube of homogenate is then placed in a centrifuge and spun at a low speed

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4
Q

Give the second stage of homogenisation

A

The heaviest organelles, the nuclei, are forced to the bottom of the tube where a thin sediment or pellet forms

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5
Q

Give the third stage of homogenisation

A

The fluid at the top, called the supernatant, is removed which leaves just the sediment of the nuclei. The supernatant is then transferred to another tube and spun at a slightly faster speed. This time the pellet that forms contains the next heaviest organelle, the mitochondria.

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6
Q

Give the fourth stage of homogenisation

A

This process continues so that each time the speed is increased the next heaviest organelle is sedimented and separated out

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7
Q

Give the conditions of the homogenate at the beginning of homogenisation and explain why

A

The homogenate at the beginning is placed in a cold, buffered solution of the same water potential as the cells. This is to prevent the organelles from bursting under osmotic pressure, to inactivate any enzymes from breaking down organelles and so that the pH does not fluctuate

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8
Q

What is the nucleus? (Talk about structure too)

A

Nucleus is a double membrane called the envelope containing - 3000 nuclear pores that enables molecules to enter and leave
It also contains chromatin and a nucleolus which is the site of ribosome production

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9
Q

What is the rough endoplasmic reticulum?

A

RER is a series of flattened sacs enclosed by a membrane with ribosomes on the surface

RER folds folds and processes proteins made on the ribosomes

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10
Q

What is the smooth endoplasmic reticulum?

A

SER is a system of membrane bound sacs

SER produces and processes lipids

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11
Q

What are mitochondria? (Discuss structure)

A

They are oval shaped, bound by a double membrane called the envelope

The inner membrane is folded to form projections called cristae with a matrix on the inside containing all the enzymes needed for respiration

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12
Q

What are centrioles?

A

Hollow cylinders containing a ring of microtubules arranged at right angles to each other

Centrioles are involved in producing spindle fibres for cell division

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13
Q

What are ribosomes?

A

Ribosomes are composed of two sub units and are the site of protein production

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14
Q

What are lysosomes?

A

Lysosomes are vesicles containing digestive enzymes bound by a single membrane

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15
Q

What are the two types of electron microscope?

A

Transmission and Scanning

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16
Q

State what happens in a Transmission Electron Microscope (TEM)?

A

A beam of electrons passes through thin section of a specimen. Areas that absorb the electrons appear darker on the electron micrograph that is produced

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17
Q

State what happens in a Scanning Electron Microscope (SEM)?

A

A beam of electrons passes across the surface and scatter. The pattern of scattering builds up a 3D image depending on the contours of the specimen

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18
Q

Give the limitations of an electron microscope

A

The whole system must be in a vacuum so living specimens cannot be observed

Specimens must be very thin, particularly for TEM so that electrons can pass through

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19
Q

What are viruses?

A

Viruses are non-living structures which consist of nucleic acid (either DNA or RNA) enclosed in a protein coat called the capsid, sometimes covered with a lipid layer called the envelope

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20
Q

State what happens in Interphase

A

The cell grows and prepares to divide - chromosomes and some organelles are replicated

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21
Q

State what happens in cytokinesis

A

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

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22
Q

Describe what happens during Prophase

A

Nuclear membrane breaks down
Chromosomes condense
Spindle fibres appear

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23
Q

Describe what happens during Prometaphase

A

Spindle fibers attach to chromosomes
Chromosomes condense

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24
Q

Describe what happens during Metaphase

A

Chromosomes align

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25
Describe what happens during Anaphase
Centromeres divide Sister chromatids move to opposite poles
26
Describe what happens during Telophase
Nuclear membrane reforms Chromosomes decondense Spindle fibers disappear
27
Give the seven structures of a prokaryotic cell
Cell Wall Capsule Plasmid Flagellum Pili Ribosomes Mesosomes
28
What is the cell wall? (Bacteria)
Rigid outer covering made of peptidoglycan
29
What is the capsule?
Protective slimy layer which helps the cell to retain moisture and adhere to surfaces
30
What is the plasmid?
Circular piece of DNA
31
What is the flagellum?
A tail like structure which rotates to move the cell
32
What is the Pili?
Hair-like structures which attach to other bacterial cells
33
What are ribosomes?
Site of protein production
34
What are Mesosomes?
Infoldings of the inner membrane which contains enzymes required for respiration
35
What are the main molecules in cell membranes?
Phospholipids
36
What happens when cell surface membranes are in an aqueous environment?
Phospholipid molecules form a bilayer A hydrophobic barrier is formed between the inside and outside of a cell
37
How are phospholipids arranged in a cell-surface membrane?
Hydrophobic tails orientated to the inside and the hydrophilic tails orientated to the outside
38
Give the functions of phospholipids in a membrane
Allow lipid-soluble substances to enter and leave the cell Prevent water-soluble substances entering and leaving the cell Make the membrane flexible and self-sealing
39
Give the purpose of surface proteins in a membrane
Occur in the surface of the bilayer never extend completely across it. Give mechanical support to membrane or work in conjunction with glycolipids, acting as cell receptors for molecules such as hormones
40
Give the purpose of Protein Channels in a membrane
Form water-filled tubes Allow water-soluble ions to diffuse across the membrane
41
Give the purpose of Carrier Proteins in a membrane
Bind to ions or molecules glucose or amino acids Change shape in order to these molecules membrane
42
Give the three functions of Cholesterol in a membrane
Strengthen membrane - reduce lateral movement of other molecules including phospholipids, by pulling together fatty acid tails Make the membrane less fluid at high temperatures Very hydrophobic - Prevent leakage of water and dissolved ions from the cellG
43
What is a glycolipid?
Made up of a carbohydrate covalently bonded with a lipid
44
What allows the cell to receive certain chemicals?
The carbohydrate potion from a glycolipid extends from the phospholipid bilayer into the water environment outside the cell
45
Give the three functions of glycolipids
Act as recognition sites (antigens) Help maintain stability of membrane Help cells attach to one another to form tissues
46
What are glycoproteins?
A carbohydrate chain attached to an extrinsic protein on the surface of the membrane Again, can act as cell-surface receptors, more specifically for hormones and neurotransmitters
47
Give the functions of glycoproteins
Help cells attach to one another to form tissues Allow cells to recognise one another
48
What is diffusion?
The passive movement of small, non-polar, lipid soluble molecules from an area of high concentration to an area of low concentration The molecules move directly through the phospholipid bilayer
49
What is facilitated diffusion?
Requires a channel protein in the cell membrane to transport polar molecules, charged and water soluble molecules across the membrane
50
What do exocytosis and endocytosis both do?
Transport large particles The particles are enclosed in vesicles made from the cell surface membrane
51
State what happens during endocytosis
Particles are transported into the cell
52
State what happens during exocytosis
Vesicles containing large particles are fused with the cell surface membrane and released from the cell
53
What is Co-Transport?
Co-Transport uses ions to move substances into and out of cells
54
What is binary fission?
The process by which prokaryotic cells divide
55
Give the first stage of binary fission
The circular DNA in the cells replicates and both copies attach to the cell membrane Plasmids also replicate
56
Give the second stage of binary fission
The cell membrane then begins to grow between the two DNA molecules and begins to pinch inwards, dividing the cytoplasm in two.
57
Give the third stage of binary fission
A new cell wall forms between the two DNA molecules dividing the original cell. The identical daughter cells each have a single copy of the circular DNA and a variable number of copies of the plasmids.
58
Define water potential
The pressure created by water molecules
59
What does pure water have a potential of?
Zero
60
What happens to the water potential when solutes are dissolved in it?
It becomes more negative. The more negative the water potential, the more solute must be dissolved in it.
61
What is an isotonic solution?
When the water potential is the same in the solution and the cell within the solution
62
What is a hypotonic solution?
When the water potential of a solution is more positive (closer to zero) than the cell
63
What is a hypertonic solution?
When the water potential of a solution is more negative than the cell

A - Level Biology AQA (5 decks)

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