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A-level Biology > B3 Cell Structure > Flashcards

B3 Cell Structure Flashcards

1
Q

Function of nucleus

A

Site of DNA replication and transcription (making mRNA)

Contains genetic code for each cell

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2
Q

Structure of nucleus

A

Nuclear Envelope- double membrane

Nuclear Pores

Nucleoplasm - granular, jelly-like material

Chromosomes -protein-bound, linear
DNA

Nucleolus - smaller sphere inside which is the site of RNA production and makes ribosomes.

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3
Q

Function of endoplasmic reticulum

A

RER - Protein Synthesis

SER - Synthesis and store lipids and carbohydrates

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4
Q

Structure of endoplasmic reticulum

A

Rough and smooth ER have folded membranes called cisternae

Rough have ribosomes on cisternae

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5
Q

Function of Golgi apparatus and vesicles

A

Add carbohydrates to proteins to form glycoproteins

• Produce secretory enzymes

Secrete carbohydrates

Transport, modify and store lipids

• Form lysosomes

Molecules are ‘labelled’ with their destination

Finished products are transported to cell surface in Golgi vesicles where they fuse with the membrane and the contents in released.

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6
Q

Structure of Golgi apparatus and vesicles

A

Folded membranes making cisternae

Secretary vesicles pinch off from the cisternae

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7
Q

Function of lysosomes

A

Hydrolyse phagocytic cells

• Completely break down dead cells (autolysis)

• Exocytosis - release enzymes to outside of cell to destroy material

• Digest worn out organelles for reuse of materials

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8
Q

Structure of lysosomes

A

Bags of digestive enzymes - can contain 50 different enzymes.

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9
Q

Structure of mitochondria

A

Double membrane

Inner membrane called the cristae

Fluid centre called the mitochondrial matrix

Loop of mitochondria DNA

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10
Q

Function of mitochondria

A

• Site of aerobic respiration

Site of ATP production

• DNA to code for enzymes needed in respiration

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11
Q

Structure of ribosomes

A

Small, made up of two sub-units of protein and rRNA

80s- large ribosome found it eukaryotic cells (25nm)

70S - smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts.

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12
Q

Function of ribosomes

A

Site of protein synthesis

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13
Q

Structure of vacuole

A

Filled with fluid surrounded by a single membrane called a tonoplast

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14
Q

Function of vacuole

A

Make cells turgid and therefore provide support

• Temporary store of sugars and amino acids

• The pigments may colour petals to attract pollinators.

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15
Q

Function of chloroplasts

A

Site of photosynthesis

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16
Q

Structure of chloroplasts

A

Surrounded by a double membrane

Contains thylakoids (folded membranes embedded with pigment)

Fluid filled stroma contains enzymes for photosynthesis

Found in plants

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17
Q

Function of cell wall

A

Provide structural strength to cell

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18
Q

Structure of cell wall

A

In plant and fungi cells

Plants- made of microfibrils of the cellulose polymer.

Fungi - made of chitin, a nitrogen-containing polysaccharide

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19
Q

Function of plasma membrane

A

Controls entrance and exit of molecules

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20
Q

Structure of plasma membrane

A

Found in all cells

Phospholipid bilayer - molecules embed within and attached on the outside (proteins, carbohydrates, cholesterol)

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21
Q

Calc mitotic index

A

Count how many cells are visible in filed of view and number of cells visible that are in stage of mitosis

Mitotic index = (number of cells in mitosis / total number of cells) x 100

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22
Q

What are the 4 stages of mitosis

A

Prophase

Metaphase

Anaphase

Telophase

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23
Q

Info about mitosis

A

1 round of division

Genetically identical cells are made

Diploid cells are made

Growth and repair

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24
Q

What happens in prophase

A

Chromosomes condense + become visible

Centrioles separate + move to opp ends of poles of cell

Nucleolus disappears

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25
What happens in anaphase
Spindle fibres start to retract + pull centromere and chromatids they’re bound to towards opp poles Centromere divide in 2 Individual chromatids are pulled to each opp pole (chromatids now referred to as chromosomes) Requires energy in form of atp - provided by respiration in mitochondria
26
What happens in metaphase
Chromosomes align along equator Spindle fibres released from poles now attach to centromere and chromatid
27
What happens in telophase
Chromosomes at each pole become longer + thinner again Spindle fibres disintegrate, nucleus starts to reform Nuclear membrane reforms Nucleoli reappear Cytoplasm splits in 2 to create 2 new genetically identical cells
28
What are the 3 stages of cell cycle
Interphase (G1, S, G2) Nucelar division (mitosis + meiosis) Cytokinesis
29
What is interphase
Longest stage in cell cycle When organelles double, cell grows and DNA replicates
30
How do prokaryotic cells replicate
Binary fission and viruses don’t undergo cell division as they’re non-living Viruses replicate inside of host cells they invade by injecting their nuclei acid into cell to replicate virus particles.
31
What are 3 types of microscopes
Optical (light) microscopes Transmission electron microscopes Scanning electron microscopes
32
Define magnification
how many times larger the image is compared to the object.
33
Define resolution
the minimum distant between two objects in which they can still be viewed as separate.
34
Optical (light) microscope
Light Beam condensed to create image Poor resolution - light have longer wavelength Low magnification Coloured images Can view living samples
35
Electron microscope (scanning or transmission)
Electron beam condensed to create image Electromagnets used to condense beam High resolution - electrons have short wavelength High magnification Black and white images Sample must be in vacuum + non-living
36
Are small organelles visible in light microscope
No because of poor resolution of microscope - long wavelength of light
37
Why must Samples be in vacuum in Electron microscope
As Electrons are absorbed by air
38
Why must Samples be stained in Electron microscope
The image is in black and white
39
How is an image produced in TEM
Extremely thin specimen stained and place in vacuum Electron gun produces electron beam that passes through specimen Some parts absorb electrons and appear dark Image produced is 2d - shows detailed images on internal structure of cells
40
How is an image produced in SEM
The specimens do not need to be thin, as the electrons are not transmitting through. Instead, electrons beamed onto surface and electrons are scattered in diff ways depending on contours. This produces a 3D image.
41
Magnification equation
Magnification = image size / actual size
42
Converting units
M - mm - micrometre - nm ——> x1000 <—— divide by 1000
43
What is cell fractionation used for
To isolate diff organelles so they can be studied This enable individual organelle structures and functions to be studied
44
What happens in cell fractionation 1st
Cells are broken open to release contents and organelles are then separated
45
Why must cells be prepared in cold, isotonic, and buffered solution
Cold: To reduce enzyme activity. When cell is broken open enzymes are released which could damage organelles Isotonic: organelles must be same water potential as solution to prevent osmosis, as this could cause organelles to shrivel / burst. Buffered: solution has pH buffer to prevent damage to organelles
46
What are the 2 main steps in cell fractionation
Step 1 = homogenisation Step 2 = ultracentrifugation
47
What happens in step 1 of cell fractionation
cells must be broken open (homogenised) and this is done using blender. cells are blended in cold, isotonic and buffered solution.
48
What happens in step 2 of cell fractionation
filtered solution is spun at high speed in centrifuge. This separates organelles according to their density.
49
The order of organelle fractionation
1st : (slowest speed 1st) Nuclei Chloroplasts Mitochondria Lysosomes Endoplasmic reticulum Ribosomes Last:(fastest speed)
50
How does the centrifuge separate the pellets
centrifuge spins at high speeds and centrifugal forces causes pellets of most dense organelle to form at bottom of tube. process repeated at increasingly faster speeds, removing supernatant each time (liquid) leaving behind pellet ( isolated organelle). supernatant is then spun again in centrifuge and process is repeated.
51
Suggest and explain the function of enzyme ATP hydrolase in absorbing amino acids.
1.Hydrolysing ATP into ADP + Pi releases energy 2. This energy actively transports sodium ions out of the epithelial cells into the blood 3. This creates a sodium ion concentration gradient from the ileum into the epithelial cells 4. Sodium ions are cotransported into the epithelial cells with amino acids
52
(Mitosis practical) explain why the student used the 1st 5mm from onion root tip
This is where mitosis occurs
53
(Mitosis practical) explain why the student pressed down on the cover slip firmly
To create a single layer of cells so that light can pass through the specimen
54
(Mitosis practical) explain why the student added acid to the root
To break down links between cells/cell walls
55
Describe how HIV replicates inside of helper T cells.
1. RNA is converted into DNA using the enzyme reverse transcriptase 2. The DNA is inserted into the DNA of the helper T cell 3. The DNA is transcribed into mRNA 4. This HIV mRNA is then translated into HIV proteins to make a new viral particles
56
Function of the flagella in prokaryotic cell
Flagella rotates to enable bacteria to move
57
What is the capsule made of and its function
A slimy layer made of protein This prevents the bacteria from desiccating (drying out) and protects the bacteria against the host's immune system.
58
What are plasmids
small loops of DNA which only carry a few genes.
59
What is the cell wall like in prokaryotic cell
Contains murein (a glycoprotein)
60
What is the cell wall like in eukaryotic cell
In plant and fungi cells Plants- made of microfibrils of the cellulose polymer. Fungi - made of chitin, a nitrogen-containing polysaccharide
61
Structure of nucleus in prokaryotic cell
No nucleus - Instead of a nucleus there is a single circular DNA molecule free in the cytoplasm which is not protein bound.
62
What don’t prokaryotic cells contain
Membrane bound organelles E.g. mitochondria, chloroplasts, endoplasmic reticulum, Golgi, nucleus
63
What are the Key differences between prokaryotic cells and eukaryotic cells and what might prokaryotic cells also contain
The cells are much smaller. No membrane bound-organelles Smaller ribosomes No nucleus A cell wall made of murein They may also contain: Plasmids A capsule around the cell Flagella

A-level Biology (21 decks)

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