Cells

Levels of cellular organization Atom Molecule Organelle Cell Tissue Organ 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 Cytoskeleton 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 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 Cell Wall 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 Ribosomes 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 shapes 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 rRNA) which work together to synthesize protein Located throughout the cytoplasm

External Layers Cell Membrane Cell Wall Glycocalyx 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 Fimbriae Conjugation Pili 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