2.1.4 - Eukaryotic cells 2 Flashcards

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1
Q

define the endoplasmic reticulum

A

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)

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2
Q

what are ribosomes made of?

A

ribosomal RNA and protein

- has a large and small subunit

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3
Q

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

A

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

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4
Q

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

A

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

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5
Q

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

A
  • mitochondria of eukaryotic cells

- chloroplast of plant cells

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6
Q

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

A
  • 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
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7
Q

define 80s ribosomes

A

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

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8
Q

define 70s ribosomes

A

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

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9
Q

define rough endoplasmic reticulum (RER)

A

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

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10
Q

define exocytosis

A

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.

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11
Q

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

A
  • 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
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12
Q

What allows the RER to synthesise many proteins?

A
  • a large surface area
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13
Q

what is special about the RER in the gut?

A
  • 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
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14
Q

define smooth endoplasmic reticulum

A

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

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15
Q

where can you find lots of SER?

A
  • 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
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16
Q

define the golgi apparatus

A

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

17
Q

what are cisternae?

A

the stacks of parallel, flattened membrane in the golgi apparatus

18
Q

how are cisternae formed?

A

by the fusing of vesicles from RER

19
Q

How do the RER and the golgi apparatus work together?

A
  • 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
20
Q

define a lysosome

A

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

21
Q

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

A
  • the inner areas
  • nearer the RER
  • where most enzymes/ membrane proteins are converted into the finished product
22
Q

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

A
  • the outer regions
  • you will find the finished protein products
  • therefore not many of the enzymes that make them
23
Q

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

A
  • 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
24
Q

what does ‘lysis’ mean?

A
  • breaking down
25
Q

where are lysosomes found?

A

in the cytoplasm of most cells

26
Q

what do lysosomes look like?

A
  • dark spherical bodies
27
Q

what do lysosomes contain?

A
  • powerful mic of digestive enzymes
28
Q

what is the function of a lysosome?

A
  • to break down/ destroy organelles in the cells of your body that are worn out
29
Q

describe the process of a lysosome breaking down an organelle.

A
  • 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)
30
Q

define apoptosis

A

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