Cell Ultrastructure- Eukaryote Cell Structure

Question 1

Why do we say that the nucleus is the control centre of the cell?

Answer 1

It contains DNA organised into chromosomes that code for the synthesis of proteins in the cytoplasm.

Question 2

Why are chromosomes contained within the nucleus?

Answer 2

In the nucleus, the DNA is isolated from the reactions of the cytoplasm and is protected from damage.

Question 3

What are histones?

Answer 3

Histones are special proteins that support and protect DNA in a chromosome.

Question 4

What is chromatin?

Answer 4

The form chromosomes take when a cell is not dividing, where the chromosomes aren’t visible and the DNA is more diffusely organised.

Question 5

What is heterochromatin?

Answer 5

Heterochromatin is more densely packed chromatin which appears darker.

Question 6

What is euchromatin?

Answer 6

Euchromatin is less densely packed chromatin which appears lighter.

Question 7

What is the nucleolus?

Answer 7

A discrete structure in the nucleus which makes rRNA (ribosomal RNA) and uses it to make ribosomes.

Question 8

Describe the nuclear membrane/envelope.

Answer 8

The nuclear envelope is a double membrane with pores in it and has ribosomes attached (encrusted) to its outer surface.

Question 9

What is ER?

Answer 9

Endoplasmic Reticulum (ER)

Includes Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER)

Question 10

What is the role of SER?

Answer 10

Synthesis of lipids, detoxification of drugs and poisons, carbohydrate metabolism

SER does not have ribosomes attached

Question 11

What is the role of RER?

Answer 11

Scaffolding for ribosomes to synthesize proteins and distribute them through the ER

Primary protein structure is synthesized at the ribosome on the RER

Question 12

What is a ribosome?

Answer 12

Site of protein synthesis

Found attached to ER or free in the cytoplasm as polyribosomes

Question 13

How are ribosomes different in prokaryotic cells?

Answer 13

Prokaryotic cells have smaller ribosomes than eukaryotic cells

Question 14

What is the Golgi apparatus?

Answer 14

A series of curved flattened sacs called cisternae that modify, process, and package proteins

Question 15

Fill in the blank: Rough Endoplasmic Reticulum (RER) has _______ attached.

Answer 15

ribosomes

Question 16

Fill in the blank: Smooth Endoplasmic Reticulum (SER) does not have _______ attached.

Answer 16

ribosomes

Question 17

True or False: The primary protein structure is synthesized in the cisternae of the RER.

Answer 17

False

Question 18

List the roles of SER.

Answer 18

• Synthesis of lipids
• Detoxification of drugs and poisons
• Carbohydrate metabolism

Question 19

What structure extends throughout the cytoplasm and is involved in protein synthesis?

Answer 19

Endoplasmic Reticulum

Question 20

Why is the Golgi body described as being continually formed and broken down?

Answer 20

The Golgi body is continually formed and broken down due to its dynamic role in modifying, processing, and packaging proteins.

Question 21

Specifically, what does the Golgi do?

Answer 21

The Golgi modifies, processes, and packages proteins.

Question 22

Where do the vesicles go after being pinched off the maturing face of the Golgi?

Answer 22

The vesicles are transported within the cell or fuse with the cell surface membrane to release their protein outside (exocytosis).

Question 23

What is a lysosome?

Answer 23

A tiny vesicle containing hydrolytic enzymes, found in animal and fungal cells.

Question 24

What is the role of lysosomes?

Answer 24

Lysosomes fuse with other vesicles containing food, pathogens, and old organelles to digest or destroy the contents.

Question 25

Fill in the blank: The Golgi modifies, processes, and packages proteins by adding _______ to form glycoproteins.

Answer 25

carbohydrates

Question 26

Fill in the blank: The Golgi modifies, processes, and packages proteins by adding _______ to form lipoproteins.

Answer 26

lipids

Question 27

Fill in the blank: The Golgi modifies, processes, and packages proteins by adding _______ groups or cofactors.

Answer 27

prosthetic

Question 28

Fill in the blank: The Golgi modifies, processes, and packages proteins by joining _______ together to form quaternary structure.

Answer 28

polypeptides

Question 29

What processes are involved in the Golgi's function?

Answer 29

The processes include: * Adding carbohydrates to form glycoproteins * Adding lipids to form lipoproteins * Adding prosthetic groups or cofactors * Joining polypeptides together to form quaternary structure * Labelling, packaging, and sorting proteins for export * Forming lysosomes

Question 30

True or False: Lysosomes can break down the cell they are in.

Answer 30

True

Question 31

Answer 31

Question 32

What is the role of mitochondria?

Answer 32

Site of ATP synthesis during aerobic respiration ## Footnote Mitochondria contain cristae that hold respiratory enzymes and can be more numerous in cells with high energy demands.

Question 33

How does a cell with high energy demands meet its need for ATP?

Answer 33

By having more mitochondria and more deeply folded cristae ## Footnote These adaptations increase the surface area for ATP production.

Question 34

What structures are made from the hollow fibers we call microtubules?

Answer 34

Cytoskeleton, spindle fibres, centrioles, cilia, and flagella ## Footnote Microtubules play a crucial role in maintaining cell structure and facilitating movement.

Question 35

What is the cytoskeleton?

Answer 35

A network of fibres that maintains cell shape, anchors organelles, and aids movement of structures within the cell ## Footnote It is essential for the structural integrity of the cell.

Question 36

What is the role of spindle fibres?

Answer 36

Pull chromosomes apart during cell division (mitosis and meiosis) ## Footnote This process is critical for equal distribution of genetic material to daughter cells.

Question 37

What are centrioles?

Answer 37

Structures unique to animal cells that help assemble spindle fibres during cell division ## Footnote They are essential for the organization of the mitotic spindle.

Question 38

Distinguish between the terms cytoplasm, cytosol, and protoplasm.

Answer 38

Protoplasm: all cell contents including the nucleus and organelles; Cytoplasm: all cell contents excluding the nucleus; Cytosol: all contents excluding the nucleus and other membrane-bound organelles ## Footnote Understanding these terms is important for studying cell biology.

Question 39

What surrounds a cell and what is its role?

Answer 39

The cell surface membrane, which is selectively permeable and determines which substances can enter or leave a cell ## Footnote This membrane is crucial for maintaining homeostasis within the cell.