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AQA Biology A level > Cells > Flashcards

Cells Flashcards

1
Q

Nucleus structure

A

Usually spherical with diameter of between 10 and 20µm

Nuclear envelope

Nuclear pores

Nucleoplasm

Chromosomes

Nucleolus

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2
Q

Nuclear envelope

A

Double membrane that surrounds nucleus

Outer membrane is continuous with the E.R. and often has ribosomes on its surface

Controls the entry and exit of materials and controls the reactions taking place within

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3
Q

Nuclear pores

A

40-100nm in diameter

Around 3000 pores in each nucleus

Allow the passage of large molecules, such as messenger RNA out of the nucleus

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4
Q

Nucleoplasm

A

Granular jelly-like material that makes up the bulk of the nucleus

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5
Q

Chromosomes (nucleus)

A

Consist of protein-bound linear DNA

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6
Q

Nucleolus

A

Small spherical region within the nucleoplasm

Manufactures ribosomal RNA and assembles proteins

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7
Q

Nucleus function

A

Controls the cell’s activities

Produces mRNA and tRNA

Retain genetic material as DNA and chromosomes

Manufactures ribosomal RNA and ribosomes

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8
Q

Mitochondrion structure

A

Rod shaped

1-10µm in length

Has a double membrane that controls the entry and exit of materials

Cristae

Matrix

High in cells that have a high level of metabolic activity

Abundant in muscle and epithelial cells for aerobic respiration and active transport

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9
Q

Cristae

A

Extensions of the inner membrane

Provide a large surface area for the attachment of enzymes and other proteins involved in respiration

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10
Q

Matrix

A

Contains proteins, lipids, ribosomes and DNA

Can control the production of some of their own proteins

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11
Q

Mitochondrion function

A

Site for the aerobic stages of respiration

  • The krebs cycle

-Oxidative phosphorylation pathway

Responsible for the production of ATP energy

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12
Q

Endoplasmic reticulum structure

A

Elaborate three dimensional system of sheet-like membranes

Spread through cytoplasm and outer membrane

Network of tubules and flattened sacs called cisternae enclosed in the membrane

Abundant in liver and secretory cells, e.g. epithelial cells have very extensive E.R.

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13
Q

Rough endoplasmic reticulum (RER)

A

Ribosomes present on the outer surface

Large surface area present for the synthesis of proteins and glycoproteins

Provides a pathway for transport of materials

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14
Q

Smooth endoplasmic reticulum (SER)

A

Lacks ribosome

More tubular appearance

Synthesise, store and transport lipids

Synthesise, store and transport carbohydrates

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15
Q

Difference between the RER and SER

A

RER has ribosomes present of surface

SER lacks ribosomes

SER is more tubular

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16
Q

Ribosome structure

A

Small cytoplasmic granules

2 sub units - one small, one large

80s and 70s

Contain ribosomal RNA and a protein

Accounts for up to 25% of the dry mass of a cell

May occur in the cytoplasm or be associated with the RER

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17
Q

80s ribosome

A

Found in eukaryotic cells

25nm in diameter

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18
Q

70s ribosome

A

Found in prokaryotic cells, mitochondria and chloroplasts

Slightly smaller than 80s

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19
Q

Ribosome function

A

Site for proteinsynthesis

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20
Q

Golgi apparatus structure

A

Similar structure to the SER but more compact

Stack of membranes that make up cisternae with vesicles

Abundant in secretory cells such as epithelial cells

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21
Q

Golgi apparatus function

A

Adds carbohydrate to proteins to form glycoproteins and ‘labels’ them

Produce secretory enzymes

Secretes carbohydrates

Transport, modify and store lipids in golgi vesicles

Passes proteins and lipids formed by the ER through a strict sequence

Form lysosomes

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22
Q

Lysosome structure

A

Up to 1µm in diameter

As many as 50 enzymes can be contained in one lysosome

Contain enzymes such as proteases and lipases and lysozymes

Abundant in secretory cells such as epithelial cells and phagocytic cells

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23
Q

Lysosome function

A

Hydrolyse material ingested by phagocytic cells

Release enzymes to the outside of the cell (exocytosis) or into a phagocytic vesicle in order to destroy material around the cell

Digest worn out organelles so useful chemicals can be reused

Completely break down cells after they have died (autolysis)

24
Q

Chloroplast structure

A

Disk-shaped

2-10 mm long and 1 mm in diameter

Chloroplast envelope

Grana

Stroma

Contains both DNA and ribosomes so they can quickly and easily manufacture proteins for photosynthesis

25
The chloroplast envelope
Double plasma membrane Highly selective
26
Grana
Stacks of up to 100 disk-like structures called thylakoids Chlorophyll is found in thylakoids Some thylakoids have tubular extensions that join up with thylakoids in adjacent grana Where the first stage of photosynthesis occurs (light absorption) Granal membranes provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes
27
Stroma
Fluid filled matrix Where the second stage of photosynthesis occurs (synthesis of sugars) Possesses all of the enzymes needed to make sugars
28
Chloroplast function
Carry out photosynthesis
29
Cell wall structure
Consist of microfibrils of cellulose, embedded in a matrix Consist of a number of polysaccharides such as cellulose Thin layer present called the middle lamella which marks the boundary between adjacent cell walls and cements adjacent cells together
30
Cell wall function
To provide mechanical strength to prevent cell from bursting due to pressure from osmosis To give mechanical strength to the plant as a whole To allow water to pass along it and contribute to the movement of water through the plant
31
Cell wall in algae
Made of cellulose and/or glycoproteins
32
Cell wall in fungi
Dont contain cellulose but a mixture of a polysaccharide called chitin, glycan and glycoproteins
33
Vacuole structure
Fluid filled sac Bound by a single membrane called the tonoplast Sac contains mineral salts, sugars, amino acids and pigments such as anthocyanins
34
Vacuole function
Supports herbaceous/herbaceous parts of woody plants Makes cells turgid The pigments attract pollinating insects Sugars and amino acids act as temporary food sources
35
Are animals multicellular or unicellular?
Multicellular
36
Are plants multicellular or unicellular?
Both
37
Are fungi multicellular or unicellular?
Both (e.g. yeast is unicellular)
38
Are protists multicellular or unicellular?
Unicellular
39
What are the 3 domains?
Eukarya Bacteria Archaea
40
Eukarya (structure)
Membrane bound organelles Membrances contain fatty acid chains attached to glycerol via ester bonds Some have cell walls All have 80s ribosomes
41
Bacteria (structure)
No membrane-bound organelles Generally unicellular, but xan be clusters 70s ribosomes Cell walls made of murein, not chitin or cellulose
42
Archaea (structure)
Originally classed as bacteria but they are more complex Membrances similar to eukarya Complex form of RNA polymerase Some have cell walls
43
Prokaryotic cell structure
No nucleus Circular, free flowing DNA No membrane bound organelles Smaller cells 70s ribosomes Plasmids Flagella
44
Eukaryotic cell structure
Distinct nucleus Nuclear envelope Double membrane bound organelles Larger cells 80s ribosomes RER SER
45
Life cycle of a virus
1. Binding - Attachment protein binds onto complementary receptor on the cell 2. Fusion - Lipid envelope/cell membrane fuse together, releasing capsid into cytoplasm 3. Reverse transcription - RNA is converted into DNA 4. Intergration - Viral DNA inserted into host DNA 5. Replication - Use DNA to make parts of virus DNA 6. Assembly - Viruses are assembled 7. Budding - Virus leaves cell and binds onto another receptor and spreads
46
Every virus has
Genetic material Capsid Attachment protein (for movement)
47
Some viruses have
Lipid envelope
48
Membrane structure
Flexible Mainly made of phospholipids
49
Membrane function
Allow cellular compartments to have different conditions
50
Phospholipid bi-layer structure
Hydrophyllic head: Phosphate group Phosphoester bond Hydrophobic tail: Glycerol Ester bond Fatty acid O O O O O || || || || ||Hydophobic tails facing || || || || ||away from water O O O O O
51
Phospholipid behaviour
Form micelles when submerged in water Protein can move freely through the lipid bi-layer
52
Cell fractionation
The process where cells are broken up and the different organelles they contain are separated out
53
The two stages of cell fractionation
Homogenation Ultracentrifugation
54
Conditions before cell fractionation can begin
Tissue is placed in a cold buffered isoptopic solution
55
Why does the solution have to be cold?
To reduce enzyme activity that might break down the organelles
56
Why does the solution have to be buffered?
So the pH does not fluctuate Any change in pH could alter the structure of the organelles or affect the functioning of enzymes
57
Why does the solution have to be isotopic?
To prevent organelles from shrinking or bursting as a result of osmotic loss or gain of water

AQA Biology A level (1 decks)

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