Other Eukaryotic Cell Features

Question 1

Which organelles don’t have membranes?

Answer 1

• Ribosomes
• Cytoskeleton
• Centrioles

Question 2

How big are ribosomes?

Answer 2

About 20nm

Question 3

How are ribosomes structured?

Answer 3

• Small
• Spherical
• Made of ribosomal RNA

Question 4

Where and how are ribosomes made?

Answer 4

In nucleolus as two separate subunits, passing through nuclear envelope into cell cytoplasm and then combine

Question 5

Where do ribosomes end up in a cell?

Answer 5

• Some remain free in cytoplasm
• Some attach to endoplasmic reticulum

Question 6

What function do ribosomes bound to the RER exterior have?

Answer 6

Mainly synthesise proteins that will be exported outside cell

Question 7

What function do ribosomes have in the cytoplasm?

Answer 7

Singly or in clusters, primarily site of assembling proteins used in cell

Question 8

How are centrioles structured?

Answer 8

• Consist of two microtubule bundles at right angles
• Made of tubulin protein subunits, arranged to form a cylinder

Question 9

What is the function of centrioles in mitosis?

Answer 9

• Before dividing, spindle forms from centrioles
• Chromosomes attach to spindle middle and motor proteins walk along tubulin threads, pulling chromosomes to opposite cell ends

Question 10

What is the spindle in a centriole made from?

Answer 10

Threads of tubulin

Question 11

How are centrioles involved in forming cilia and undulipodia?

Answer 11

• Before cilia form, centropes multiply and line up beneath cell surface membrane
• Microtubules then sprout outwards from each centriole forming a cilium/undulipodium

Question 12

Where are centrioles usually absent from?

Answer 12

• Cells of higher plants
• May be in some unicellular green algae

Question 13

What is a cytoskeleton?

Answer 13

A network of protein structures within cytoplasm

Question 14

What does the cytoskeleton contain?

Answer 14

• Rod-like microfilaments made of protein actin subunits
• Intermediate filaments
• Straight, cylindrical microtubules
• Cytoskeleton motor proteins

Question 15

What is a microfilament?

Answer 15

Polymer of actin

Question 16

How big is each microfilament?

Answer 16

7nm in diameter

Question 17

How big are intermediate filaments?

Answer 17

10nm in diameter

Question 18

What are straight cylindrical microtubules made from?

Answer 18

Protein subunits called tubulin

Question 19

How big are straight cylindrical microtubules?

Answer 19

18-30nm

Question 20

What are 3 molecular motors?

Answer 20

• Myosins
• Kinesins
• Dyneins

Question 21

What are molecular motors?

Answer 21

• Enzymes
• Have site binding and allowing hydrolysis of ATP as energy source

Question 22

What do the protein microfilamnets in cytoplasm do?

Answer 22

• Give support
• Give mechanical strength
• Keep cell’s shape stable
• Allows cell movement

Question 23

What do microtubules provide for a cell?

Answer 23

• Shape and support
• Help substances and organelles to mive through cytoplasm

Question 24

How do microtubules allow organelles to move in the cytoplasm?

Answer 24

• Form track along which motor proteins walk and drag organelles from one cell part to another
• Form spindle before cell divides, enabling chromosomes to be moved

Question 25

What do microtubules make up?

Answer 25

• Cilia • Undulipodia • Centrioles

Question 26

What are intermediate filaments made from?

Answer 26

A variety of proteins

Question 27

What do intermediate filaments do?

Answer 27

• Anchor nucleus in cytoplasm • Extend between cells in some tissues between spherical junctions

Question 28

What happens when intermediate filaments extend between spherical junctions?

Answer 28

Enables cell-cell signalling, calling adherence to base membrane, stabilising tissues

Question 29

Where is a plant cell wall and what is it made from?

Answer 29

• Outside of plasma membrane • Made from bundles of cellulose fibres

Question 30

Why is the cell wall strong?

Answer 30

Prevents plant cells bursting when turgid

Question 31

What do the plant cell walls do?

Answer 31

• Provide strength and support • Maintain cell's shape • Contribute to strength and support of entire plant • Are permeable, allowing solutions to pass through

Question 32

What are fungi cell walls made from?

Answer 32

Chitin

Question 33

How many genes does the human genome have for kinesin?

Answer 33

45

Question 34

How is each kinesin gene different in the human genome and what does this allow?

Answer 34

• Different shaped tail domain • Can attach to different 'cargo' types to move it within cell