Cell Study Guide
 Unicellular organisms means that they have 1 cell
 Multicellular organisms have more than one cell
 We have 75 to 100 trillion cells in our bodies
 Cells are constantly changing; they grow and divide
 Humans have many different types of cells and they all have different jobs
 Skin cells can prevent germs from getting in your body
 Cells group together to make tissue
 Tissues group together to make organs
 Organs group together to make organ systems
 Cells are the building blocks of ALL life
 Everything living is made up of at least 1 cell
 Cells are the smallest organisms living
 There are cells specific to each body system, and their appearance relates
to the function of the cell
 Cells are alive and they need energy (sun, plants, animals) to live
 Every multicellular organism started off as one cell
 All cells have 5 basic functions:
o Use energy
o Reproduce
o Respond to their environment
o Grow and divide
o Get rid of waste
 Each cell has a specific job
 Some examples of unicellular organisms:
o Amoeba – looks like a big blob; eats by surrounding a food particle and
then brings food into the cell; moves by changing its
shape
o Bacteria – can be good and bad; must take in food
o Paramecium – has many “hairlike” structures that help
it move; uses these structures to help take in food; can see it without a
microscope but looks like a tiny speck.
o Algae – uses sunlight to make food
o Euglena – uses its whiplike part (tail “ish” shape) that moves it forward;
uses sunlight to make food
 Cells grow and divide and the new cells created are a copy of its parent…
 Cells ---- Tissue --- Organs --- Organ Systems
 Examples of multi-cellular organisms:
o Humans, Rabbit, Dog, Tree, Plants, Grasshopper, Cheetah, etc….
 Single Cell – One cell organisms in which all life processes are performed in
this one celled.
 Multi-cellular – Organisms that are made up of more than one cell and have
different cells that perform specialized functions in the organism.
 Organism – An individual form of life that may be one celled or multicellular;
plants, animals, bacteria, fungi and protests are all organisms. They are
capable of growing, reproducing and breaking down nutrients needed to live.
 All cells have a nucleus (brain of a cell), mitochondrion( cell energy
processing center – takes energy out of food), vacuole (storage space), cell
membrane (holds the cell together)
 Only plant cells have a Cell Wall (rigid structure surrounding the cell) and
Chloroplasts (contain chlorophyll that makes the plants green and allows the
plants to use the sun as energy.. photosynthesis)