M2 Organelles

Question 1

Mitochondria

Answer 1

Surrounded by 2 membranes
Inner layer folds inwards to form cristae which projects into the matrix
Inner membrane coated in enzymes which catalyse the reactions of aerobic respiration to produce ATP

Question 2

Chloroplasts

Answer 2

Surrounded by a double membrane
Filled with stroma (liquid)
Contains stacks of thylakoid membranes called grana
Thylakoid membranes are the sight of photosynthesis

Question 3

Vacuoles

Answer 3

Plant cells only
Membrane called the tonoplast filled with cell sap.
Full of cell sap = turgid

Question 4

Cytoskeleton

Answer 4

Cell shape and stability
Internal framework
Protein fibres that make up the cytoskeleton are actin filaments (helical polymers of protein actin) and microtubules (hollow cylinders of protein tubulin)

Question 5

Undulipodia

Answer 5

Long structure - >10um
One or two per cell
Enable cell to move
Cylinder containing 9+2 microtubules arranged in a circle

Question 6

Cilia

Answer 6

Short structure - <10um
Occur in large numbers
9+2 microtubule arrangement
Rhythmically beat

Question 7

Nucleus

Answer 7

Contains nuclear envelope, nuclear pore, nucleolus, nucleoplasm and chromatin.
Largest organelle in the cell.
Surrounded by a double membrane or envelope.
Envelope is perforated by pores

Question 8

Nucleolus

Answer 8

Densely staining region where rRNA is produced.

Question 9

Centrioles

Answer 9

Outside the nucleus there are 2 centrioles lying at right angles to each other.
Hollow cylinders about 0.4 micro metres long.
Made of bundles of microtubules
Function is to produce mitotic spindle for cell division

Question 10

SER

Answer 10

Continuous with the nuclear envelope but does not have any ribosomes.
Site of lipid synthesis and steroids
About 22nm in diameter

Question 11

RER

Answer 11

Continuous with the nuclear envelope and is encrusted with ribosomes.
Site of protein synthesis.
About 22nm in diameter

Question 12

Golgi

Answer 12

Stack of flattened cisternae
Continuously being formed at one end where vesicles that bud off the ER
At the other end, the sacs give off vesicles allowing the collection, processing and sorting of molecules ready for transport to other parts of the cell.
Allows packaging of molecules for secretion outside the cell.
Some Golgi vesicles are lysosomes

Question 13

Lysosomes

Answer 13

Sacs surrounded by a single membrane
Produced by the Golgi
0.1-.05 micrometres in diameter
Low pH inside and contain hydrolytic digestive enzymes
They are responsible for the breakdown of unwanted organelles and sometimes extra-cellular structures
They are used by white blood cells to digest bacteria after phagocytosis