Chapter 4

What is a cell?

The smallest unit of life.

Who first used the term 'cell'?

Robert Hooke in the 1600s.

What are the three key principles of cell theory?

1. All living organisms are composed of one or more cells. 2. Cells are the basic unit of structure and function in organisms. 3. All cells arise from pre-existing cells.

What is the difference between prokaryotic and eukaryotic cells?

Only eukaryotic cells have a nucleus.

How long have prokaryotic cells existed?

Approximately 3.5 billion years.

How long have eukaryotic cells existed?

Approximately 2 billion years.

What are the two major groups of prokaryotes?

Bacteria and Archaea.

List four basic features of prokaryotic cells.

1. Plasma membrane 2. Cytoplasm 3. Ribosomes 4. DNA

What is the role of plasma membrane in prokaryotic cells?

It encloses the cell.

What organelles are present in eukaryotic cells?

Organelles such as nucleus, mitochondria, and chloroplasts.

How do plant cells differ from animal cells?

Plant cells have cell walls, chloroplasts, and central vacuoles, while animal cells have centrioles.

What is the endosymbiosis theory?

Mitochondria and chloroplasts evolved from engulfed bacteria.

What is evidence supporting the endosymbiosis theory?

Mitochondria and chloroplasts have their own DNA, double membranes, and can self-replicate.

What does the invagination theory explain?

Internal membranes formed by infolding of the plasma membrane.

What is the structure of the plasma membrane?

Phospholipid bilayer with hydrophilic heads and hydrophobic tails.

What are membrane proteins?

Proteins that perform various functions, such as receptor and transport proteins.

What is the fluid mosaic model?

The membrane is flexible and dynamic.

What disorder is related to faulty membranes?

Cystic Fibrosis.

What is the function of tight junctions?

To prevent leakage between cells.

What type of junction allows cell communication?

Gap junctions.

Describe passive transport.

Movement of molecules across a membrane without energy use.

What is osmosis?

Water movement across a membrane.

What occurs in a hypertonic solution?

Water exits the cell, causing it to shrink.

What is primary active transport?

Direct use of ATP to move molecules against their concentration gradient.

Define endocytosis.

Movement of large particles into the cell.

What is the function of the nucleus?

Control center of the cell, containing chromatin.

What is the function of mitochondria?

Converts food into ATP for energy.

What components make up the cytoskeleton?

Microtubules, intermediate filaments, and microfilaments.

What is the role of cilia?

To move fluids across the cell surface.

What is the significance of cell adaptation?

Cells adjust their composition based on environmental changes.

What is the fundamental unit of life?

The cell.

How do transport mechanisms contribute to cells?

They ensure balance and homeostasis.