Lecture 6

Question 1

Lysosomes

Answer 1

• Like the cells stomach (acidic- pH 4.5 breaks things down)

-it’s enzymes only function at acidic pH so great examples of Compartmentalization

• hydrolyses both internal and external stuff
  
  • internal: organelles that are old/not functioning correctly (autophagy)
    *external: bacteria and debris engulfed by phagocytosis
• not present in plants (they use lytic vacuoles)

Question 2

Vacuoles

Answer 2

-Present in plants and fungi

-filled with fluid

-Some protein/ also have specialized vacuoles called contractile vacuoles that pomp excess water out of the cell

Question 3

Vacuole function

Answer 3

• turgid pressure for cell enlargement
• storage of nutrients
• digest waste products (similar to lysosomes)
• pigmentation

Question 4

Nuclear envelope quick

Answer 4

Control in/out of nucleus

Question 5

Rough ER quick

Answer 5

Protein synthesis/ folding

Question 6

Smooth ER quick

Answer 6

Lipid synthesis / detox

Question 7

Golgi quick

Answer 7

Protein modification and sorting into vesicles

Question 8

Vesicles quick

Answer 8

Carry thing between compartments

Question 9

Lysosomes quick

Answer 9

Stomach of the cell

Question 10

Vacuoles quick

Answer 10

Turgid pressure and other diverse roles

Question 11

Plasma membrane quick

Answer 11

Surround cell, control in/out

Question 12

Semi-autonomous organelles why aren’t they part of Endomembrane system

Answer 12

Although surrounded by membranes, they aren’t part of Endomembrane system bc they don’t send or receive vesicles

Question 13

Semi autonomous organelles example

Answer 13

Mitochondria
Chloroplasts

Question 14

What do mitochondria and chloroplasts have in common

Answer 14

Involved in generation of bioenergy

Both use electrochemical reactions to make energy

Both have internal membranes with extensive folding to increase the surface area of the energy producing machinery

Question 15

How does mitochondria converts into energy

Answer 15

Sugars > respiration > ATP

Question 16

How do chloroplasts make energy

Answer 16

CO2 > photosynthesis > sugars

Question 17

Why semi autonomous

Answer 17

• Each arose from ancient prokaryotic symbionts that gradually evolved to rely on host cell and can’t live independently anymore
• each have their own genome (small. Circular. Like plasmids)
  
  • most of the genes were lost or transferred to the host
• have own ribosomes and make proteins
  
  • but most proteins come from host cell

-replicate on their own by division
* uses essentially same division machinery as modern prokaryotes

-have double membranes like modern prokaryotes

-have similar shapes and sizes as modern prokaryotes

Question 18

Mitochondria

Answer 18

• the source of all cellular respiration. Which creates the bulk of the cells energy in the form of ATP
• 2 membranes
  * inner one has folds called cristae

-matrix is the cytoplasm

Question 19

Chloroplasts

Answer 19

-Perform photosynthesis

-2 boundary membranes + internal thylakoid membrane

• stroma is the “cytoplasm”

-stacks of thylakoids are called grana (singular=granum)

-photosynthetic reactions occur in thylakoids and stroma

Question 20

Other plastid types

Answer 20

Several others which defended from chloroplasts

Roles in storage and pigmentation

-chromoplast- holds pigment for organ coloration

• leucoplasts- no pigments
  * Amyloplast: starch storage
  * Proteinoplast: protein storage

Question 21

Cytoskeleton is what? And what types

Answer 21

Filamentous protein polymers

Types
* microtubules
* intermediate filaments
* microfilaments

Question 22

Cytoskeleton functions

Answer 22

• cell shape
• cell polarity
• cell division
• cell movement and migration
• intracellular transport and cytoplasmic organization

Question 23

Microtubules

Answer 23

• polymers made of tubulin
• made of 13 protofilaments
• have plus and minus ends which gives them an inherent polarity
• switch between growing (polymerization)/ and shortening (depolymerization)
• most growth/ shortening occurs at plus ends

Question 24

Microtubules functions

Answer 24

Cell shape and movement

Cell division

Provide tracks for intercellular organelle movement

Question 25

Microfilaments

Answer 25

Polymers of actin Two protofilaments form a helix Also have plus and minus ends, which give them an inherent polarity Also grow by polymerization and shorten by depolymerization Also most growth/ shortening at + ends

Question 26

Microfilaments functions

Answer 26

Cell shape and migration Cell division (mostly during cytokinesis) Organelle movement and cytoplasmic streaming in plants Components of contractile elements in muscle fibres

Question 27

Intermediate filaments

Answer 27

Polymers of intermediate filament proteins (many types) Varied composition depending on cell type Do not have polarity and dynamic like MTs/MFs Can be both inside and outside of the cell

Question 28

Intermediate filament functions

Answer 28

-structure/ support/ adhesion Examples: -extracellular matrix in mammals -collagen (structural component of skin and connective tissues) -keratin (hair nails and claws) - nuclear lamins (line inner surface of nuclear envelope In Animals)

Question 29

Why don’t plants and fungi have intermediate filaments

Answer 29

They have cell walls instead of

Question 30

Prokaryotic cytoskeleton

Answer 30

Have ancestral versions of both microtubules and microfilaments Similar functions to MTs and MFs *cell shape *cell division