3-Cell Structure

Question 1

Magnification=

Answer 1

Size of image / Size of real object

Question 2

Object

Answer 2

Specimen put under a microscope

Question 3

Image

Answer 3

Specimen when viewed through a microscope

Question 4

Resolution

Answer 4

The minimum distance apart that 2 objects can be in order for them to appear as separate items. Around 0.2 micrometers in a light microscope. Around 0.1 nanometer in an electron microscope.

Question 5

Cell Fractionation

Answer 5

The process where cells are broken up and their organelles are separated out. Solution has to be the same water potential as the tissue to stop organelles bursting/shrinking, cold to reduce enzyme activity, and buffered so pH doesn’t fluctuate. Has 2 stages: Homogenation and Ultracentrifugation.

Question 6

Homogenation

Answer 6

Cells broken up by a homogeniser (blender) to release organelles from cells. Resulting solution is called the Homogenate and is filtered to remove any complete cells/large pieces of debris.

Question 7

Ultracentrifugation

Answer 7

1) Filtrate spun at a low speed in a centrifuge.
2) Heaviest organelles are forced to the bottom to form a thin sediment.
3) Fluid at the top (Supernatant) is removed to leave sediment.
4) Supernatant is transferred to a different tube and spun in the centrifuge at a faster speed than before.
5) The next heaviest organelles are forced to the bottom.
6) Process is repeated to separate out the heaviest organelle as sediment.

Question 8

Transmission Electron Microscope (TEM)

Answer 8

Produces an image by passing an electron beam through a specimen.
Resolving power of 0.1nm

Question 9

Limitations of TEM

Answer 9

System has to be in a vacuum or specimen can’t be observed.
Complex staining process is required.
Specimen has to be extremely thin.
Can only be seen as black or white.

Question 10

Scanning Electron Microscope (SEM)

Answer 10

Reflects an electron beam off of the specimen to get a 3D shape.
Resolving power of 20nm.

Question 11

Limitations of SEM

Answer 11

System has to be in a vacuum or specimen can’t be observed.

Complex staining process is required.

Question 12

Eukaryotic Cells

Answer 12

Cells that are large and have a distinct nucleus and membrane bound organelles.

Question 13

Structure of Nucleus

Answer 13

Spherical and between 10-20 micrometers in diameter and consists of a number of parts:

NUCLEAR ENVELOPE~ Double membrane that surrounds the nucleus which controls entry and exit of materials in and out of nucleus.
NUCLEAR PORES~ Allow passage of large molecules (mRNA). There are around 3000 pores around the nucleus and each are 40-100nm diameter.
NUCLEOPLASM~ Granular, jelly-like material the make sup the bulk of the nucleus.
CHROMOSOMES~ Protein bound linear DNA.
NUCLEOLUS~ Small spherical region within nucleoplasm that manufactures ribosomal RNA and assembles ribosomes. Can be more than 1 in a nucleus.

Question 14

Function of Nucleus

Answer 14

Produce mRNA and tRNA for protein synthesis.
Retain genetic material of the cell as DNA in the form of chromosome.
Manufacture ribosomal RNA and ribosomes.

Question 15

Structure of Mitochondria

Answer 15

Rod shaped and 1-10 micrometers long. Have these parts:

DOUBLE MEMBRANE~ To control entry/exit of material.
CRISTAE~ Extensions of inner membrane and provide large surface are for attachment of enzymes and other proteins in respiration.
MATRIX~ The rest of the mitochondrion which contains proteins, lipids, ribosomes and DNA.

Question 16

Function of Mitochondria

Answer 16

The sites of aerobic respiration.

Responsible for the production of ATP.

Question 17

Structure of Chloroplasts

Answer 17

Disc shaped and 2-10 micrometers long and 1 micrometer in diameter.

CHLOROPLAST ENVELOPE~ Double plasma membrane which selects what enters/exits.
GRANA~ Stacks of 100 disc structures called THYLAKOIDS which contain CHLOROPHYLL where photosynthesis takes place.
STROMA~ Fluid filled matrix where the second stage of photosynthesis takes place.

Question 18

Function of Chloroplasts

Answer 18

Carrying out photosynthesis.

Question 19

Rough Endoplasmic Reticulum (RER)

Answer 19

Has ribosomes on its surface.
Provides large surface area for synthesis or proteins/glycoproteins.
Provides pathway for transport of materials (proteins mainly) through cells.

Question 20

Smooth Endoplasmic Reticulum (SER)

Answer 20

No ribosomes on surface and has a tubular appearance.

Synthesises, stores and transports lipids and carbohydrates.

Question 21

Golgi Apparatus

Answer 21

Similar to SER in structure but is more compact.
Adds carbohydrates to proteins to form glycoproteins.
Produces secretory enzymes.
Secretes carbohydrates.
Transports, modify and stores lipids.
Forms lysosomes.

Question 22

Lysosomes Function

Answer 22

Hydrolyse material ingested by phagocytic cells (white blood cells/bacteria).
Release enzymes outside the cell (exocytosis) to break material around the cell.
Digest worn out organelles.
Break down cells after they’ve died (autolysis).

Question 23

Ribosomes

Answer 23

80S are found in eukaryotic cells and are around 25nm diameter.
70S are found in prokaryotic cells/mitochondria/chloroplasts and are slightly smaller.
The site of protein synthesis.

Question 24

Cell Wall

Answer 24

Provides mechanical strength as a whole as well as to prevent cell bursting from pressure of osmotic entry of water.
Allows water to pass along it.

Question 25

Vacuoles

Answer 25

Fluid filled sac bound by a single membrane (tonoplast).
Support herbaceous plants by making cells turgid.
Contain sugar/amino acids that can act as temporary food stores.
Pigments that colour petals can attract pollinating insects.

Question 26

Tissue

Answer 26

A collection of similar cells that perform the same specific function.

Question 27

Organ

Answer 27

A collection of tissues that are coordinated to perform a variety of functions.

Question 28

Organ Systems

Answer 28

A collection of organs that work together to perform particular functions.

Question 29

Prokaryotic Cells

Answer 29

Smaller spiels with no nucleus/ nuclear envelope.

Question 30

Structure of Bacteria

Answer 30

0.1-10 micrometers long.
Muriel cell wall.
Polymer of polysaccharides and peptides.
Capsule made of mucilaginous slime around the cell wall for protection.
Cell surface membrane inside cell wall
70S ribosomes
Food reserves of glycogen granules/oil droplets.
Circular strand of DNA.
Plasmids

Question 31

Structure of Viruses

Answer 31

20-300nm long.
Contain nuclei acids as DNA or RNA enclosed within a protein coat called a capsid.
Surrounded by a lipid envelope.
If there’s no lipid envelope then there are attachment proteins.

Question 32

Mitosis

Answer 32

Cell division that produces 2 daughter cells with the same amount of chromosomes as the parent cell and each other.
Interphase (not actually part of mitosis)
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis (not actually part of mitosis)

Question 33

Meiosis

Answer 33

Cell division that produces 4 daughter cells with half the number of chromosomes as the parent cell.

Question 34

Interphase

Answer 34

DNA is replicated so the 2 copies of DNA are joined at a place called the centromere.

Question 35

Prophase

Answer 35

Chromosomes become visible.

Nuclear envelope breaks down leaving chromosomes free in the cytoplasm of the cell.

Question 36

Metaphase

Answer 36

Chromosomes are pulled along the spindle fibres and arrange themselves on the equator of the cell.

Question 37

Anaphase

Answer 37

Spindle fibres pull the chromatids making up the chromosome apart to opposite ends (poles) of the cell.

Question 38

Telophase

Answer 38

Nuclear envelopes and nucleolus reforms.

Spindle fibres disintegrate.

Question 39

Cytokinesis

Answer 39

Cytoplasm divides to form 2 new cells, identical to the original.

Question 40

Binary Fission (cell division in prokaryotic cells)

Answer 40

1) Circular DNA molecule replicates and both copies attach to cell membrane.
2) Plasmids also replicate.
3) Cell membrane grows between 2 DNA molecules and pinches inward, dividing cytoplasm in two.
4) New cell wall forms between 2 molecules of DNA, dividing original cell into 2 identical daughter cells.

Question 41

Replication of Viruses

Answer 41

1) Attach to host cell with attachment proteins on their surface.
2) Inject nucleic acid into host cell.
3) Host cell’s metabolic processes start producing viral components, nucleic acids, enzymes, and structural proteins which are assembled into new viruses.

Question 42

The Cell Cycle

Answer 42

Takes 24 hours for most mammalian cells, 90% of which is interphase.

1) Interphase takes up majority of cycle and is also called resting phase because no cell division occurs.
2) Nuclear Division where nucleus divides in 2 (mitosis) or 4 (meiosis).
3) Division of Cytoplasm (Cytokinesis) where cytoplasm divides in 2 (mitosis) or 4 (meiosis).

Question 43

Cancer

Answer 43

A group of diseases (around 200) caused by a growth disorder of cells. Causes the formation of tumours (a group of abnormal cells) by uncontrolled growth and division of cells.

Question 44

Malignant Tumour

Answer 44

A tumour that grows rapidly, are less compact and are more likely to be life threatening.

Question 45

Benign Tumour

Answer 45

A tumour that grows slowly, is compact and isn’t likely to be life threatening.

Question 46

Treatment of Cancer

Answer 46

Chemotherapy disrupts the cell cycle by preventing DNA from replicating or inhibiting metaphase by interfering with spindle formation.