Week 6 - Golgi and Membrane Systems

Question 1

Q: What is the most abundant polar lipid found in thylakoid membranes?

Answer 1

chlorophyll, which is essential for photosynthesis in plants.

Question 2

Q: What percentage of life in the world’s oceans is comprised of tiny prokaryotes?

Answer 2

Tiny prokaryotes comprise about 30% of life in the world’s oceans.

Question 3

What is the role of the Golgi apparatus in cells?

Answer 3

The Golgi apparatus processes, modifies, and packages proteins and polysaccharides for transport to their destinations.

Question 4

Describe the two models of protein movement through the Golgi apparatus:

Answer 4

1. the vesicle transport model, where transport vesicles individually move proteins
2. the cisternal maturation model where the Golgi cisternae mature and progress through the stack.

Question 5

What type of vesicles are involved in protein secretion and how are they formed?

Answer 5

A: Coated vesicles, formed by scaffolding proteins like clathrin, are involved in protein secretion and transport.

Question 5

What is exocytosis?

Answer 5

Exocytosis is the process by which vesicles fuse with the plasma membrane to release their contents outside the cell.

Question 6

Why do cells utilize endocytosis?

Answer 6

Cells use endocytosis to:

1. maintain cell surface area
2. uptake target molecules
3. retrieve plasma membrane and extracellular fluid

Question 7

How do lysosomes function in the degradation of materials?

Answer 7

Lysosomes are membrane-bound organelles containing hydrolytic enzymes that digest ingested components, such as bacteria, and recycle cellular material

Question 8

What is the extracellular matrix (ECM) and its significance in animal cells?

Answer 8

The ECM is a network of proteins and polysaccharides that supports cell communication, attachment, and regulates cell behavior.

Question 9

What are tight junctions and their function?

Answer 9

Tight junctions are connections between adjacent cells that prevent the movement of molecules through the intercellular space, helping control the passage of substances.

Question 10

How do plasmodesmata differ from gap junctions?

Answer 10

Plasmodesmata are continuous membrane-lined channels between plant cells, while gap junctions are protein-based channels in animal cells that allow communication between adjacent cells.

Question 11

What are the three main components of the cytoskeleton?

Answer 11

The three main components are microfilaments (actin), intermediate filaments, and microtubules (tubulin).

Question 12

Q: How do microtubules facilitate intracellular transport?

Answer 12

Microtubules provide tracks for motor proteins like kinesin and dynein to move organelles and other cargo within the cell

Question 13

Describe the role of actin in muscle contraction:

Answer 13

During muscle contraction, myosin heads bind to actin filaments, and ATP hydrolysis causes conformational changes in myosin, enabling it to “walk” along the actin filaments.

Question 14

What does the golgi apparatus do as the processing centre for proteins?

Answer 14

modification and packaging
Polysaccharides are also made in the golgi
The golgi has stacks of membranes that move, add or replace sugars

Question 15

What is the role of microfilaments?

Answer 15

composed of actin, support cell shape, enable intracellular movement, facilitate muscle contraction, and form structures like filopodia and microvilli to increase surface area for nutrient absorption.

Question 16

How do proteins move through golgi? (two models)

Answer 16

Transport vesicles (vesicle transport model)
Individually move by themselves (cisternal maturation model)

Question 17

Explain the role of clathrin in vesicle formation during endocytosis:

Answer 17

Clathrin proteins coat specific areas of the plasma membrane, inducing membrane invagination to form a vesicle. After the vesicle is formed, clathrin is removed, allowing the vesicle to fuse with target membranes.

Question 18

Q: What is the function of plasmodesmata in plant cells?

Answer 18

Plasmodesmata are channels between plant cell walls that allow for the direct exchange of ions and small molecules between adjacent cells, facilitating communication and transport of nutrients

Question 19

How do plant vacuoles differ from lysosomes in animal cells?

Answer 19

Plant vacuoles store nutrients and waste and help maintain turgor pressure, while lysosomes primarily digest cellular waste and foreign materials.

Question 20

Q: What are the roles of kinesins and dyneins in cellular transport?

Answer 20

A: Kinesins and dyneins are motor proteins that transport organelles along microtubules. Kinesins typically move towards the plus end of microtubules, while dyneins move towards the minus end, facilitating intracellular transport in opposite directions.

Question 21

What types of junctions facilitate communication between animal cells?

Answer 21

Tight junctions create barriers, while gap junctions allow for the direct exchange of ions and small molecules between adjacent cells

Question 21

Q: What role does the Casparian strip play in plant roots?

Answer 21

A: The Casparian strip acts as a selective barrier, regulating the movement of water and solutes into the plant’s vascular system.

Question 22

Q: What triggers exocytosis in a cell?

Answer 22

Exocytosis is typically triggered by an increase in intracellular calcium levels, which stimulates vesicle fusion with the plasma membrane

Question 23

Q: How do clathrin-coated vesicles form?

Answer 23

Clathrin proteins bind to the membrane and induce curvature, forming a bud that eventually pinches off to create a coated vesicle

Question 24

How are vacuoles more varied than lysosomes?

Answer 24

Plant vacuoles are also storage compartments and are multifunctional, unlike lysosomes
Encompass 30-90% of the cell volume and store nutrients, pigments and waste materials

Question 25

How is animal and plant cell wall similar?

Answer 25

Both have strong tensile fibres embedded in a hydrated gel-like matrix made with polysaccharides

Question 26

What is the main connective tissue in animals?

Answer 26

collagen main connective tissue, 25-35% of protein content, tendons, skins, cornea, cartilage, teeth - food industry, medical uses

Question 27

Which is stronger? Plant cell wall or ECM

Answer 27

Plant cell walls are stronger and more rigid than the animal ECM
Plant cell walls form box like compartments to encase and immobilise cells
The boxes of cell walls can be stretched perpendicular to cellulose microfibrils
Plant cell wall can change with turgor pressure

Question 28

How is plant structure built in steps?

Answer 28

Asymmetric division and progression divisions create files of cells
This is all controlled by microtubules, next to the plasma membrane control the movement of cellulose synthase enzymes and control the orientation of cellulose microfibrils
Cellulose is synthesised by rosette structure of enzymes