3.4 - Eukaryotic Cell Structure

Question 1

What is the nuclear envelope?

Answer 1

A double membrane that surrounds the nucleus

Question 2

What do nuclear pores do?

Answer 2

Allow the passage of large molecules, such as messenger mRNA, out of the nucleus

Question 3

What is the nucleoplasm?

Answer 3

Granular, jelly-like material that makes up the bulk of the nucleus

Question 4

What does the nucleolus do?

Answer 4

Manufactures ribosomal RNA and assembles the ribosomes

Question 5

What are the three functions of the nucleus?

Answer 5

• act as the control centre of the cell through the production of mRNA and tRNA and hence protein synthesis
• retain the genetic material of the cell in the form of DNA and chromosomes
• manufacture ribosomal RNA and ribosomes

Question 6

What is the role of the double membrane that surrounds the mitochondria

Answer 6

Controls the entry and exit of materials

Question 7

The inner of the two membranes of the mitochondria is folded to form extensions known as what?

Answer 7

Cristae

Question 8

What do crisaes provide?

Answer 8

A large surface area for the attachment of enzymes and other proteins involved in respiration

Question 9

What is the matrix?

Answer 9

Makes up the remainder of the mitochondria, it contains protein, lipids, ribosomes, and DNA that allows the mitochondria to control the production of some their own proteins

Question 10

What is the chloroplast envelope?

Answer 10

A double plasma membrane that surrounds the organelle, it is highly selective in what it allows to enter and leave

Question 11

What is the grana?

Answer 11

Stacks of up to 100 disc like structures called thylakoids

Question 12

What is within the thylakoids?

Answer 12

A photosynthetic pigment called chlorophyll

Question 13

What are the stroma?

Answer 13

A fluid filled matrix where the second stage of photosynthesis takes place

Question 14

What are the 3 ways that chloroplasts are adapted to their function?

Answer 14

• the granule membranes provide a large surface area for the attachment of chlorophyll, electron carriers and enzymes that carry out the first stage of photosynthesis
• the fluid of the stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis
• chloroplasts contains both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis

Question 15

What are the two types of endoplasmic reticulum?

Answer 15

• smooth
• rough

Question 16

What is the appearance of the rough ER

Answer 16

Has ribosomes present on the outer surface of the membrane

Question 17

What is the RERs function?

Answer 17

• provide a large surface area for the synthesis of proteins and glycoproteins
• provide a pathway for the transport of materials, especially proteins, throughout the cell

Question 18

What is the appearance of the SER look like?

Answer 18

It lacks ribosomes on its surface and is more tubular in appearance

Question 19

What is the function of the SER

Answer 19

• synthesise, store and transport lipids
• synthesis, store and transport carbohydrates

Question 20

What does the Golgi apparatus do?

Answer 20

• The proteins and lipids that are produced by the ER are passed though in strict sequence
• it modifies these proteins often adding non protein components such as carbohydrates to them
• it also labels them allowing them to be accurately sorted and sent to their correct destinations
• once sorted they are transported to the golgi vesicles
• the vesicles may move to the cell surface where they fuse with the membrane and release their contents to the outside

Question 21

What is the functions of the Golgi apparatus?

Answer 21

• add carbohydrate to proteins to form glycoproteins
• produce secretory enzymes, such as those secreted by the pancreas
• secrete carbohydrates, such as those used in making cell walls in plants
• transport, modify and store lipids
• form lysosomes

Question 22

When are lysosomes formed?

Answer 22

When the vesicles produced by the Golgi apparatus contain enzymes such as protease and lipases - also contain lysozymes

Question 23

What are the functions of a lysosome?

Answer 23

• hydrolyse material ingested by phagocytic cells, such as white blood cells and bacteria
• release enzymes to the outside of the cell (exocytosis) in order to destroy material around the cell
• digest worn out organelles so that the useful chemicals they are made of can be re used
• completely break down cells after they have died (autolysis)

Question 24

What are the two types of ribosomes?

Answer 24

• 80s
• 70s

Question 25

Where are 80s ribosomes found?

Answer 25

Found in eukaryotic cells

Question 26

Where are 70s ribosomes found?

Answer 26

Found in prokaryotic cells, mitochondria and chloroplasts

Question 27

What are the cell walls features?

Answer 27

- they consist of a number of polysaccharides such as cellulose - there is a thin layer called the middle lamella which marks the boundary between adjacent cell walls and cements adjacent cells together

Question 28

What are the functions of the cellulose cell wall?

Answer 28

- to provide mechanical strength in order to prevent the cell bursting under the pressure created by the osmotic entry of water - to give mechanical strength to the plant as a whole - to allow water to pass along it and so contribute to the movement of water through the plant

Question 29

What are the cell walls of fungi made up of?

Answer 29

Chitin

Question 30

What is the single membrane around the vacuole called?

Answer 30

Tonoplast

Question 31

What is the plant vacuoles functions?

Answer 31

- they support herbaceous plants and herbaceous parts of woody plants by making cells turgid - the sugars and amino acids may ac as a temporary food store - the pigments may colour petals to attract pollinating insects