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AQA Alevel Biology > Cells > Flashcards

Cells Flashcards

(52 cards)

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1
Q

Cell membrane structure

A

phospholipid bilayer with embedded intrinsic and extrinsic proteins

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2
Q

cell membrane function

A

selectively permeable barrier
controls passage of substances in and out the cell
barrier between internal and external cell environment

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3
Q

Nucleus structure

A

nuclear pores, nucleolus, DNA and nuclear envelope

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4
Q

Nucleus function

A

site of transcription and pre-mRNA splicing - mRNA production
site of DNA replication
nucleolus make ribosomes
nuclear pore allows movement of substances to/from cytoplasm

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5
Q

mitochondria structure

A

double membrane with inner membrane folded into cristae
ribosomes in the matrix
small, circular DNA
enzymes in the matrix

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6
Q

mitochondria function

A

site of aerobic respiration
Produces ATP

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7
Q

Chloroplast structure

A

Thylakoid membranes stacked to form grana, linked by lamella
stroma contains enzymes
contains starch granules, small circular DNA and ribosomes

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8
Q

Chloroplast function

A

Chlorophyll absorbs light for photosynthesised to produce organic molecules

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9
Q

organisms containing chloroplasts

A

plants
algae

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10
Q

Golgi apparatus structure

A

fluid-filled, membrane-bound sacs

vesicles at edge

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11
Q

Golgi apparatus function

A

modifies proteins received from RER
packages them into vesicles to transport to cell membrane for exocytosis
makes lysosomes

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12
Q

Lysosome structure

A

type of golgi vesicle containing digestive enzyme

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13
Q

lysosomes function

A

contains digestive enzymes
e.g lysozymes to hydrolyse pathogen/cell waste products

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14
Q

Rough endoplasmic reticulum function

A

site of protein synthesis
fold polypeptides to secondary and tertiary structure
packaging into vesicles to transport to Golgi

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15
Q

smooth endoplasmic reticulum function

A

synthesises and processes lipids

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16
Q

cell wall function

A

provides structural strength, rigidity and support to cell
helps resist osmotic pressures

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17
Q

ribosome structure

A

small and large subunit
made of protein and rRNA
free floating in cytoplasm and bound to RER
70 in prokaryotes, mitochondria and chloroplasts

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18
Q

Ribosome function

A

site of translation in protein synthesis

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19
Q

rough endoplasmic reticulum structure

A

system of membranes with bound ribosomes
continuous with nucleus

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20
Q

smooth endoplasmic reticulum structure

A

system of membrane with no bound ribosomes

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21
Q

cell wall structure

Study These Flashcards
A

in plant, fungal and bacterial cells
plants - made of microfibrils of cellulose
fungi - made of chitin
bacteria - murein

22
Q

cell vacuole structure

Study These Flashcards
A

fluid-filled
surrounded by a single membrane called a tonoplast

23
Q

contrast prokaryotic and eukaryotic cells

Study These Flashcards
A

prokaryotic cells are smaller
prokaryotes have no membrane bound organelles
prokaryotes have smaller ribosomes
prokaryotes have no nucleus-
circular DNA not associated with histones
prokaryotic cell wall made of
murein instead of cellulose/ chitin

24
Q

occasional features of prokaryotes

Study These Flashcards
A

plasmids - loops of DNA
capsule surrounding cell wall - helps agglutination + adds protection
flagella for movement

25
cell vacuole function
makes cells turgid - structural support temporary store of sugars, amino acids coloured pigments attract pollinators
26
protein carriers
Bind with a molecule which causes a change in shape of the protein this change in shape enables the molecule to be released to the other side of the membrane
26
Protein channels
tubes filled with water enabling water-soluble ions to pass through the membrane selective channel proteins only open in the presences of certain ions when they bind to the protein
27
features of viruses
non-living and acellular contain genetic material, capsid and attachment proteins some contain a lipid envelope and enzymes
28
3 types of microscopes
optical scanning electron microscopes transmission electron microscopes
29
magnification
image/actual how many times larger the image is compared to the object
30
resolution
the minimum distance between 2 objects which can still be viewed as separate determined by the wavelength of light
31
optical microscopes
beam of light used to create image glass lens used for focusing 2D coloured image produced
32
Evaluate optical microscopes
poorer resolution as long wavelength of light - small organelles not visible lower magnification can view living samples simple staining method vacuum not required
33
TEM
beam of electrons passes through the sample used to create an image focused using electromagnets 2D, black and white image produced can see internal ultrastructure of cell structures absorb electrons and appear dark
34
evaluation TEMs
Highest resolving power high magnification extremely thin specimens required complex staining method specimen must be dead vacuum required
35
SEM
Beam of electrons pass across sample used to create image focused using electromagnets 3D, black and white image produced electrons scattered across specimen producing image
36
Evaluation SEM
High resolving power high magnification thick specimens usable complex staining method specimen must be dead vacuum required
37
Why calibrate eyepiece graticule?
Calibration of the eyepiece is required each time the objective lens is changed calibrate to work out the distance between each division at that magnification
38
Homogenisation
Process by which cells are broken open so organelles are free to be separated done using homogeniser
38
purpose of cell fractionation
break open cells and remove cell debris so organelles can be studied
39
homogenisation conditions
Cold reduces enzyme activity preventing organelle digestion Isotonic prevents movement of water by osmosis - no bursting / shrivelling of organelles Buffered resists pH changes preventing organelle + enzyme damage
40
Ultra-centrifugation
Homogenate solution filtered to remove cell debris solution placed in a centrifuge which spins at a low speed initially then increasingly faster speeds to separate organelles according to their density
41
Differential centrifugation
supernatant first out is most dense = nuclei spun at higher speeds chloroplasts > mitochondria > lysosomes
42
binary fission
involves circular DNA plasmids replicating cytokinesis creates 2 daughter nuclei each daughter cell has 1 copy of circular DNA and a variable number of plasmids
43
cell cycle
interphase nuclear division - mitosis or meiosis cytokinesis
44
interphase
Longest stage in the cell cycle when DNA replicates (S-phase) and organelles duplicate while cell grows (G1&G2-phase) DNA replicates and appears as two sister chromatids held by centromere
45
mitosis
One round of cell division two diploid, genetically identical daughter cells growth and repair (e.g. clonal expansion) comprised of prophase, metaphase, anaphase and telophase
46
prophase
Chromosomes condense and become visible nuclear envelope disintegrates in animals - centrioles separate & spindle fibre structure form
47
metaphase
Chromosomes align along equator of cell spindle fibres released from poles now attach to centromere and chromatid
48
anaphase
Spindle fibre contracts (using ATP) to pull chromatids, centromere first, towards opposite poles of cell centromere divides in two
49
telophase
Chromosomes at each pole become longer and thinner again spindle fibres disintegrate + nucleus reforms
50
mitotic index
Used to determine proportion of cells undergoing mitosis Calculated as a percentage OR decimal num of cells in mitosis/ total num of cells X100

AQA Alevel Biology (22 decks)

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