Review of Cells Types of cells

Cells are the smallest unit of living things. We can formally state this fact as “Cells are the fundamental units of life” Cells are too small to be seen by the naked eye

Scientists use high power microscopes, such as the SEM (scanning electron microscope) and the TEM (transmission electron microscope) With these microscopes, scientist have been able to study the structures of cells.

SEM clearly shows a nucleus TEM shows clearly the endoplasmic reticulum

Two Primary Types of Cells The two primary types of cells are eukaryotic and prokaryotic. Eukaryotic (true nucleus) means these cells have a nucleus. Examples of eukaryotic cells are animal, plant, fungi, and protist. Prokaryotic cells include bacteria and archaeans. They do NOT have a nucleus.

Achaeans are organisms have no nucleus or membrane bound organelles. Achaeans are similar to bacteria, but are different in that they perform some processes that are the same as eukaryotes, but they have no nucleus.

Images of Eukaryotic Cells

Images of Prokaryotic Cells

Prokaryote Facts Prokaryote single-celled organisms were the earliest and most primitive forms of life on Earth. Prokaryotes can live in the most primitive, harsh environments

What cells exists in mass numbers? The answer to this question would be bacterial cells. Scientist estimate that 95% of the cells in the human body are bacterial cells. Most of these bacterial cells are found in the digestive tract!!! YUCK

Cells contain genetic material Cells contain DNA in the form of nucleic acids. DNA contains all the information to control the cell. In eukaryotes, the DNA is found in the nucleus. In prokaryotes, the DNA is found in the cytoplasm

Organelles Cells contain structures called organelles that carry out specific functions.

Reproduction Different types of cells carry out different methods of reproduction. Prokaryotes divide by cloning themselves by a process called binary fission.

Most eukaryote cells divide by mitosis. Sex cells (or gametes) in eukaryotes divide by meiosis.

From cells to tissues Groups of similar cells form tissues. Following are examples of tissues. Draw and label these tissue examples

Muscle tissues a.Skeletal muscle b.Smooth muscle c.Cardiac muscle

Nervous system tissue Epithelial tissue (skin or cheek cells)

Red blood cells

How long do cells live? All cells have varying life spans. Some cells only live for a few days. Others can live for up to 6 weeks as in the digestive tract cells that function as our immune system. Pancreatic cells can live up to a year!!

Cells commit suicide When cells become damaged or unable to perform mitosis, they will naturally self destruct by a process called apoptosis. This is a natural process which helps the body to maintain a natural state of development. If a cell cannot apoptosize, cancer may incur.