Hettema (Autumn - Structure of eukaryotic cells and different cytoplasmic structures)

Question 1

What is the problem to euks of having large cells, and how is this solved?

Answer 1

• low SA:vol –> flattened cells, microvilli

- need to keep conc reactants sufficiently high –> compartmentalisation of cellular functions

Question 2

What is the cytoplasm?

Answer 2

• viscous contents of cell contained w/in plasma membrane, excluding nucleus

Question 3

What is the cytosol?

Answer 3

• unstructured aq phase of cyto, excluding organelles, membranes and insoluble material (cytoskeleton)

Question 4

What are the functions of the plasma membrane?

Answer 4

• encloses contents and provides barrier
• reg movement in and out cell
• helps maintain cell shape
• communication w/ other cells and extracellular env
• attachment to extracellular structures
• certain biochem reactions only occur at plasma membrane

Question 5

What does the nucleus contain?

Answer 5

• chromosomes
• nucleolus
• nuclear pores

Question 6

What is the structure and role of the nucleolus?

Answer 6

• granular body of RNA and protein

- site of rRNA synthesis and ribosome subunit assembly

Question 7

What are the 2 major pathways of the endomembrane system, and what organelles do they involve?

Answer 7

• endocytic pathway –> endosomes, lysosomes, autophages, phagosomes
• secretory pathway –> ER, golgi, secretory vesicles

Question 8

What happens during the endocytic pathway?

Answer 8

• uptake of small macromolecules by endocytosis
• uptake of particles from outside cells by phagocytosis
• degradation of aged organelles by lysosomes (autophagy)

Question 9

What is the role of the endocytic pathway?

Answer 9

• directs material to lysosomes

Question 10

What is the structure and function of endosomes?

Answer 10

• bound by single membrane
• shape varies
• v important in sorting proteins for degradation and reuse

Question 11

What is the structure and role of lysosomes?

Answer 11

• digesting bodies
• v e- dense
• single membrane
• heterogenous morphology
• high contents of hydrolytic enzymes (for breakdown of polymers at low pH - acid hydrolases)

Question 12

What is the role of the secretory pathway?

Answer 12

• transport between series of compartments

Question 13

What are the differences between the RER and SER?

Answer 13

• RER = w/ ribosomes, synthesis of many proteins destined for secretion and incorporation into membrane
• SER = w/o ribosomes, lipid biosynthesis, mod hydrophobic chemicals to make more water soluble (drug detox)

Question 14

What is the structure and role of the golgi?

Answer 14

• stack of flattened vesicles
• processing and packaging of secretory and membrane proteins
• sorting of proteins for various destinations in cell

Question 15

What is the structure and role of mitochondria?

Answer 15

• elongated structures
• form connections w/ each other
• 2 lipid bilayer
• site of most cellular rep reactions
• contain own genome, replication machinery, ribosomes

Question 16

What is the structure and role of peroxisomes?

Answer 16

• contain catalase
• single membrane
• small spheres
• low abundance
• freq crystalline core
• H2O2 prod ox of FAs and variety of other substrates

Question 17

What does catalase do?

Answer 17

• reducing enzyme

- degrades H2O2 –> H2O + O2

Question 18

What does a typical plant cell have, which animal cells do not?

Answer 18

• vacuole
• cell wall
• chloroplast

Question 19

What is the role of a vacuole?

Answer 19

• storage of small molecules
• lysosome like activities
• turgor pressure

Question 20

What is the structure and role of cell wall?

Answer 20

• consists of cellulose myofibrils
• v rigid structure when finished
• acts against turgor to prevent bursting

Question 21

What is the role of plasmodesmata?

Answer 21

• connect neighbouring plant cells

Question 22

What is the structure and role of chloroplasts?

Answer 22

• type of plastid
• large
• similar structure to mito, but w/ extra internal membrane system = thylakoids
• contain own genome, replication machinery, ribosomes

Question 23

What is the role of the cytoskeleton?

Answer 23

• provides stability and movement

- for movement of cells themselves or intracellular movement of bacteria

Question 24

What are the steps in movement of cells by the cytoskeleton?

Answer 24

• protrusion of leading edge
• adhesion at leading edge
• deadhesion at trailing edge
• movement of cell body