Cytoskeleton, Plant Cells, and Organelle Functions

A set of Q&A flashcards covering cytoskeleton structure, plant-specific organelles, protein processing pathways, and major organelle functions.

What is the cytoskeleton?

A network of protein tubes and fibres that provides internal shape, support, and organization to the cell.

Give two main functions of the cytoskeleton.

Maintaining the cell’s shape and enabling cell movement.

Name the two primary types of cytoskeletal fibres.

Microfilaments and microtubules.

How would you describe microfilaments?

Solid, thread-like protein structures that form extensive frameworks inside the cell.

List two roles of microfilaments.

They bear mechanical stress and support cell movement, including muscle contraction.

Why can microfilaments quickly aid cell movement?

They can rapidly assemble and disassemble.

How would you describe microtubules?

Hollow protein structures within the cytoskeleton.

State three functions of microtubules.

Maintaining cell shape, separating chromosomes during cell division, and forming cilia and flagella.

What are centrioles?

Two short cylinders located near the nuclear membrane at right angles to each other.

What is the role of centrioles during cell division?

They organize microtubules to form the framework that separates chromosomes.

Which organelles are never found in plant cells?

Lysosomes, centrioles, and flagella (except in sperm).

Which organelles are absent in animal cells?

Plastids (including chloroplasts), a central vacuole, and a cell wall.

What is the main function of the plant cell wall?

To provide support and protection.

Of what material is the plant cell wall primarily composed?

Cellulose, a tough carbohydrate fibre.

Define the central vacuole.

A very large fluid-filled vacuole found in mature plant cells.

How does the central vacuole strengthen a plant cell?

When filled with water it generates turgor pressure that pushes against the cell wall.

Besides support, what other role does the central vacuole serve?

It stores organic compounds.

What is the main function of the Golgi apparatus?

To modify, sort, and package proteins received from the endoplasmic reticulum.

After modification in the Golgi, what are two possible fates of proteins?

They are either stored inside the cell or secreted outside the cell.

Define vesicles.

Small spherical sacs surrounded by a single membrane.

Give three examples of vesicle types.

Transport vesicles, lysosomes, and peroxisomes.

Outline the basic pathway of a protein destined for secretion.

(1) Assembled by ribosomes on rough ER → (2) Transported in vesicles to Golgi → (3) Modified in Golgi → (4) Packaged in vesicles → (5) Vesicles fuse with the plasma membrane to release the protein outside.

What are plastids?

Membrane-bound plant organelles with their own DNA.

Name the three main types of plastids.

Chloroplasts, chromoplasts, and leucoplasts (amyloplasts).

What is the primary function of chloroplasts?

They are the site of photosynthesis, converting solar energy into chemical energy stored in glucose.

Which pigment is located in thylakoids and what is its role?

Chlorophyll; it absorbs sunlight for photosynthesis.

What is the stroma in a chloroplast?

The dense fluid that surrounds the thylakoids.

What is the function of chromoplasts?

They contain non-green pigments that give fruits and flowers their colours.

What do leucoplasts store?

Starch in plant cells.

Where do lysosomes originate and what do they contain?

They bud from the Golgi apparatus and contain strong digestive (hydrolytic) enzymes.

What is the main role of lysosomal enzymes?

Breaking down large biomolecules and recycling the cell’s own organic material.

Why are lysosomes surrounded by a thick membrane?

To prevent their enzymes from escaping and destroying the cell.

What are peroxisomes?

Enzyme-containing vesicles not produced by the Golgi that break down harmful substances.

Give two functions of peroxisomes.

They break down alcohols and fatty acids and convert toxic hydrogen peroxide into water and oxygen.

Define a vacuole in general terms.

A membrane-bound storage compartment inside a cell.

List four substances that a vacuole might store.

Water, salts, proteins, and carbohydrates.

Why is the mitochondrion called the “powerhouse” of the cell?

It generates usable energy (ATP) through cellular respiration.

What is cellular respiration?

The conversion of glucose (sugar) into a usable form of energy (ATP) for the cell.

What are cristae and why are they important?

The folds of the inner mitochondrial membrane that increase surface area for respiration.

What evidence suggests mitochondria are semi-autonomous organelles?

They possess their own DNA and can replicate independently of the cell nucleus.