Bevington 3 organelles

Question 1

CYTOSOL STRUCTURE:

Answer 1

• Semi-fluid substance between plasma membrane & nucleus (not including organelles)

Question 2

CYTOPLASM:

Answer 2

Cytosol + organelles

Question 3

MITOCHONDIRA STRUCTURE

Answer 3

•	Evolved: endocytosis of prokaryotes 
=> double lipid bilayer outer & inner (cristae)
•	Creating 2 compartments:
o	Intermembrane space
o	Mitochondrial matrix

Question 4

MITOCHONDIRA FUNCTION

Answer 4

• Mitochondirial matrix: environment for Respiration
• Cristae: provide large SA for membrane-bound enzymes in respiration
• Respiration: Glycolysis (cytosol) produces pyruvate that is converted to ATP (mitochondrial)
• Chemiosmosis = pumps ions across membrane, uses ATP

Question 5

ENDOPLASMIC RETICULUM: STRUCTURE

Answer 5

• Part of endomembrane system
• Creates intermembrane space separate from cytosol
• Continuous w/ nuclear envelope intermembrane space
o Rough ER (ribosomes)
o Smooth ER –
o Transitional ER – to golgi buds off

Question 6

ENDOPLASMIC RETICULUM:
FUNCTIONS
• Rough ER

Answer 6

o Ribosomes dock here to synthesise secretory proteins into lumen => Segregates proteins from cytosol
o Produces more ER membrane

Question 7

ENDOPLASMIC RETICULUM:
FUNCTIONS
• Smooth ER:

Answer 7

o	Synthesizes lipids (bilayer too)
(& other hydrophobic metabolites e.g. cholesterol & steroids)
o	Metabolizes carbohydrates
o	Detoxifies poisons (like alcohol…)
o	Stores calcium in the lumen)

Question 8

ENDOPLASMIC RETICULUM:
FUNCTIONS
• Transitional ER:

Answer 8

where vesicles depart to Golgi

Question 9

GOLGI APPARATUS: STRUCTURE

Answer 9

• Flattened membranous sacs = cisternae
o Unlike ER, separate cisternae NOT connected to each other
o Structure & enzyme content change from cis to trans

Question 10

GOLGI APPARATUS:

FUNCTION

Answer 10

• Modifies products of rough ER =>carbohydrate side chains on glycoproteins
• Manufactures some macromolecules : E.g. pectins & polysaccharides

Question 11

2 competing hypotheses about how substances move through the Golgi:

Answer 11

o Vesicular transport
o Cisternal maturation (currently accepted explanation)
• Transit time through the Golgi: 10 min

Question 12

Protein synthesis transport process

Answer 12

1 Nuclear envelope => rough ER => smooth ER
=>Membranes & proteins produced by ER flow by of transport vesicles
=> Golgi => pinches off transport vesicles & other vesicles
=> lysosomes & vacuoles
=> fusion w/ another vesicle for digestion
=> carries proteins to plasma membrane for secretion
=> expands by fusion of vesicles
=> proteins secreted from cell

Question 13

BIOCHEMICAL REACTIONS IN COMPARTMENTS

Answer 13

Some enzymes (and the reactions that they catalyse) may be incompatible, requiring for example different conditions of pH, Ca2+ concentration or oxidising or reducing conditions

Question 14

MAMMALIAN CELL:

compartmentalisation

Answer 14

Endosomal compartment, lysosomes & secretory vesicles =pH 5 to 6 nM?
SER: Oxidising to drive oxidations involved in synthesis & de- toxification

Cytosol = pH 7.1 resting 10-100nM Ca2+ Relatively reducing conditions

Extracellular fluid = pH 7.4 2nM Ca2+

Mitochondrial Matrix = pH 7.6 mM? Oxidising to drive electron transport & oxidative phosphorylation

Peroxisomes – Strongly oxidising to drive e.g b-oxidation of fatty acids

Question 15

CYTOSOL & MITOCHONDIA COMPATMENTATION

Answer 15

-Use ATP as a probe of sub-cellular compartmentation

Question 16

Sodium Potassium ATPase

Answer 16

ONLY uses ATP generated by enzymes of glycolsis NOT ATP released into cytosol by mitochondria

Question 17

Proteasomes:

Answer 17

multi-sub-unit complexes of globular proteins & protease enzymes (degrade proteins)

Question 18

Glycolytic enzymes:

Answer 18

associating w/ plasma membrane integral proteins

Question 19

PLANTS COMPARTMENTATION

Answer 19

e.g. Plants producing poisons to protect themselves from herbivores
- CN- substitutes for O2 (binding to cytochrome oxidase in inner membrane) and blocks electron transport and ATP synthesis
=> Compartmentation of poisons in vacuole= cyanogenic glycosides
Cytosol= beta – glycosidase in

Question 20

PROKARYOTE COMAPRTMENTATION: ENDOSPORES

Answer 20

specialised form of cell division – not strictly organelle formation
=> highly resistant to destruction = pathological

= opportunity for bio-terrorism