Cells

Bio 1Mr. Hellmer

What is a cell?

• Basic functional, structural, and biological unit of all known living organisms.

• Surrounded by a membrane (lipid bilayer)• Cells can replicate independently (cells only

come from other cells)• Building blocks of life

Cell Theory

– All living things are made of one or more cells– Basic unit of structure and function in organisms– Cells come only from the reproduction of existing

cells

DiversitySize, shape, and internal organization varies– Humans have at least 200 different cell types– Volume grows faster than surface area• Surface allows for passage of materials

– Shape enables function

Nerve Cell Red and White Blood Cells

• All cells are surrounded by a Cell Membrane• Not all cells are the same inside:– Eukaryotes - have membrane bound nucleus – Prokaryotes- no membrane bound nucleus or

membrane bound organelles

Eukaryotic Cell Prokaryotic Cell

• Prokaryotes– Simple organization– No membrane bound

organelles– No membrane bound nucleus– Can have a cell wall– Usually circular DNA– Unicellular

Examples:Bacteria (Escherichia coli & Staphylococcus aureus)Archaea (Halobacteria)

Halobacteria (Archaea) E. Coli (Bacteria)

• Eukaryotes– Complex organization– Membrane bound

organelles– Membrane bound nucleus– Linear DNA– Multicellular and unicellular Examples:

Plants, animals, fungi, protists

Prokaryotes and Eukaryotes• Prokaryotes

– Simple organization– No membrane bound organelles– No membrane bound nucleus– Can have a cell wall– Usually circular DNA– Unicellular

• Eukaryotes– Complex organization– Membrane bound organelles– Membrane bound nucleus– Linear DNA– Multicellular and unicellular

Prokaryote

Eukaryote

Eukaryote vs. Prokaryote

Cell Parts • Prokaryotes and Eukaryotes

– Cell (plasma) membrane– Cell wall (bacteria and plants)– Cytoplasm – Ribosomes– Flagella– DNA– RNA

• Eukaryotes– Nucleus– Nuclear envelope– Nucleolus– Mitochondria– Endoplasmic Reticulum– Golgi apparatus– Lysosome– Vacuole– Cytoskeleton– Centriole– Cilla and Flagella– Chloroplast– Cell Wall– Central Vacuole

Cell (plasma) Membrane

• Allows substances to pass into and out of the cell– Known as selectively permeable

• Made primarily of lipids and proteins– Phospholipid bilayer– Proteins are attaching site for signals and also allow passage of

molecules

Organelles

• Internal functional structures of a cell• Prokaryotes only have ribosomes• All others are in Eukaryotes

Nucleus

• Stores DNA (hereditary information)

• Surrounded by nuclear membrane and nuclear envelope

• Where RNA is copied from DNA– RNA passes through nuclear pores

(small holes in nuclear envelope)• Contains chromatin (DNA and

protein) which coil up when the cell will divide into chromosomes

Nucleolus

• Located in the nucleus• Where ribosomes are made

Cytoplasm

• Between cell membrane and nucleus • Contains:

• cytosol (gelatin-like fluid)• organelles, salts, minerals, and organic molecules

Mitochondria

• Where ATP (energy) is made from glucose (cell respiration)– Drives chemical reactions in a cell

• Powerhouse of cell• More energy use, more mitochondria• 2 membranes

– Outer membrane is barrier – Inner membrane has folds (cristae) that

increase surface area where reactions occur• Have their own DNA

– Grow and divide only from other mitochondria

Endoplasmic Reticulum

• Synthesis and transport of molecules inside cell (cellular highway)

• Two types of ER:– Rough ER has ribosomes on it

• More in cells that make a lot of proteins

– Smooth ER doesn’t have ribosomes• Makes steroids (gland cells)• calcium (muscle cells)• breakdown toxins (liver cells)

• Both types may be continuous with each other

Golgi Apparatus

• Processing, packaging, and secreting of molecules

• “UPS” of cell• Works with ER

Lysosome

• Small spherical vesicle containing enzymes• Digests proteins, carbohydrates, lipids, DNA,

and RNA, old organelles, viruses, bacteria• Garbage disposal of cell• Rare in plants• #12

Ribosome

• Composed of protein and RNA (no membrane)– Packaged from the

nucleolus• Synthesis of proteins– Free ribosomes in the

cytoplasm – proteins for the cell

– Ribosomes on Rough ER – proteins for export

Cytoskeleton

• Long protein strands that maintain the shape of the cell

• Microfilaments – Smallest strands – Movement of cell and

contraction of muscle cells • Microtubules (hollow tubes)

– Largest strands– Organized by centrosome– Form spindle fibers for cell

division

Cillia and Flagella

• Part of the cytoskeleton• Cilia is short and numerous– On many unicellular

(movement)– Also on some multicellular

• Example: respiratory cells

• Flagella is a long and less numerous– Example: 1 flagella on sperm

cells

Centriole

• Make up centrosome• Organizes

microtubules (mitotic spindle during cell division)

• Not present in plants

Plant Cells

• Cell Wall surrounds cell membrane– Causes rigidity,

• Central Vacuoles store enzymes and metabolic wastes– May take up to 90% of cell– May be toxic which provide defense

• Plastids – contain DNA and store starch or pigments

(which absorb light)– Chloroplast: which contain thylakoids (sacs)

• Chlorophyll and Carotenoids• Photosynthesis

Cell TransportPassive Transport across a membrane-Does NOT require energy-Moves down the concentration gradient, from high to low-Diffusion, Osmosis, Facilitated Diffusion Active Transport across a membrane-Moves up the concentration gradient, from low to high-Requires energy-Sodium–Potassium Pump, Endocytosis, Exocytosis Osmosis and how cells react in different conditions- Outside of cell has lower concentration of solute than inside = water diffuses in- Outside of cell has higher concentration of solute than inside = water diffuses out- Outside of cell has equal concentration of solute to inside = water diffuses in and out