Cells Levels of cellular organization Atom Molecule Organelle

Cells

Levels of cellular organization �Atom �Molecule �Organelle �Cell �Tissue �Organ System �Organism

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 found �Cytoskeleton “Cell skeleton” Network of protein fibers that maintain the shape of cell Composed of three networks of fibers 1. 2. 3. Microtubules: largest; hollow tubes made of protein; determine cell shape; scaffolding Intermediate Filaments: Provide strength of cell 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 plants for the green color of

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 shapes 1. 2. 3. Bacilli: rod-shaped bacteria Cocci: Spherical-shaped bacteria 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 r. RNA) 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 forward � Fimbriae 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