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Chapter 7
Biology 
Cells
 What you will learn…
 1. What is a cell?
 2. Cell Theory
 3. Cells Size
 4. Two main cell categories: Prokaryotes and Eukaryotes
 5. Prokaryote cell structures
 6. Eukaryote cell structures: Plant and Animal
What is a cell?
 Cells are the basic units of life.
What is the Cell Theory?
 Collectively, the research of Schleiden, Schwann, and
Virchow led to the formation of the Cell Theory:
 1. All living things are made up of cells.
 2. Cells are the basic units of structure and function in
living things.
 3. New cells are produced from existing cells.
Every cell must have…
 DNA
 Cytoplasm
 Cell Membrane
 Ribosomes
Cells are small!
 Cells are microscopic; they are visible only with light
microscopes.
 Most of their size ranges from 1-100 µm.
 They have to be able to carry materials from one side of the
cell to the next in a short period of time.
 They must have a large enough surface area to be able to
take in nutrients and oxygen and release waste quickly.
The surface-to-volume ratio must
be large!
Two main categories of cells:
 Prokaryote:
 Cells that do not enclose their DNA in nuclei
 Eukaryote
 Cells that do enclose their DNA in nuclei
Prokaryotes
 small cells (about 1-10 µm) that do not have a nucleus
and membrane-bound organelles
 Found in bacteria and archaebacteria
Prokaryotes
 Prokaryotic Cell Organelles:
 Nucleoid region –

part of the prokaryotic cell where the DNA is found
 Cell membrane –

innermost covering of the cell
 Cell wall –

outside of cell membrane
 Capsule –

outside of the cell wall, protective covering (not all
bacteria have it)
Prokaryotes
 Flagella (sing. Flagellum) –

long, whiplike structure that moves bacteria
 Pili –

short, hair-like projection used to stick to other surfaces
and for conjugation (exchange of genetic materials between
bacteria)
 Cytoplasm –

jelly-like fluid that dissolves substances and holds
organelles
 Ribosomes –

organelles that make proteins in the cytoplasm
Prokaryotes
Eukaryotes
 Protists, Fungi, Plants, and Animals
 Have nucleus and membrane-bound organelles
 Much larger and more complex than prokaryotic cells.
 Reproduce sexually and asexually
Eukaryotic organelles
 Nucleus
 Control center of cell; contains most of the cell’s DNA
 Nucleolus
 Location where ribosomes are synthesized
 Nuclear pore
 Allows RNA to move in and out of nucleus
Eukaryotic organelles
 Ribosomes
 Protein synthesis
 Rough ER
 Comprised of a network of tubes and flattened sacs;
Continuous with plasma membrane and nuclear
membrane
 Site of protein synthesis (consists of ribosomes) and used
for transport
Eukaryotic organelles
 Smooth ER
 Synthesis of membrane lipids and detoxification of drugs
 Involved in transport.
 No ribosomes
 Golgi Apparatus
 Connected with rough ER; flattened disc-shaped sacs,
stacked one on top of the other
 modification, storage, and packaging of proteins.
 “tags” proteins so they go to the correct destination.
Eukaryotic organelles
 Lysosomes (in animal cells and some protists)
 Digestion of nutrients, bacteria, and damaged
organelles
 Vacuoles
 Large sac-like membrane that stores materials like water,
salts, proteins, and carbohydrates.
 Large, single vacuole in plants; small, numerous
vacuoles in animals.
Eukaryotic organelles
 Chloroplasts
 Conversion of light energy to chemical energy of sugars
(site of photosynthesis)
 Bound by double membrane
 Mitochondria
 Conversion of chemical energy of food to chemical
energy of ATP (site of cell respiration)
 “Power House” of cell
 Bound by double membrane
Mitochondria
Eukaryotic organelles
 Cytoskeleton
 Gives cells their shape and internal organization and
helps in movement. Includes:



Flagella- long, whip-like structure used for movement
Cilia- short, hair-like structure used for movement
Centrioles- type of microtubule only found in animal cells
involved in cell division.
Eukaryotic organelles
 Cell membrane
 Regulates what goes in and out of the cell (we will study
this more soon!)
 Cell wall
 Support, shape, and protect the cell.
 Found in plant cells only!