Cell types

Question 1

What is a prokaryotic cell?

Answer 1

A prokaryotic cell is a type of cell that is small, unicellular and contains no internal membranes.

Question 2

What are the components of a prokaryotic cell?

Answer 2

Components of a prokaryotic cell include:
* cell wall
* plasma membrane
* cytoplasm
* naked DNA in a loop
* 70S ribosomes

There are other structures found in some prokaryotes.

Question 3

What is the role of a prokaryotic cell wall?

Answer 3

The role of a cell wall in prokaryotes is to maintain cell shape and prevent the cell from bursting due to water intake by osmosis.

Question 4

Explain the prokaryotic cell wall.

Answer 4

The cell wall is a rigid, protective layer located outside the plasma membrane of certain cells, including prokaryotes, plants, fungi, and some protists. It provides structural support, protection, and shape to the cell.

Question 5

What is the plasma membrane of a prokyratic cell?

Answer 5

The plasma membrane is the thin, flexible boundary that surrounds a cell, separating its internal environment from the external surroundings. It is composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates.

Question 6

Outline the functions of the plasma membrane in prokyratic.

Answer 6

Transporting Nutrients and Waste
It facilitates the intake of essential nutrients, such as glucose, and expels waste products.

Maintaining Homeostasis
By regulating ion concentrations, it ensures the cell’s internal environment remains stable.

Energy Production
In prokaryotes, the plasma membrane is the site of ATP production during cellular respiration, as they lack organelles like mitochondria.

Question 7

What are the components of cytoplasm in prokyratic cells?

Answer 7

The cytoplasm is the jelly-like substance inside a cell, excluding the nucleus, where various cellular activities occur.

Within the cytoplasm, you’ll find:
* Enzymes that catalyze biochemical reactions.
* Ribosomes that synthesize proteins.
* The nucleoid region, where the DNA resides.

Question 8

Define the term “naked” in relation to prokaryotic DNA.

Answer 8

Naked DNA refers to DNA that is not enclosed within a nucleus or bound to histone proteins. It exists freely in the cytoplasm of prokaryotic cells, such as bacteria and archaea, and in some environments outside of cells.

Prokaryotic cells lack a defined nucleus.
Instead, their DNA resides in the nucleoid region, a less dense area within the cytoplasm visible under an electron microscope.

The DNA is organized as a single, circular molecule, often referred to as “naked DNA” because it is not wrapped around histone proteins, as in eukaryotic cells.

Question 9

Outline the functions of 70s ribosomes in prokyratic cells.

Answer 9

70S ribosomes are small ribosomes found in prokaryotic cells, as well as in the mitochondria and chloroplasts of eukaryotic cells. They are responsible for protein synthesis, translating messenger RNA (mRNA) into functional proteins.

Question 10

Explain how the components of a prokaryotic cell all work together as an integrated system.

Answer 10

The cell wall and plasma membrane form a protective barrier while facilitating controlled exchanges with the environment.

The cytoplasm serves as the site for metabolic reactions and houses the ribosomes and DNA.

The naked DNA provides instructions for protein synthesis and cellular functions.

The ribosomes translate genetic information into proteins that perform structural and enzymatic roles.

Question 11

How do prokaryotic ribosomes compare with eukaryotic ribosomes?

Answer 11

Prokaryotic ribosomes (70S) are smaller than eukaryotic ribosomes (80S).

Question 12

Define eukaryote.

Answer 12

A eukaryote is a type of cell that contains a nucleus and membrane-bound organelles, enabling it to carry out specialized and coordinated functions. These cells are found in plants, animals, fungi, and protists.

Question 13

What are the components of an eukaryotic cell?

*names only

Answer 13

• plasma membrane
• compartmentalised cytoplasm
• 80S ribosomes
• nucleus
• mitochondria
• endoplasmic reticulum
• Golgi apparatus
• vesicles, including lysosomes
• cytoskeleton

Question 14

Outline the function of the nucleus in the eukaryotic cell.

Answer 14

It houses linear chromosomes composed of DNA and histone proteins.
The nuclear envelope contains pores for selective transport of RNA and proteins.
It also directs cellular activities by regulating gene expression, ensuring the accurate transmission of genetic information during cell division.

Question 15

Outline the function of the plasma membrane in the eukaryotic cell.

Answer 15

The plasma membrane regulates the exchange of substances, allowing nutrients in and waste out.
* Maintains homeostasis by controlling the internal environment.

It acts as the first line of defense and communication between the cell and its surroundings.

Question 16

Explain how parts of an eukratic cell work togather.

Answer 16

The plasma membrane regulates exchanges with the environment.
The cytoplasm hosts biochemical reactions, with organelles performing specialized tasks.
The nucleus directs activities, while mitochondria supply energy.
Vesicles, the ER, and the Golgi apparatus manage production, packaging, and transport.

Question 17

Define the term compartmentalisation in the context of cells.

Answer 17

Compartmentalisation refers to the separation of the cell interior into compartments, e.g. the mitochondrial matrix is separated from the rest of the cytoplasm.

Question 18

Describe the composition of eukaryotic chromosomes.

Answer 18

Eukaryotic chromosomes are made of DNA bound to histone proteins.

Question 19

What is the function of the Golgi apparatus?

Answer 19

The function of the Golgi apparatus is to modify molecules, e.g. proteins, before packaging them into vesicles for transport to their destination.

Question 20

What is the function of the endoplasmic reticulum?

Answer 20

The function of the endoplasmic reticulum is as follows:
rough endoplasmic reticulum:
* protein synthesis
* protein transport

smooth endoplasmic reticulum:
* lipid synthesis
* production of sex hormones
* calcium ion storage in muscle cells

Question 21

What are lysosomes?

Answer 21

Lysosomes are a type of vesicle containing hydrolytic enzymes. They are involved with breaking down:
* old organelles
* pathogens during phagocytosis
* biological molecules stored inside cellular vacuoles

Question 22

What are microtubules?

Answer 22

Microtubules are hollow fibres made of tubulin protein that form part of the cell’s cytoskeleton, providing support and enabling movement of substances around the cell.

Question 23

Compare the structure of DNA in prokaryotes and eukaryotes.

Answer 23

In prokaryotes:
* DNA is naked
* DNA is circular
* Has no introns

In eukaryotes:
* Has histones
* DNA is linear
* Has introns

Question 24

Compare the organelles in prokaryotes and eukaryotes.

Answer 24

In prokaryotes:
* No nucleus
* Has no compartments
* 70S ribosomes

In eukaryotes:
* Has nucleus
* Has compartments
* 80S ribosomes

Question 25

Compare the reproduction of prokaryotes and eukaryotes.

Answer 25

**Prokaryotes:** * Asexual only (binary fission) * Cells are haploid **Eukaryotes:** * Asexual or sexual * Haploid or diploid

Question 26

Compare the average size of prokaryotes and eukaryotes.

Answer 26

**Prokaryotes:** * Smaller (>10µm) * Unicellular organisms **Eukaryotes:** * Larger (~100µm) * Often multicellular

Question 27

State the reasons for structural variations among eukratic cells.

Answer 27

**Plants:** As autotrophs, they depend on chloroplasts for energy and cell walls for structural support. **Fungi:** As decomposers, they rely on chitin cell walls and smaller vacuoles for nutrient storage. **Animals:** As mobile heterotrophs, their flexible plasma membrane and centrioles enable movement and efficient cell division.

Question 28

How do the cell walls of plant cells and fungal cells differ?

Answer 28

The cell walls of plant and fungal cells differ in that plant cell walls are made of cellulose while fungal cell walls are made of chitin.

Question 29

How does vacuole size and function vary between different eukaryotic cell types?

Answer 29

In plant cells: large, permanent vacuoles used for carbohydrate storage and cell support In animal and fungal cells: small vacuoles with multiple functions, e.g. disposal of waste

Question 30

What are aseptate hyphae?

Answer 30

Aseptate hyphae are strands of fungal cells with no cross-walls to separate the cells. This means that the hyphae contain continuous cytoplasm and multiple nuclei.

Question 31

How are skeletal muscle cells atypical? | Exceptions to the cell theory

Answer 31

Skeletal muscle fibers are long and packed with multiple nuclei, a setup called a syncytium. Muscle fibers form when smaller cells (called myoblasts) merge together, keeping their nuclei in the process. Each nucleus controls part of the muscle fiber, ensuring it can grow, repair damage, and produce enough proteins for movement and strength.

Question 32

How are red blood cells atypical? | Exceptions to the cell theory

Answer 32

Mature red blood cells (RBCs) in mammals are unique because they don’t have a nucleus. This unusual design makes them highly efficient at carrying oxygen.

Question 33

How are phloem sieve tube elements atypical? | Exceptions to the cell theory

Answer 33

In plants, sieve tube elements are specialized cells that transport sugars through the phloem. They lack a nucleus and other organelles, but they don’t work alone—they have companion cells to help them.

Question 34

How do the unusual cell designs show how life evolves to solve specific challenges?

Answer 34

Fungi grow efficiently with flowing cytoplasm. Muscle cells handle high demands with many nuclei. Red blood cells maximize oxygen transport by losing their nucleus. Plant cells transport sugars efficiently with the help of companion cells.