What is a cell?

A cell is the smallest unit of life.

The cell theory states:

● All living things are made up of cells

● Cells are the basic units of structure and function in living things

● New cells are produced from existing cells

CELL THEORY 1. The basic unit of life is the cell. (Hooke)

• In 1665, an English scientist named Robert Hooke made an improved microscope and viewed thin slices of cork viewing plant cell walls

• Hooke named what he saw "cells"

CELL THEORY 2. All living things are made of 1 or more cells.

• Matthias Schleiden (botanist studying plants)

• Theodore Schwann (zoologist studying animals) stated that all living things were made of cells

Schleiden

Schwann

CELL THEORY 3. All cells divide & come from old cells. (Virchow)

Virchow

The different shapes of cells reflect their different functions.

• The long extensions that reach out in various directions from the nerve cell allows the cell to send and receive nerve impulses(messages)

• The flat, plate-like shape of skin cells suits their function of covering and protecting the surface of the body.

What limits cell size?

• Small cells can exchange substances(oxygen, nutrients, and carbon dioxide) more readily than larger cells because small objects have a higher surface area to volume ratio.

• So, the cells divide!

There are 2 kinds of cells:

• Eukaryotes – Have a nucleus

• Examples of eukaryotes are plants, animals, fungus, and protists

• More complicated

• Prokaryotes – Do NOT have a nucleus

• Examples of prokaryotes are bacteria

• Smaller than eukaryotes

• Less complicated

Prokaryotic Cells• No ______________

• No _________________________

• Examples: Bacteria

• Prokaryotic cells include the following features:– Smaller in size– DNA in a nucleoid region– Cell membrane– Ribosomes– Cell wall of peptidoglycan

Eukaryotic Cells

• Have _____________________

• Have _______________

• Larger than Prokaryotic Cells

• Examples:– animal cells, – plant cells,– fungi cells and– protist cells

Cells have specialized structures to carry out functions. These are called

organelles.

Cell Organelles:

• Nucleus – command center of the cell. Contains the cell’s genetic material in the form of DNA. ONLY FOUND IN EUKARYOTES

• Cytoplasm – the “gel” material inside the cell membrane but not in the nucleus. The organelles live inside the cytoplasm.

Cell Organelles:

• Endoplasmic Recticulum (ER) – makes lipids, proteins and other materials that are exported (taken out) of the cell.

• Rough ER – part of the ER that makes proteins. -Called “rough” because ribosomes are attached to the surface and makes it

look bumpy.• Smooth ER – part of the ER that makes lipids and contains enzymes. Also plays a

role in the detoxification of drugs. Ex.) Liver cells play a key role in detoxifying drugs, so they contain large amounts of Smooth ER.

-Called “smooth” because ribosomes are not attached to the surface.

Cell Organelles:

• Ribosomes – small particles of RNA and protein found throughout the cytoplasm. They produce proteins by following instructions that come from the nucleus.

Cell Organelles:

• Golgi Apparatus– modifies, sorts and packages the proteins that come from the Rough ER and either stores them or ships them out of the cell.

• Lysosome – removes waste from the cell.

Cell Organelles

• Vacuoles –saclike structures used to store materials such as water, salts, proteins, and carbohydrates.

Cell Organelles

• Mitochondria – converts food into energy that the cell can use. They are the power centers of the cell.

• Cytoskeleton – supports the cell and helps to maintain the shape.

Cell Organelles

• Cell membrane – regulates what enters and leaves the cell and also provides protection and support.

• Centriole-located near the nucleus and helps organize cell division. Not found in plant cells.

Cell Organelles• Nuclear membrane-

surrounds the nucleus and allows material to move in and out of the nucleus.

• Nucleolus- within the nucleus, where the assembly (making) of ribosomes begin.

Cell Organelles:

• Chloroplasts – ONLY FOUND IN PLANT CELLS

- captures energy from sunlight and converts it into chemical energy in plant cells.

• Cell Wall – ONLY FOUND IN PLANT CELLS

- provides support and protection for the plant cell.

• Peroxisomes—absorb nutrients, digest fatty acids, and alcohol

-breakdown toxic hydrogen peroxide to water