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 4Enzymes 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 Typesalways 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 scarceor

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

http://www.cytochemistry.net/Cell-biology/cit3.htm

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 CO2 and H20 into C6H12O6

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