The Cell

Standard/Obj Know how prokaryotic cells, eukaryotic cells, and viruses differ in complexity and general structure. Know the role of the Endoplasmic Reticulum and Golgi apparatus in the secretion of proteins. Know cells are enclosed w/in semipermeable membranes that regulate their interaction w/ their surroundings.

Cell Intro *celltissueorgansystem Cell-smallest unit that can carry on all the processes of life. Unicellular or Multicellular Organelle:--cell component that performs specific functions in cell Eukaryote:-cell membrane, nucleus, membrane bound organelles Prokaryote-cell membrane, few non-membrane bound organelles, genetic material -no nucleus -ex. bacteria (DNA and ribosomes)

Robert Hooke-1665 Observed a slice of cork, holes, “little boxes” Observed stems of trees, carrots, and again noticed little boxes Named the “cell” Anton van Leeuwenhoek-1675 Observed living cells Made microscopes

More Research: Mathias Schleiden-1838, all plants made of cells Theodor Schwann-1839, all animals made of cells Rudolph Virchow-1855, cells come only from other cells

Cell Theory All living things are composed of one or more cell Cells are organisms’ basic units of structure & function Cells come only from existing cells

Cell (Plasma) Membrane Shape and flexibility to cell Maintains homeostasis Semi-permeable membrane or selective permeability Phospholipid bilayer-2 layers, made up of lipids-fatty acid chains-(water insoluble) and phosphate groups (water soluble) Cell is exposed to water inside and outside

Fluid Mosaic Model: flexible, proteins make pattern Phosphate Heads Lipid Tails Integral Proteins (A) extend across the entire membrane and are exposed to the inside and outside -Transport Proteins: some form channels or pores through which certain substances can pass

Exposed proteins often have carbohydrates (E) attached to them Exposed proteins often have carbohydrates (E) attached to them -hold other cells or act as sites where viruses or chemical messengers can attach Peripheral proteins (C) are located on the interior and exterior surface

Cholesterol Helps to stabilize phospholipids Prevents fatty acid chains from sticking together

Cell Wall Made of cellulose Plant cells, fungi, most bacteria Rigid structure on the outside of cell membrane Provides support and protection

Cytoskeleton Maintains shape & support Helps organelles move w/in cell Located under cell membrane Not membrane bound Microtubules: thin, hollow protein tubes; cell division Microfilaments: fine, threads called actin; muscle contraction

Movement Cilia Short, hairlike extensions on the surface of some cells Helps in movement of the cell Ex. human respiratory tract: helps move mucus that traps dust and bacteria Flagella Whiplike, longer than cilia, single or in pairs Moves by whipping back and forth Ex. sperm cell *Both cilia and flagella made of microtubules

Cytoplasm Clear, jellylike material that fills the cell Contains cytosol & organelles in the cell Cytosol-made up of water, salts, organic molecules, & enzymes Maintain shape, provide suspension to organelles Store chemicals

Cell Organelles Nucleus Nuclear envelope (2) w/ pores, phospholipid bilayer Nucleic acids (DNA, RNA) made here Chromatin made up of DNA (stores genetic info) Directs cell activities, includes making proteins

Nucleolus Located in nucleus Makes ribosomes (made of proteins and RNA)

Ribosome Not membrane bound Where proteins are assembled Receives directions from nucleus (DNA)

ER-Endoplasmic Reticulum (highway) Membrane system of folded sacs and connected vesicles Rough ER -covered with ribosomesproteins are exported or inserted inside the cell membrane -proteins leave in vesicles to the golgi

-synthesis of steroids, lipids -calcium storage 4. Smooth ER -few or no ribosomes -synthesis of steroids, lipids -calcium storage -breakdown of toxic substances by liver cells

Golgi Apparatus (Golgi Bodies) Sorts proteins, packages and secretes (sends it outside cell) Flattened stacks of membranes filled with fluid and dissolved substances Analogy: factory assembly line, post office proteinrough ERGolgioutside (ribosome) (vesicle) (vesicle)

Mitochondrion (-a) *mighty mouse, battery 1. 2 membranes -smooth outer membrane serves as boundary -inner membrane has many folds (cristae) that increase the internal surface area and energy-storing molecules made here -matrix: internal fluid

2. Have own DNA 3. Site of chemical rxns that transfer energy from organic compounds to ATP (Adenosine Triphosphate) 4. Numerous in cells that have high energy needs ex. liver, muscle

Lysosome *trash can contains digestive enzymes that digest food particles, bacteria, & worn out/broken parts of cells small, spherical primarily in animal and fungal cells rare in plant cells

Plant Cells Cell Wall Vacuoles -temporary storage -small in animal cells -stores food, enzymes and waste products -takes up as much as 90% of volume of cell 3. Plastids -store starches, lipids, or pigments (absorb visible light) -has 2 membranes and DNA

-has green pigmentchlorophyll -chromoplasts: make and store pigments 3. cont’d -chloroplasts -each encloses a system of flattened, membranous sacs called thylakoids (capture light energy) convert into chemical energy to make food -has green pigmentchlorophyll -chromoplasts: make and store pigments -leukoplasts: store food such as starches & proteins ex. potato