2.1.4 - Eukaryotic cells 2

Question 1

define the endoplasmic reticulum

Answer 1

3D network of membrane-bound cavities in the cytoplasm that links the nuclear membrane and makes up a large part of the cellular transport system (and synthesis of many different chemicals)

Question 2

what are ribosomes made of?

Answer 2

ribosomal RNA and protein

- has a large and small subunit

Question 3

what are the main type of ribosomes found in eukaryotic cells?

Answer 3

80s ribosomes
- 60s as the large subunit
- 40s as the small subunit
ratio of RNA : protein = 1: 1

Question 4

What are the main type of ribosomes found in prokaryotic cells?

Answer 4

70s ribosomes
- 30s small subunit
- 50s large subunit
ratio of RNA : protein = 2:1

Question 5

Other than prokaryotic cells, where are 70s ribosomes found?

Answer 5

• mitochondria of eukaryotic cells

- chloroplast of plant cells

Question 6

Why do 70s ribosomes provide evidence for the endosymbiotic theory?

Answer 6

• 70s are reproduced independently in the mitochondria and chloroplast when a cell divides
• evidence that both of them evolved from bacteria
• caught inside eukaryotic cells very early in the process of evolution
• 70s ribosomes usually found in prokaryotic cells

Question 7

define 80s ribosomes

Answer 7

main type of ribosome found in eukaryotic cells consisting of ribosomal RNA and protein (60s and 40s subunit) and are the site of protein synthesis

Question 8

define 70s ribosomes

Answer 8

found in mitochondria and chloroplast of eukaryotic cells and in prokaryotic organisms

Question 9

define rough endoplasmic reticulum (RER)

Answer 9

endoplasmic reticulum that is covered in 80s ribosomes and is involved in the production and transport of proteins

Question 10

define exocytosis

Answer 10

the energy-requiring process by which a vesicle fuses with the cell surface membrane so the contents are released to the outside of the cell.

Question 11

What are the roles of RER and 80s ribosomes in the production of proteins?

Answer 11

• 80s ribosomes makes the proteins
• RER isolates and transports the proteins once they have been made
• exocytosis is used to secrete proteins outside the cell without it interfering with the cell’s activities

Question 12

What allows the RER to synthesise many proteins?

Answer 12

• a large surface area

Question 13

what is special about the RER in the gut?

Answer 13

• it has large surface area
• as it produces digestive enzymes
• these are needed within the gut so a large surface area means a lot can be made

Question 14

define smooth endoplasmic reticulum

Answer 14

smooth tubular structure similar to RER but without the ribosomes, it is involved in the synthesis and transport of steroids and lipids in the cell

Question 15

where can you find lots of SER?

Answer 15

• testes, makes the steroid hormone testosterone
• liver, it metabolises cholesterol amongst other lipids
• amount and type of ER will give an idea of the type of job the cell does

Question 16

define the golgi apparatus

Answer 16

stacks of membranes that modify proteins made elsewhere in the cell and package them into vesicles for transport (also produce materials for plant cell walls and insect cuticles) - lined with SER

Question 17

what are cisternae?

Answer 17

the stacks of parallel, flattened membrane in the golgi apparatus

Question 18

how are cisternae formed?

Answer 18

by the fusing of vesicles from RER

Question 19

How do the RER and the golgi apparatus work together?

Answer 19

• proteins brought to the golgi apparatus in vesicles that are pinched off from the RER where they are made
• vesicles fuse with membrane sacs of golgi apparatus and the protein enters the golgi stacks
• proteins travel through the golgi and are modified

Question 20

define a lysosome

Answer 20

an organelle full of digestive enzymes used to break down worn out cells/ organelles or digest food in simple organisms

Question 21

What part of the golgi apparatus is very rich in enzymes?

Answer 21

• the inner areas
• nearer the RER
• where most enzymes/ membrane proteins are converted into the finished product

Question 22

What part of the golgi apparatus is not very rich in enzymes?

Answer 22

• the outer regions
• you will find the finished protein products
• therefore not many of the enzymes that make them

Question 23

how do proteins get to the outside of the cell from the golgi apparatus?

Answer 23

• vesicles containing secretions pinched off the golgi apparatus
• these vesicles then fuse with the cell surface membrane and release the secretions to the outside of the cell

Question 24

what does ‘lysis’ mean?

Answer 24

• breaking down

Question 25

where are lysosomes found?

Answer 25

in the cytoplasm of most cells

Question 26

what do lysosomes look like?

Answer 26

• dark spherical bodies

Question 27

what do lysosomes contain?

Answer 27

• powerful mic of digestive enzymes

Question 28

what is the function of a lysosome?

Answer 28

• to break down/ destroy organelles in the cells of your body that are worn out

Question 29

describe the process of a lysosome breaking down an organelle.

Answer 29

• fuse with each other
• enzymes break down contents into molecules that can be reused
• lysosome can fuse with outer cell membrane to release its enzymes outside the cell as extracellular enzymes (e.g to destroy bacteria)

Question 30

define apoptosis

Answer 30

programmed cell death - the breakdown of worn out, damaged or diseased cells by the lysosomes
- they rupture to release their enzymes in the cell and destroy the contents