Cells

Levels of cellular organization

Atom MoleculeOrganelleCellTissueOrganOrgan SystemOrganism

Cells

Prokaryotic

Bacteria

Eukaryotic

Animal Plant

Division of Cells

Eukaryotic Cells Literally means “True nucleus”

Have a nucleus Complex Cells Have membrane-bound organelles Organisms made of eukaryotic cells are called

“eukaryotes”Examples: Animals, Plants, Fungi, Unicellular organisms like paramecium and amoeba

Cellular Components

Cytoplasm Gel-like substance within the cell

where organelles are foundCytoskeleton

“Cell skeleton” Network of protein fibers that

maintain the shape of cell Composed of three networks of fibers

1. Microtubules: largest; hollow tubes made of protein; determine cell shape; scaffolding

2. Intermediate Filaments: Provide strength of cell

3. Actin Filaments: smallest; contractile string-like proteins that allow for cell movement

Cellular Components

Cell Membrane Semi-permeable barrier that

encloses the cell Regulates what enters and exits

the cell Provides protection Found in all types of cells

Cell Wall Porous, rigid barrier found

surrounding the cell membrane Adds additional layer of support

and protection Not found in animal cells

Organelles

Nucleus Houses the genetic

material (DNA) needed for replication of the cell

“Control Center” of the cell Contains the instructions

for the creation of proteins (made from DNA)Exterior: Surrounded by nuclear envelope: double-layered

membrane that encloses the DNA; contains nuclear pores: small openings that allow for the passage of molecules between the cytoplasm and the nucleus

Interior: DNA in the form of chromatin (string-like)• Nucleolus: where ribosomes are made; very dense region

Organelles

Endoplasmic Reticulum A grouping of sac-like

structures Two Types of ER:

Rough ER: contain ribosomes (creating ‘rough’ appearance); involved in the process of protein synthesis

Smooth ER: no ribosomes; involved in lipid synthesis

Ribosomes Location where proteins are

made (protein synthesis)

Organelles

Golgi Apparatus Looks like a stack of membranes (pancake-like

appearance) Modifies, sorts and packages proteins received from

the ER. Break off from the golgi apparatus; floats freely in the

cell or travels to cell membrane where it will eventually exit the cell.

Creation of lysosomes

Organelles

Lysosomes Contain enzymes necessary for digestion of cell food

or waste Can break down lipids, carbs, proteins Digest non-functional organelles, ‘cleaning up’ the cell

Organelles

Vacuoles Sac-like structure responsible for storage of various

materials (e.g. water, carbs, proteins, etc.)

Organelles

Mitochondria The “Powerhouse” of the cell Convert food energy into energy that is used by the

cell itself (for growth, development, movement, etc.) via cellular respiration ATP (Adenosine Triphosphate)

Complex structure

Organelles

Chloroplast Site of photosynthesis

Energy from sun is captured and converted into chemical energy

Contain the pigment chlorophyll which absorbs solar energy used in photosynthesis Responsible for the green

color of plants

Organelles

Centrioles Made of microtubules Located near nucleus Organize microtubules within the cytoskeleton prior

to cell division

Division of Cells

Prokaryotic Cells Include Bacteria & Archaea Literally means “before nucleus”

So-have no nucleus Lack membrane-bound organelles Simpler and much smaller than Eukaryotes Organisms made of prokaryotic cells are called

“prokaryotes”

Structure of Prokaryotes

Three basic shapes1. Bacilli: rod-shaped bacteria2. Cocci: Spherical-shaped bacteria3. Spirilla: Spiral-shaped bacteria; flexible

Prokaryotic Cell Parts: Interior

Do prokaryotic cells have DNA if they lack a nucleus?

Nucleoid: a region within the cytoplasm of the cell in which the DNA is located; center of the cell (no membrane encloses the DNA)

Cytoplasm Semifluid, gel-like solution

encased within the cell membrane of the cell

Interior

Ribosomes Made of two subunits

(each containing a combination of various proteins and rRNA) which work together to synthesize protein

Located throughout the cytoplasm

External Layers

Cell Membrane Regulates the entrance

and exit of various substances in and out of the cytoplasm

Cell Wall Provides shape,

structure, and support for cell

Glycocalyx The outermost layer of

bacterial cells; gel-like protective layer

External Structures

Flagella Allows for cell movement Long, rotating filament that

propels the cell forwardFimbriae

Hair-like bristles located on the external surface of the cell

Allow cells to attach to surfaces

Conjugation Pili Tube-like structures that

allow for bacteria to pass DNA from cell to cell; usually larger and less numerous than fimbriae