Eukaryotic Animal Cells

Question 1

Nucleus

Answer 1

• contains codes genetic information in the form of DNA
• biggest organelle in the cell
• double membrane (nuclear envelope)
• nuclear envelope contains nuclear pores

Question 2

How does DNA leave the nucleus to get to protein synthesis in the cytoplasm?

Answer 2

It is transcribed into smaller RNA molecules which are exported via the nuclear pores.

Question 3

How are chromosomes formed?

Answer 3

DNA associated with proteins called histones to form a complex called chromatin which coils + condenses to form chromosomes. These only become visible when cells are preparing to divide.

Question 4

Nucleolus

Answer 4

• area within the nucleus
• responsible for producing ribosomes
• composed of proteins + RNA

Question 5

How are ribosomes used for protein synthesis made?

Answer 5

RNA is used to produce rRNA which is then combined with proteins to form the ribosomes necessary for protein synthesis m.

Question 6

Mitochondria

Answer 6

• site of final stages of cellular respiration
• the no. mitochondria reflects amount of energy cell uses
• double membrane (inner -> cristae
• fluid -> matrix
• membrane forming cristae contains enzymes used in aerobic respiration
• they can produce their own enzymes + reproduce themselves
• also contains its own (mt) DNA

Question 7

Vesicles

Answer 7

• membranous sacs
• storage + transport roles
• single membrane with fluid inside
• used to transport materials inside cell

Question 8

Lysosomes

Answer 8

• specialised forms of vesicles
• contain hydrolytic enzymes
• responsible for breaking down waste materials inside the cell ( old organelles )

Question 9

What important role do lysosomes play in the immune system?

Answer 9

They are responsible for breaking down pathogens ingested by phagocytic cells.

Question 10

Cytoskeleton

Answer 10

• network of fibres necessary for the shape + stability of a cell
• organelles are held in place by CS
• controls movement of cell and organelles

Question 11

Three components to the cytoskeleton

Answer 11

1. Microfiliments
2. Microtubules
3. Intermediate fibres

Question 12

Microfiliments

Answer 12

• contractile fibres formed from the protein actin
• cell movement + cell contraction during cytokinesis

Question 13

Microtubules

Answer 13

• globular tubulin proteins polymerise to form tubes that are used to form scaffold - like structure which determines shape of cell.
• act as tracks for the movement of cell
• spindle fibres are composed of Microtubules

Question 14

Intermediate fibres

Answer 14

• give mechanical strength to cells + help maintain their integrity

Question 15

Flagella

Answer 15

• used primarily to enable cell motility
• in some cells they’re used as a sensory organelle detecting chemical changes in the cells environment

Question 16

Cilia

Answer 16

• can be stationary or Mobile
• each cilium contains 2 central microtubules surrounded by 9 pairs of Microtubules, like a wheel
• pairs of parallel Microtubules slide over each other causing the cilia to move in a beating motion.

Question 17

Difference between stationary cilia and mobile cilia

Answer 17

Stationary - present in many cells. Mainly in sensory organs e.g. nose

Mobile - beat in a rhythmic manner. Causing fluid or objects to move. e.g. trachea.

Question 18

Organelles of Protein Synthesis

Answer 18

Ribosomes, Golgi + endoplasmic reticulum all play a key part in protein synthesis

Question 19

ER in protein synthesis

Answer 19

• Network of membranes enclosing flattened sacs called cisternae.
• Connected to the outer membrane of the nucleus.

Question 20

What is smooth ER in charge of?

Answer 20

Synthesising and storing Lipids and carbohydrates.

Question 21

What is the Rough ER in charge of?

Answer 21

Synthesis + transport of proteins.

Question 22

Ribosomes

Answer 22

• Two parts (subunits) -> Smaller subunit 40S + 60S. larger unit. They come together in protein synthesis.
• Not surrounded by a membrane
• Constructed of RNA molecules
• Mitochondria, chloroplasts + prokaryotic cells contain ribosomes

Question 23

Golgi Apparatus

Answer 23

• Compact structure formed of cisternae.
• Does not contain ribosomes.
• Modifies proteins + packages them into vesicles.