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Biology Unit 2: Cells by

The Cell Theory

1. All things are made of cells
2. Cells are the basic units of structure and function in all living things
3. All cells come from preexi­sting cells


- Water with some chemicals and minerals that surrounds organelles
- Where messages pass through

Cell Membra­ne/­Plasma Membrane

-Surrounds the cell
-Two identical layers (bilayers) made of lipids
-Proteins that act like doors are embedded in the membrane
-Carbo­hydrate patterns that are unique to every person are on the outside of the membrane; these allow their bodies to recognize which cells are their's and fight off the ones that are not


- Small organelle that makes proteins
- Made of two sub units, one big, one small, the big one is on the top
- Free Ribosomes: Ribosomes floating in the cytoplasm, the proteins they make are used inside the cell
- Bound Ribosomes Ribosomes attached to the endopl­asmic reticulm, the proteins they make are sent and used outside the cell
- Some cells have more ribosomes than other cells


- Found in plants, bacteria and protists
- Use light, carbon dioxide and water in photos­ynt­hesis to make glucose
- Also has cristae
- The cristae are in stacks called thylakoid membranes
* Thylakoid membranes look like stacked coins
- Holds pigments such as chloro­phyll


Contains enzymes to break down:
-Food (in food vacuoles)
-Old organelles
-Cellular debris


When molecules in a liquid or gas state move from a more concen­trated place to a less concen­trated place.

Facili­tated Diffusion

Sometimes, the membrane will not let a molecule through so the cell will use facili­tated diffusion which is when a protein helps move the molecule across the membrane. It also doesn't require energy.


Diffusion for water.

Five Kingdoms of Living Things

1. Plants
2. Animals
3. Fungi
4. Bacteria
5. Protists


- Powerhouse of the cell
- Produces ATP using glucose
- Two layers for more surface area, the inner layer is the cristae
- Different cells can have more or less mitoch­ondria than different cells
- Plants also have mitoch­ondria

Endopl­asmic Reticulum

- Highway where chemicals are transp­orted around the cell
- Endopl­asmic reticulum means interc­ellular network
- Smooth ER: Detoxifies things (breaks down bad chemicals)
- Rough ER: Has ribosomes, sends proteins to other places in the cell


- Sacs used for storing anything (ie: food, water, salts, pigment, gases)
- Vacuoles in plant cells are huge (they are used when the plant has no other nutrition) and hold all other pigments except green, which is in the chloro­plasts
- Vacuoles also provide support and store poison in poisonous plants

Vocab Words

Sponta­neous Generation
The (false) idea that living things can come from nonliving things
Autotr­ophic Cells
Cells that use sunlight to make food
Hetero­trophic Cells
Cells that cannot make their own food
Eukaryotic Cells
Cells that have a nucleus
Prokar­yotic Cells
Cells that don't have nuclei
The ability of an organism to keep it's internal enviro­nment suitable for living
A hormone made in the pancreas that controls blood sugar
Channel Protein
A protein that moves molecules across the cell membrane

Cell Wall

- In plants, fungi and protists but not animals
- Porous to let things through
- Rigid (100x thicker than membrane)
- Maintains shape and protects cells
- Attaches to other cell walls to form strong structures (plants need to be strong but don't have skeletons)


- Brain of cell
- Holds DNA (23 pairs of chromo­somes)
- Nuclear Membrane: Also porus
- Nucleolus: Densest part, makes ribosomes
*Bacteria have no nuclei so the DNA just floats around in the cytoplasm

Golgi Apparatus

- Puts molecules in vesicles and ships them around or out of cells
- Receives things from other cells
- Looks like flattened sacks that look like pita bread
- Has a receiving side (cis face) and a shipping side (trans face)
- Golgi apparatus "­fin­ish­es" packaging things after the rough ER


- Skeleton of cell (ie: microf­ila­ments, microt­ubes)
- Some cells can move using:
Flagella: few, long, whip-like structures outside the cells
Cillia: hundreds of short, hairlike structures outside the cells


- Skeleton of cell (ie: microf­ila­ments, microt­ubes)
- Some cells can move using:
Flagella: few, long, whip-like structures outside the cells
Cillia: hundreds of short, hairlike structures outside the cells


Permeable Membrane: A membrane that lets everything through.
Semipe­rmeable Membrane: A membrane that lets some things through.
Imperm­eable Membrane: A membrane that doesn't let things through.

Active Transport

Using energy and a protein to force a molecule through the membrane against the concen­tration gradient.

Important Scientists

Robert Hooke: 1665 Looked at a cork an saw little chambers that he named cells because they looked like rooms in a monastery.
Antony Van Leeuwe­nhock: 1665 Saw living cells and called them animal­cules.
Matthias Schleiden: 1839 Said plants were made of cells.
Theodor Schwann: 1839 Said animals were made of cells.
-Together, Schleiden and Schwann first proposed the Cell Theory.
Rudof Virchow: 1855 Said that cells always came from preexi­sting cells.


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