the eukaryotic cell part 2

Question 1

what are lysosomes

Answer 1

organelles found in animal cells which contain digestive enzymes and are responsible for degrading worn out or obsolete components of the cell, as well as destroying invading bacteria and programmed cell death

Question 2

what are the three primary transport routes to the lysosomes

Answer 2

1) endocytosis
2) phagocytosis
3) autophagy

Question 3

what is endocytosis

Answer 3

invaginations of the cell membrane form vesicles that bud off and transport objects through the cell to the lysosome

Question 4

what is phagocytosis

Answer 4

a form of endocytosis where whole cells and other large insoluble particles move from the cell surface to the lysosomes

Question 5

what is autophagy

Answer 5

where worn out organelles and bulk cytoplasm are surrounded by a membrane and delivered to the lysosomes

Question 6

what happens in the lysosome

Answer 6

the lumen of the lysosome is acidic and contains hydrolytic enzymes which degrade polymers into their monomeric subunits
- pump H+ and Cl- ions from the cytosol across the membrane acidifying the lumen

Question 7

what enzymes are included in the lysosome

Answer 7

1) nucleases- degrade RNA and DNA
2) proteases- degrade proteins and peptides
3) phosphatases - remove phosphate groups

Question 8

what are primary lysosomes

Answer 8

roughly spherical and do not contain obvious particulate or membrane debris
it is formed by the fusion of the Golgi vesicles with late endosomes

Question 9

what are secondary lysosomes

Answer 9

larger and more irregular shaped, result from fusion of primary lysosomes with other membrane bound organelles and vesicles

Question 10

what are residual bodies

Answer 10

where indigestible materials pass outwardly and fuse with the plasma membrane

Question 11

what are autophagic vacuoles

Answer 11

a fusion of a primary lysosome with a autophagosome

Question 12

what are the main types of vacuole

Answer 12

1) storage
2) lytic

Question 13

what is a storage vacuole

Answer 13

where the vacuole membrane contains a variety of transport proteins which allow plant cells to accumulate and store water, ions and nutrients

Question 14

what is a lytic vacuole

Answer 14

the lumen of a vacuole has an acidic PH and contains degradative enzymes

Question 15

how does the vacuole keep its shape

Answer 15

the membrane is permable to water but not to small molecules stored within it. the solute conc therefore is much higher inside than outside so water moves into the vacuole by osmosis which increases turgor

Question 16

what is a peroxiosome

Answer 16

organelles which play a key role in lipid metabolism and control of reactive oxygen species
in the liver and kidney cells they degrade toxic molecules.
THEY OXIDISE ORGANIC SUBSTANCES LIKE FATTY ACIDS AND AMINOACIDS

Question 17

what is the endoplasmic reticulum

Answer 17

an extensive network of closed, flattened membrane bound sacs called cisternae which is important in the synthesis of lipids, membrane proteins and secreted proteins

Question 18

what are the two regions the ER is divided into

Answer 18

1) smooth which lacks ribosomes
2) rough which is studded with ribosomes

Question 19

what is the smooth ER

Answer 19

a subset of the endomembrane system which synthesises lipids, fatty acids, phospholipids, steroid hormones and involved in the detoxification of harmful metabolic by-products

Question 20

what do enzymes in the SER do in the liver

Answer 20

modify or detoxify hydrophobic chemicals by chemically converting them into water soluble products that can be excreted from the body

Question 21

what does the RER do

Answer 21

synthesis of proteins

Question 22

outline how proteins are transported from the ER to their destination

Answer 22

1) membranes and secreted proteins have signal sequences
2) signal sequences direct ribosomes to the ER membrane where they dock on the transposon protein complex
3) polypeptide synthesis starts and the signal peptide is cleaved
4) completed polypeptides leave the ribosomes and folds into final conformation

Question 23

what is the golgi complex

Answer 23

the main sorting hub of the secretory pathway which recives proteins and membrane lipids first synthesised in the ER.
it completes the chemical modifications and then packages and transports to appropriate destinations

Question 24

outline the structure of the golgi complex

Answer 24

a series of flattened membrane vesicles or sacs surrounded by a number of spherical vesicles

Question 25

what are the three defined regions

Answer 25

1) the cis region which accepts things from the ER
2) the medical region where final modifications are done
3) the trans medium where everything is sorted and sent off

Question 26

outline transport through the golgi complex

Answer 26

1) vesicles from the RER fuse with the cis membranes of the golgi complex
2) proteins in the vesicles move to the cis region to the medial region and finally to the trans region
3) vesicles bud off the trans golgi membranes
4) vesicles containing proteins move to the cell surface and others move to the lysosome

Question 27

what are the major sites of protein sorting in cells

Answer 27

ER
golgi complex
vesicles

Question 28

outline the secretory pathway

Answer 28

1) transport vesicles bud off and carry secreted proteins to the golgi complex
2) proteins are concentrated and packaged into immature secretory vesicles
3) vesicles then coalesce to form larger mature secretory vesicles
4) they accumulate under the apical surface of the cell and fuse with membrane releasing content

Question 29

what happens to proteins lacking the ER signal sequence in non-secretory pathways

Answer 29

1) released into the cytosol and remain their
2) proteins with organelle specific targeting sequence first released into the cytosl but then imported into other organelles