Cell Organelles

Question 1

What are the 2 components of the cytoplasm?

Answer 1

1. The cytosol (intracellular fluid)
2. The organelles

Question 2

What is Cytosol?

Answer 2

The site for ezyme controlled reactions. (conventional cytoplasm)

-55% of cell volume and is 70-90% water
- Contains dissolved ions, glucose, amino acids, ATP, lipids and waste products

Question 3

What is the cytoskeleton and its function?

Answer 3

Network of protein filament extending throughout cytomplasm

• Helps maintain shape and internal organisation
• Provides mechanical support - for devision and movemnet

Question 4

What are the 3 main types of cytoskeleton?

Answer 4

1. Microfilaments
2. Intermediate filaments
3. Microtubules

Question 5

What are microfilaments?

Answer 5

Filaments that surround the edge of the cell - help generate movement

ACTIN and MYOSIN

create microvilli eg in small intestine

Question 6

Give 3 examples of Intermdediate filaments and their function

Answer 6

Keratin, vimentin and lamin

• Strong structures in parts of cell subject to mechanical stress.
  They stabalise positions of organelles

Question 7

What are microtubules?

Answer 7

Long, unbranched hollow tubules made from tubulin that form in the centrosome, then radiate outwards

• Help with cell strength, shape and movement of organelles . Eg vesicles and division

Provide structure to flagella. e.g. spermatozoa

Question 8

What is the centromere and where is it found?

Answer 8

Main microtubule organising centre and regulator of cell cycle progression. Grows miotic spindle during cell division

Found near nucleus

Question 9

What does centromere consist of?

Answer 9

2 centrioles;

Cylindrical structures - 9 clusters of microtubule triplets, both at right angles to each other

Question 10

What surrounds the centrioles and what does it consist of?

Answer 10

Pericentriolar material

Consists of
numerous rings of tubulin

Question 11

When does number of centrosome change?

Answer 11

Non dividing cells - single centrosome
Begins to divide - centrosome replicates early in process

The spindle apparatus forms after centrosome replication

Question 12

What is cillia?

Answer 12

Numerous, short hair like projections.

These transport fluid along cell surfaces

Question 13

What do female smoker have increased risk of?

Answer 13

Ectopic pregnancy - due to destroyed cillia in uterus

Question 14

What are flagella?

Answer 14

Similar structures to cillia but longer and often found singularily

Eg. sperm tail

Question 15

What is the endoplasmic reticulum?

Answer 15

Network of membranes in the form of flattened sacs and tubules extending from the nuclear envelope into the cytoplasm

Question 16

What is Rough ER?

Answer 16

Structure where proteins made by ribrosomes enter for sorting and processing

Question 17

What are ribrosomes?

Answer 17

Sites of protein synthesis

-Rich in RNA and contain >50 proteins each

Can be found free in cytoplasm, in mitochondria or on ER

Question 18

What is the Smooth ER?

Answer 18

Extension of rough ER without ribrosomes.

• synthesise fatty acids and steriods (eg. estrogens and testosterone)
• Releace glucose in liver
• detoxify lipid soluble drugs eg. alcohol and pesticides
• store Ca2+ ions in muscles

Question 19

Give an example of a fdrug that changes rough ER in liver cells when used repeatedly

Answer 19

Phenobarbital - more needed to feel affect as more smooth ER

Question 20

What is the golgi complex?

Answer 20

3-20 membranous cisternae (sac like structures) with bulging edges arranged in a stack

Entry cis face faces ER
Exit trans face faces plasma membrane

Question 21

What is the function of lysosomes?

Answer 21

Digestion of substances entering the cell, worn out organelles (autophagy) and entire cells (autolysis)

Question 22

What is Tay - Sachs disease?

Answer 22

Inherited condition affecting children that casues seisures, muscle regidity and become blind.

Death is often before age 5

Question 23

What causes Tay - Sachs disease?

Answer 23

Mutation of lysomal enzyme Hex A

Hex A is meant to break down GM2, which is prevelant in nerve cells.

Absence of Hex A means GM2 builds up and destroys nerve cell function

Question 24

What are peroxisomes?

Answer 24

Simar structures to lysosomes but smaller

• Contain oxidases
• Metablosise amino acids and fatty acis
• Oxidise toxic substances such as alcohol - lots in liver
• Contain enzyme catalase to protect against toxic hydrogen peroxide (made in oxidation reactions)