Session 2 - General Characteristics, Structure And Function Of A Cell

Question 1

What are membranous organelles?

Answer 1

Cell organelle that are surrounded with a plasma membrane are isolate from the cytosol.

Question 2

Give 5 examples of membranous organelles.

Answer 2

Rough endoplasmic reticulum
Smooth endoplasmic reticulum
Glogi apparatus
Endosomes
Mitochondria

Question 3

What are non-membranous organelles?

Answer 3

Cell organelles that have no plasma membrane and are in direct contact with the cytosol.

Question 4

What are the functions of the cell membrane?

Answer 4

1. Physical isolation
2. Regulates exchange with environment - ions and nutrients enter and waste and cellular products are released through diffusion, osmosis, active transport and phagocytosis.
3. Monitors the environment - the extracellular fluid composition and chemical signals
4. Structural support - anchors cells and tissues

Question 5

Explain the mosaic model of the cell membrane.

Answer 5

It is about 8,5 -10 nanometers in cross section and has a double layer of phospholipid molecules. The majority of the lipid molecules are cholesterol. The cell membrane also contains integral and peripheral proteins as well as carbohydrates.

Question 6

List the 6 membrane proteins are explain their functions.

Answer 6

1. Structural proteins - junctions with neighbouring cells
2. Linkers - anchor intracellular skeleton to extracellular matrix
3. Enzymes - catalyse reactions
4. Receptor proteins - bind and respond to ligands (ions and hormones)
5. Carrier proteins - transport specific solutes through the membrane
6. Channels - regulate water flow and solutes through the membrane

Question 7

What is endocytosis?

Answer 7

A type of vesicular transport that used ATP to transport objects into the cell.

Question 8

What is exocytosis?

Answer 8

A type of vesicular transport that uses ATP to transport objects out of the cell.

Question 9

What are the categories of cellular transport?

Answer 9

1. Diffusion
2. Carrier-mediated transport
3. Vesicular transport

Question 10

What happens during phagocytosis?

Answer 10

Pseudopodia engulf large objects in phagosomes and transport them into through the cell membrane.

Question 11

What is the function of endosomes?

Answer 11

They sort and recycle protein internalised by endocytosis.

Question 12

What is the function of the rough endoplasmic reticulum?

Answer 12

Protein synthesis

Question 13

What are the functions of the smooth endoplasmic reticulum?

Answer 13

1. Synthesises steroid hormones
2. Responsible for the oxidation, conjugation and methylating process to neutralise certain hormones and detoxify poisonous substances.
3. Involved in metabolism (breaking down) of glycogen
4. Synthesises triglyceride
5. Resynthesises absorbed fatty acids and glycerol to form neutral fats
6. Plays a role in muscle contraction by concentrating and releasing calcium 2+ ions.

Question 14

What are the functions of the glogi apparatus?

Answer 14

1. Involved in protein production as proteins undergo changes in the sacculae.
2. Produces secretory vesicles, enzymes or hormones
3. Adds carbohydrates to proteins - glycoproteins

Question 15

What are the functions of the lysosome?

Answer 15

1. Breaking down large molecules
2. Attack bacteria
3. Recycling basic components of broken down damaged organelles
4. Ejecting waste products by exocytosis
5. Autolysis/post-mortem degeneration of tissues
6. Defend the body against certain bacterial invaders

Question 16

What is the function of peroxisomes?

Answer 16

1. They contain oxidases which regulate H2O2 levels
2. They break down fatty acids and organic compounds
3. Possibly responsible for gluconeogenesis

Question 17

What are the functions of mitochondria?

Answer 17

They provide most of the energy required for the cell:

1. Houses the chains of enzymes responsible for what is termed cell respiration

Question 18

Give 4 examples of non-membranous organelles.

Answer 18

1. Microtubuli
2. Actin filaments
3. Intermediate filaments
4. Ribosomes

Question 19

What are the functions of microtubules?

Answer 19

attach to the centrosome
strengthen the cell and anchor organelles
change the shape of the cell
move vesicles within the cell
form spindle apparatus

Question 20

What is the function of cilia?

Answer 20

They move fluids across the cell surface

Question 21

What is the structure of cilia?

Answer 21

They are composed of 9 peripheral duplets of microtubuli and 2 central microtubuli

Question 22

Where are basal bodies located?

Answer 22

At the base of cilia

Question 23

What is the structure of basal bodies?

Answer 23

They are composed of 9 peripheral triplets pf microtubuli.

Question 24

What are the functions of actin filaments?

Answer 24

Provide additional mechanical strength and interact with proteins for consistency.

Pair with thick filaments of myosin for muscle movement

Question 25

What are the functions of intermediate filaments?

Answer 25

1. Strengthen the cell and maintain shape. 2. Stabilise organelles 3. Stabilise cell position

Question 26

What is the function of the nucleus?

Answer 26

It is the control centre of the cell

Question 27

What are the components of the nucleus?

Answer 27

1. Chromatin 2. Nucleolus 3. Nuclear envelope which contains nuclear pores 4. Nucleoplasm

Question 28

Describe the structure of a chromosome from DNA until chromosome.

Answer 28

The double helix DNA strand coils around nucleosomes. The strand of nucleosomes coils to form chromatin fiber. The chromatin fibers form loops with domains and are anchored in non-histone protein and these then form a chromosome.

Question 29

What are cytoplasmic inclusions?

Answer 29

Non-living intracellular substances that are not bound by any membrane and do not carry out any metabolic activity

Question 30

Which cell structures contain microtubules?

Answer 30

1. MTOC 2. Centrioles 3. Basal bodies 4. Cilia 5. Flagella 6. Mitotic spindle

Question 31

What is the function of ribosomes?

Answer 31

Synthesise proteins for maintenance of the cell

Question 32

What is autophagy?

Answer 32

Autophagy is a housekeeping process whereby obsolete organelles and large protein aggregates are degraded and recycled.

Question 33

What is heterophagy?

Answer 33

when a cell ingest/phagocytose a substance from outside of the cell, into the cell. This substance is then digested within the cell.

Question 34

In which types of cells would the rough endoplasmic reticulum be well developed?

Answer 34

The rER will be well developed in all cells that produce large amounts of protein for export. Hepatocytes (liver cells) – secrete various proteins including albumin,… Mamary gland secretory cells – secrete milk protein. Salivary gland secretory cells – secrete enzymes in saliva (proteins).