2.4 Eukaryotic cell structure

Question 1

What are the 2 basic types of cells?

What is the difference between these cells?

Answer 1

Prokaryotes and Eukaryotes

PK:

• Simple undivided internal structure of only a cytoplasm
• Single celled

EK:

• Make up multicellular organisms (animals, plants, fungi)
• Complex internal structure (membrane-bound nucleus, membrane-bound organelles)

Question 2

What does metabolism involve?

Answer 2

Synthesis (anabolism) and break down of molecules

*(reactions take place in cytoplasm)

Question 3

Describe the properties and function of membranes

Answer 3

• Selectively permeable
• Separate cytoplasm from external environment
• Control movement of substances in/out of cell
• Quite fragile

Question 4

Common features in all eukaryotic cells

*Refer to Figure 3 on p.g. 27

Answer 4

• Microtubule network
• Vesicles
• Nucleolous
• Nucleus
• Golgi apparatus
• Cytosol
• Ribosome
• Centriole
• Cell-surface membrane
• RER (rough endoplasmic reticulum)
• SER (smooth endoplasmic reticulum)
• Cytoskeleton
• Mitochondria
• Secretory vesicles

Question 5

1. What does the nucleus contain?

2. What is the function of this?

Answer 5

1. Contains genetic info in the form of DNA

2. DNA directs synthesis of proteins - controls metabolism as many proteins are enzymes

Question 6

What is the nucleus in?

Answer 6

A double membrane - nuclear envelope

Question 7

What is the function of the nuclear envelope?

Answer 7

To protect the nucleus from damage in the cytoplasm

Question 8

What does the nuclear envelope contain?

Answer 8

Nuclear pores

Question 9

What is the function of nuclear pores?

Answer 9

Allow substances to move in and out of the nucleus

Question 10

How does DNA leave the nucleus?

Answer 10

DNA too big to leave nucleus - transcribed into smaller RNA molecules; exported via nuclear pores

Question 11

How is chromatin formed?

Answer 11

When DNA associates with histones (proteins)

Question 12

How are chromosomes formed?

Answer 12

Chromatin coils + condenses

Question 13

What is the nucleolus?

What is its function?

Answer 13

• Area within nucleus
• Made up of proteins and RNA

-Produces ribosomes

Question 14

What is RNA in the nucleolus used for?

Answer 14

To produce ribosomal RNA (rRNA), which is then combined w/ proteins to form ribosomes

Question 15

Describe the structure of the mitochondria

Answer 15

• Double membrane
• Inner membrane highly folded to form cristae
• Fluid interior = matrix
• Contain DNA - mitochondrial DNA (mtDNA)

Question 16

What is the function of the mitochondria?

Answer 16

• Site of cellular respiration
• Stored energy made available by producing ATP
• Amount reflects how much energy the cell uses - active cells = lots
• Membrane forming cristae contains enzymes for aerobic respiration
• Can produce own enzymes + reproduce on its own

Question 17

What are vesicles? What are they used for?

Answer 17

• Membranous sacs w/ storage + transport roles
• Consist of single membrane w/ fluid inside
• Used to transport materials inside cells

Question 18

What are lysosomes?

Answer 18

Specialised vesicles that contain hydrolytic enzymes

Question 19

What is the function of lysosomes

Answer 19

• Break down waste in cells
• Break down pathogens ingested by phagocytes
• Involved in programmed cell death (apoptosis)

Question 20

What is the cytoskeleton? Where is it?

Answer 20

1. Network of fibres required for shape and stability of
   the cell
2. Present throughout cytoplasm of eukaryotes

Question 21

What is the function of the cytoskeleton?

Answer 21

• Hold organelles in place

- Controls cell movement

Question 22

What are the 3 components of the cytoskeleton?

Answer 22

Microfilaments
Microtubules
Intermediate fibres

Question 23

What are microfilaments?

Answer 23

Contractile fibres made from actin
Responsible for cell movement and cell contraction during cytokinesis
*(Cytokinesis - when cytoplasm of 1 cell divides to form 2 daughter cells)

Question 24

What are microtubules?

Answer 24

• Determine cell’s shape

- Help move organelles - Act as path for movement of organelles

Question 25

What are spindle fibres?

Answer 25

- Made up of microtubules | - Role in chromosome separation during cell division

Question 26

What is the function of intermediate fibres?

Answer 26

- Give mechanical strength to cells | - Help maintain cell's integrity

Question 27

What are centrioles?

Answer 27

- Components of cytoskeleton in eukaryotes (not flowering plants or fungi) - Composed of microtubules - 2 centrioles = centrosome - Centrosome - involved in organisation of spindle fibres during cell division

Question 28

What is the flagella and cilia? Compare them

Answer 28

Extensions protruding from some cells | -Flagella = longer but cilia = present in greater numbers

Question 29

What are flagella used for?

Answer 29

- Enable cell motility | - Sensory organelles detecting chemical changes in cell's env.

Question 30

What 2 types can cilia be? Elaborate on them

Answer 30

Stationary: - On surface of cells - Roles in sensory organs e.g. nose Mobile: - Beat in rhythmic manner, creating current = causes adjacent fluid to move E.G. In trachea; move mucus away from lungs to keep air passage clean In fallopian tubes to move egg cells from ovary to uterus *(Cilia are made up of microtubules)

Question 31

What is the endoplasmic reticulum?

Answer 31

A network of membranes enclosing flattened sacs called cisternae -Connected to outer membrane of nucleus

Question 32

What is the role of the smooth endoplasmic reticulum (SER)?

Answer 32

Synthesis + storage of lipids + carbs

Question 33

What is the role of the rough endoplasmic reticulum | (RER)?

Answer 33

- Has ribosomes bound to surface | - Synthesis + transport of proteins

Question 34

Where can ribosomes be found?

Answer 34

- Free-floating in cytoplasm | - Attached to RER

Question 35

What are ribosomes?

Answer 35

- No membrane - Constructed of RNA made in nucleolus - Site of protein synthesis

Question 36

What is the golgi apparatus?

Answer 36

- Similar structure to SER - Compact structure formed of cisternae - No ribosomes

Question 37

What is the function of the golgi apparatus?

Answer 37

- Modifying proteins + packing them into vesicles: Secretory vesicles - if protein needs to leave cell Lysosomes - if protein stays in cell

Question 38

Describe the 5 stages of protein production

Answer 38

1) Proteins synthesised on ribosomes bound to RER 2) Pass into cisternae + packaged into transport vesicles 3) Vesicles containing the synthesised proteins move to Golgi apparatus via cytoskeleton 4) Vesicles fuse with Golgi apparatus - proteins enter. Proteins are structurally modified before leaving Golgi apparatus 5) Secretory vesicles carry protein, vesicle moves to + fuses with plasma membrane to release contents via exocytosis. Some vesicles form lysosomes - these contain enzymes for use in cells