Chapter 2 – Part 2 Cell Theory Cell Types

The Cell Theory 1. All living things are made of one or more cells 2. Cells are the basic units of structure and function in all organisms 3. All cells arise from preexisting cells

Cell Size There are many types of cells in our body, each with a different shape and function Some cells, like human egg cells, can be seen with the naked eye Other cells are very small, like sperm cells, and need a microscope to be seen

Cell Size

Humans have trillions of cells in the body Size of cells range from 5µm to 20µm in size ent/begin/cells/scale/

Cell Size Continued… Small cells function more efficiently than large cells If surface area to volume ratio is too low, substances cannot enter and leave the cell well enough to meet the cell’s needs Small cells have high surface area to volume ratio

Surface Area-to-Volume

Types of Cells Prokaryote – “Before nuclei” Eukaryote – “True nuclei”

Prokaryotes Consists of unicellular organisms Ex: Bacteria and archea Can live in many environments Ex: extreme temperatures, pH, and radiation

Prokaryotes Some can make their own food Grow and divide rapidly using asexual reproduction

Prokaryote Cells -Lacks a nucleus and most organelles -Much smaller than a eukaryote cell -One single circular strand of DNA found in the cytoplasm

Prokaryote Cells Continued… Plasmid: Circular strand of DNA Flagella: Aids in movement Pili : Helps bacteria attach to surfaces Capsule : a polysaccharide barrier used for protection

Eukaryotes Consists of unicellular and multicellular organisms Ex: Plants, animals, fungi, protists… Organisms can asexually and sexually reproduce

Eukaryote Cells Contains a nucleus with DNA and membrane-bound organelles Larger, more complex cells May have evolved from a prokaryotic cell

Types of Eukaryote Cells Plant Cells and Animal Cells