 Keeping an organism’s internal environment stable  Examples Temperature Blood pressure pH 60% H 2 O Water balance

 Help the organism respond to stimuli and maintain homeostasis on a large scale (whole body) 1. Negative Feedback 2. Positive Feedback

 When a situation causes a response that reverses the first condition  Most common in the body normal body temp skin cells detect cold brain gets message response shiver, blood vessels constrict and lower blood flow to the skin

normal blood glucose level Blood glucose level falls Soon after a meal Long after a meal Blood glucose level rises normal blood glucose level Liver converts glycogen to glucose Too High Pancreas secretes insulin Too Low Pancreas secretes less insulin Liver coverts glucose to glycogen

 When a situation causes a response that amplifies (increases) the initial (1st) condition  Ex. Labor pains, milk production, digestive enzymes enzymes enzymes enzymes enzymes enzymes enzymesenzymes enzymes enzymes

On a small scale, individual cells maintain homeostasis by controlling what gets into and out of a cell.

 Cells move molecules in and out 2 ways: 1. PASSIVE TRANSPORT: does not use energy, moves from high to low concentration. 2. ACTIVE TRANSPORT: uses energy, moves from low to high concentration.

***Molecules move with the flow, from high to low concentrations. ***No Energy Required! ***3 Types: Diffusion Facilitated Diffusion Osmosis

 Diffusion: movement of anything from high to low concentration.

 Facilitated Diffusion: Movement of molecules from high to low concentration.  A protein in the membrane helps make bigger spaces in the membrane.

Facilitated Diffusion Movement of larger molecules (ex. glucose) from high concentration to low concentration with the help of a carrier protein inside cell outside cell

 Osmosis: movement of water from high to low concentration across a membrane.

Osmosis Movement of WATER from high concentration to low concentration diffusion with WATER * When the cell is at equilibrium with its environment, equal amounts of its environment, equal amounts of water move into and out of the cell water move into and out of the cell 60% H 2 O ISOTONIC SOLUTION

* When there is more water in a cell than outside of a cell, water will leave the cell outside of a cell, water will leave the cell 2% H 2 O 75% H 2 O this can cause a cell to shrink this can cause a cell to shrink HYPERTONIC SOLUTION

* When there is more water outside a cell than inside of a cell, water will enter the than inside of a cell, water will enter the cell cell 80% H 2 O 60% H 2 O this can be bad, if too much water this can be bad, if too much water enters then the cell may lyse (burst) enters then the cell may lyse (burst)CYTOLYSIS HYPOTONIC SOLUTION

Plant cells respond differently to osmosis because of their cell wall * When water leaves a plant cell, the cell wall’s shape does not change, but the cell membrane shape does not change, but the cell membrane pulls away and creates an air pocket between pulls away and creates an air pocket between the two. This causes the plant to WILT. the two. This causes the plant to WILT. 85% H 2 O 5% H 2 O This is called PLASMOLYSIS

* When water enters a plant cell, the cell membrane pushes against the cell wall and membrane pushes against the cell wall and creates pressure. creates pressure. 85% H 2 O 98% H 2 O This is called TURGOR PRESSURE

 Move molecules against the flow, from low to high concentration.  Uses ENERGY!

 For Multicellular Organisms:  Uses a carrier protein, to carry them across the membrane

Active Transport For Unicellular Organisms VESICLE --> organelle that transports materials through, into, or out of a cell * ENDOCYTOSIS --> into the cell Pinocytosis --> fluids Phagocytosis --> foods vesicle

* EXOCYTOSIS --> out of the cell

 Smallest unit of life that can carry on all processes of life  Unicellular or multicellular  Multicellular organization cells  tissues  organs  organ systems cell tissue organ organism A group of similar cells is called a tissue. A group of similar tissues is called an organ. A group of organs working together form an organ system or organism

CELL THEORY  All living things are made of one or more cells  Cells are an organisms’ basic unit of structure and function  Cells only come from preexisting cells (mitosis) The scientist Schwann, Schleiden, and Virchow contributed to what we call today the …

THERE ARE TWO TYPES OF CELLS:  Prokaryotic  Eukaryotic  YOU ARE EUKARYOTIC!

Prokaryotic  DOES NOT have membrane bound nucleus – – DOES NOT have organelles with a membrane – –Smaller cells – –ALWAYS unicellular

A prokaryotic cell 1. Ribosomes 2. DNA 3. Plasma membrane 4. Cell wall

Eukaryotic – –HAS a membrane bound nucleus – –HAS organelles with a membrane – –LARGER cells – –Unicellular or multicellular

A eukaryotic cell 4. Plasma membrane 1. Nucleus 2. Nucleolus 3. Chromosomes 5. Organelles Chapter Assessment