sub cellular organelles

Question 1

what are the precursors of lysosomes

Answer 1

• endosomes

Question 2

what enzymes do lysosomes contain

Answer 2

• hydrolytic enzymes coming from the Golgi complex which degrade proteins and other large molecules

Question 3

major job of lysosomes

Answer 3

• eliminate unwanted cellular material and recycle their components
• destroy bacteria and yeast (in immune cell)

Question 4

name 4 digestive enzymes that lysosomes contain

Answer 4

• nucleases - breakdown of DNA/RNA
• phosphatases - removes phosphate
• glycosidases - breakdown of sugar
• proteases - breakdown of protein

Question 5

what does peroxisome do

Answer 5

• degrades long chain fatty acids and cholesterol
• converts cholesterol to bile
• these reactions produce toxic hydrogen peroxide - this is degraded by catalase
• synthesise plasmalogens - which is a component of myelin

Question 6

what three processes do lysosomes process materials brought to the cell by

Answer 6

• phagocytosis
• pinocytosis
• autophagy
• receptor - mediated endocytosis

Question 7

what is autophagy

Answer 7

• self breakdown
• breakdown unwanted cellular components eg organelles
• takes place in autophagosome initially
• then fuses with lysosome
• can be macro or micro autophagy

Question 8

what is p gingivalis

Answer 8

• anaerobic bacteria, which produce proteins called gingipains and cause gum damage

Question 9

where are peroxisomes founds

Answer 9

• in liver cells and are specialised lysosomes

Question 10

how are peroxisomal disorders caused

Answer 10

• caused by mutations in the peroxisomal enzymes
• or faults in peroxisome assembly
• cause toxic long chain fatty acids to accumulate

Question 11

what is the process called when things exit from a cell

Answer 11

• exocytosis

Question 12

what are the two ways things may be secreted

Answer 12

• constitutive secretion
• regulated secretion
• vesicles are sometimes processed through the endosomal pathway

Question 13

explain endosomal pathway

Answer 13

• membranous ‘bubbles’ released by cells
• different classes; exosomes (released from endosomes)
  ; microvesicles (‘bud away’ from plasma membrane)

Question 14

how are extracellular vesicles formed

Answer 14

• exosomes formed through endocytosis
• multi vesicular body
• processed through Golgi body
• cell surface
• vesicles released from the cell and bind or interact with other cells

Question 15

what is the ER connected to and what does it consist of

Answer 15

• the nuclear membrane is connected to the ER
• it is a network of membranous tubules
• consists of smooth and rough ER

Question 16

what is smooth er involved with

Answer 16

• contains enzymes for
  ; lipid synthesis
  ; steroid hormone synthesis
  ; metabolising toxins eg alcohol
• stores calcium and contains no ribosomes

Question 17

what is rough er involved with

Answer 17

• studded with ribosomes
• involved in production and processing of proteins in collaboration with the Golgi complex
• can also modify proteins; initiate adding of carbohydrates and adding membrane anchors

Question 18

how are diseases caused in ER

Answer 18

• usually due to mutation in amino acid sequence causing misfolding
• proteins not processed properly and not taken from ER to Golgi
• diseases caused by proteins being retained in the ER
  ; CF
  ; diabetes

Question 19

function of Golgi apparatus

Answer 19

• proteins synthesised in the rough ER are transported to Golgi complex in vesicles
• modifies the proteins made in the rough ER
• distributes the modified proteins to lysosomes, plasma membrane or secretory vesicles

Question 20

structure of Golgi apparatus

Answer 20

• sack of flattened vesicles with a cis network, facing nucleus
• and a trans network, facing plasma membrane
• proteins are transported to and from Golgi in vesicles

Question 21

vesicles in Golgi

Answer 21

• vesicles are coated in different proteins depending on their destination
• proteins travel from ER to cis face of Golgi in COP11 coated vesicles
• when processed in golgi, proteins travel to membrane in clathrin coated vesicles
• vesicles are recycled - coated in COP 1 and transported back to the ER

Question 22

how is cholera caused

Answer 22

• cholera toxin binds to a component of COP1 and is processed and activated in ER
• the cholera toxin activated the CFTR channel, disrupting Cl- transport in guts
• this causes secretion of water, dehydration and diaheria

Question 23

what does mitochondria do

Answer 23

• power station of cell

- oxidise fuel in their inner matrix and generate ATP across their inner membrane via the ETC

Question 24

what is the purpose of the inner membrane of the mitochondria being folded

Answer 24

• maximises the surface area for generating ATP

- these folds are called cristae

Question 25

how is the mitochondria different from other organelles

Answer 25

• they are able to divide independently and they have its own DNA, which encodes some of the protein required to make new mitochondria
• still require proteins from mitochondria

Question 26

how are mitochondrial diseases caused

Answer 26

• mutation in mitochondrial DNA cause disease
• symptoms are caused by a lack of ATP in affected organs
• particularly affect organs with high energy demand eg. muscles

Question 27

what is mitophagy

Answer 27

• specifically degrades and recycles mitochondria

- known to contribute to development of Parkinson’s and dementia

Question 28

3 features of prokaryotes

Answer 28

• have no membrane bound organelles
• have a nucleoid
• have a peptidoglycan cell wall as a cell membrane
• aerobic bacteria have no mitochondria but generate ATP across cell membrane

Question 29

what are cilia and flagella composed of and purpose

Answer 29

• specialised structure
• structure extends from plasma membrane
• present in multi cellular and uni cellular organelles
• composed of bundles of microfilaments
• used for propelling liquids and other material along surfaces

Question 30

what is cytoskeleton composed of and purpose

Answer 30

• composed of tubules and filaments

- dictates structure and shape of cell

Question 31

what is organelle biogenesis

Answer 31

• new organelles are formed by expansion of existing ones
• the new phospholipids are synthesised in the smooth ER
• move to organelles - in vesicles (golgi, lysosomes) or by transport proteins (mitochondria)
• proteins are synthesised in mitochondria or er