Cell Structure 2.1

What is a cell?

The smallest structural and functional unit of life. Every living organism starts from a single cell.

Why are cells important?

Cells multiply and specialize to form tissues, organs, and body systems.

Do all human cells have the same structures?

All cells share basic components, but some cells have extra structures depending on their specific function.

What is the plasma membrane?

A thin, flexible barrier made of phospholipids and proteins that surrounds the entire cell.

What does “selectively permeable” mean?

It means the plasma membrane allows only certain substances to enter or leave the cell.

What is the function of the plasma membrane?

It protects the cell and controls what moves in and out of it.

What is cytoplasm?

A jelly-like fluid that fills the inside of the cell. It is mostly water mixed with nutrients, salts, and waste products.

What is the function of cytoplasm?

It supports organelles and provides a medium where chemical reactions can happen.

What is the nucleus?

A large, round structure near the center of the cell that contains DNA.

What is DNA?

The cell’s genetic material. It carries instructions for cell growth, reproduction, and function.

What is the function of the nucleus?

It acts as the control center of the cell.

Why is the nucleus called the control center?

Because it directs cell growth, reproduction, and function.

What is the nuclear membrane?

A double-layered membrane with tiny pores that surrounds the nucleus.

What is the function of the nuclear membrane?

It protects the nucleus and allows certain materials, like RNA, to pass through.

What is the nucleolus?

A dense, dark structure inside the nucleus. Most cells contain 1–4 nucleoli.

What does the nucleolus produce?

It produces ribosomes and RNA.

Why is the nucleolus important?

It helps with protein synthesis by producing ribosomes and RNA.

What are mitochondria?

Rod-shaped organelles filled with fluid and their own DNA.

What is the nickname for mitochondria?

The “powerhouses” of the cell.

What is the function of mitochondria?

They convert nutrients into energy called ATP.

What is ATP?

The energy molecule used by cells.

What are ribosomes?

Small granules made of RNA. They can be free in the cytoplasm or attached to rough ER.

What is the function of ribosomes?

They build proteins used by the cell or sent outside the cell.

Where can ribosomes be found?

Free in the cytoplasm or attached to the rough endoplasmic reticulum.

What is the endoplasmic reticulum?

A network of membranes connecting the nucleus to other parts of the cell.

What are the two types of ER?

Rough ER and smooth ER.

What does rough ER do?

Produces and transports proteins.

Why is rough ER called “rough”?

Because ribosomes are attached to it.

What does smooth ER do?

Produces lipids and helps detoxify substances.

Why is smooth ER called “smooth”?

Because it does not have ribosomes attached.

What is the Golgi apparatus?

Stacks of flattened sacs located near the nucleus.

What is the nickname/function of the Golgi apparatus?

It acts like a “packaging and shipping center.”

What does the Golgi apparatus do?

It modifies, sorts, and packages materials for transport inside or outside the cell.

What are lysosomes?

Small sacs containing digestive enzymes. They are formed by the Golgi apparatus.

What is the function of lysosomes?

They break down waste, damaged cell parts, and harmful substances.

What is the cytoskeleton?

A framework of protein filaments and tubules throughout the cytoplasm.

What does the cytoskeleton do?

It maintains cell shape, provides structure, and helps organelles move.

What are centrioles?

A pair of cylindrical structures made of microtubules, usually near the nucleus.

What is the function of centrioles?

They help organize cell division by distributing DNA evenly between new cells.

What are cilia?

Short, hair-like projections on the cell surface.

What is the function of cilia?

They move substances across the cell surface, such as in respiratory passages.

What are flagella?

Long, whip-like extensions from the cell membrane.

What is the function of flagella?

They propel the cell forward.

What is an example of a cell with a flagellum?

A sperm cell, which uses its tail to move forward.

Which organelle contains DNA and controls the cell?

Nucleus

Which organelle makes ATP?

Mitochondria

Which organelle makes proteins?

Ribosomes

Which organelle packages and ships materials?

Golgi apparatus.

Which organelle breaks down waste and damaged cell parts?

Lysosomes

Which structure controls what enters and leaves the cell?

Plasma membrane

Which cell part supports organelles and chemical reactions?

Cytoplasm

Which structure helps during cell division?

Centrioles

Which cell structures help with movement across or through fluid?

Cilia and flagella

What is the difference between cilia and flagella?

Cilia are short and move substances across the cell surface; flagella are long and move the entire cell.

What is the difference between rough ER and smooth ER?

Rough ER makes/transports proteins; smooth ER makes lipids and detoxifies substances.

What is the relationship between nucleolus, ribosomes, and protein synthesis?

The nucleolus produces ribosomes and RNA, and ribosomes build proteins.

What is the relationship between Golgi apparatus and lysosomes?

Lysosomes are formed by the Golgi apparatus.

Why do medical assistants need to understand cell structure?

It helps them understand how the body works at a microscopic level and how diseases disrupt normal cell function.

What bigger topics does cell structure prepare you for?

Tissues, organs, body systems, and disease processes.

What is the main idea of cell structure?

Cells are the basic building blocks of life, and each part has a specific job that keeps the cell alive and functioning.