Homeostasis How everything keeps from blowing up, falling apart, self-destructing, dying from diseases, and, in general, getting along fine from one day to the next Reading: Theme II – Chapter 4 Enzymes will be covered later

Diffusion Process by which particles spread out from high concentration to areas of low concentration Does NOT require energy (no ATP)

Concentration Gradient Name given to the difference in the amount of dissolved material in equal amounts of solvent (solute: kool aid, solvent: water)

Passive transport Interchangeable with “diffusion” Does NOT require energy Molecules move from high to low concentration

**Osmosis** Special kind of diffusion (NO ENERGY) Movement of WATER through a semi-permeable membrane Net movement of water is from high  low concentration of water (low  high concentration of solute)

Solution Types always a comparison! Isotonic:the concentration of solute in one solution is EQUAL to the concentration of solute in another solution (animal cells like this one)

Hypotonic: The solute concentration is lower (more water!) than in another solution (plants like, animals do not) Hypertonic: The solute concentration is higher (less water) than in another solution (no one really likes this!) (plasmolysis)

Important for cells and multicellular (people and animals) People: – Oxygen and carbon dioxide diffuse through lungs – Food nutrients are diffused through stomach and intestines into the blood – Nutrients in blood diffuses into muscles – Wastes in blood diffuse to kidneys Cells: – Nutrients diffuse into cells and wastes diffuse out

Active Transport Sometimes nutrients are scarce or Nutrients are too big to enter cell They have to go against the concentration gradient – This requires ENERGY called ATP Diffusion is like rolling downhill to get to food, active transport is running up the hill to get to food How does this work? We need to look at cell structure

CELLS and all their little bits The whole business of cells came about due to the invention of the MICROSCOPE

THREE POINTS TO THE CELL THEORY 1.The cell is the unit of structure of all living things 2.The cell is the unit of function of all living things 3. All cells come from pre-existing cells

EXCEPTIONS to the cell theory 1.Some cells lack nuclei (red blood cells) 2. Certain organelles can replicate without help from the nucleus (mitochondria, chloroplasts)

Exceptions, continued 3.Some organisms lack the separations that divide the organism into cells 4. Where did the first cell come from? 5. *** Viruses contain genetic material but can only reproduce when they parasitize another cell (AIDS)-- pathogenic

CELLS AND ALL THEIR LITTLE BITS…

Organelles Internal structures of a cell Each performs a specific function necessary for survival

Cell Wall ONLY IN PLANT CELLS outside of the cell membrane Made of cellulose (roughage-polysaccharide) Gives shape and support

Cell Membrane In charge of regulating what goes in/out of the cell

Cytoplasm In all living cells Is 75% water Site of most chemical reactions Includes inorganic molecules, organic molecules, surrounds the organelles

Endoplasmic Reticulum A continuous network of internal membrane channels Used for intracellular transport In all eukaryotic cells Associated with storage, synthesis, and transport of substances within the cell

Two Types of ER Rough ER- has ribosomes attached Smooth ER- no ribosomes attached

Ribosomes Site of protein synthesis Either free floating or attached to the ER Made up of RNA and protein

Golgi Bodies/Apparatus Stack of flattened membrane bound sacs Used for packaging materials for secretion Makes lysosomes

Lysosomes Membrane-bound sacs filled with hydrolytic enzymes Fuses with food vacuoles to deliver digestive enzymes

Mitochondria Site for aerobic cellular respiration Makes ATP Has its own genetic material (DNA) for self- replication

Chloroplasts ONLY IN PLANT CELLS Site of photosynthesis Turns CO 2 and H 2 0 into C 6 H 12 O 6

Vacuoles and Vesicles Fluid filled organelles surrounded by membrane Plants have large central vacuole used to store water, sap, waste, toxins, etc.

Microfilaments, microtubules Long thin tubes of proteins Involved in the movement of chromosomes during cell division Is what cilia, flagella and centrioles are composed of

Cilia and Flagella Used for locomotion Cilia—small, hairlike projections – In our respiratory tract and in female reproductive tract Flagella—long, whiplike projections – sperm

Centrosome with centrioles ONLY IN ANIMAL CELLS Involved in cell division (mitosis)

Nucleus Contains the genetic material that directs the activity of the cell Only in eukaryotic cells Has a double membrane-nuclear envelope Contains the nucleolus

Nucleolus A dark staining body within the nucleus Site of ribosome synthesis

Cell Transport (how stuff goes in/out/round and round

Cell Membrane or Plasma Membrane Called “semi-permeable” or “selectively permeable” as it regulates the transport of materials in/out of the cell Surrounds all cells

Made up on a phospholipid bilayer with embedded proteins— “fluid mosaic model” Maintains internal homeostasis Water, carbon dioxide, oxygen pass through easily, larger molecules do not

Active transport and proteins Proteins in the cell membrane: – Allow larger chemicals in or out of the cell – Allow chemicals to move against concentration gradient

Extra information after this slide Other forms of active transport

Endocytosis Method for taking in molecules too large for diffusion Requires energy

Phagocytosis When a cell engulfs undissolved large particles…results in a food vacuole

Pinocytosis When a cell engulfs dissolved large particles

Exocytosis Requires ATP Used to release molecules too large to pass through the membrane via diffusion

A vacuole or vesicle fuses with the membrane and opens to the cell’s environment Food vacuoles remove wastes, contractile vacuoles remove excess water

Cyclosis Natural streaming of cytoplasm within all cells Used for intracellular transport