Keeping an organism’s internal environment stable

Examples

Temperature

Blood pressure

pH

6060% %

HH22OO

6060% %

HH22OO

Water balance

Help the organism respond to stimuli and maintain homeostasis on a large scale (whole body)

1. Negative Feedback2. Positive Feedback

When a situation causes a response that reverses the first condition

Most common in the body

normal body normal body temptemp

skin cells skin cells detect colddetect cold

brain gets brain gets messagemessage

responseresponse

shiver, blood shiver, blood vessels constrict vessels constrict and lower blood and lower blood flow to the skinflow to the skin

normal normal blood blood

glucose glucose levellevel

Blood glucose Blood glucose level fallslevel fallsSoon Soon

after after a a

mealmeal

Long Long after after

a a mealmeal

Blood Blood glucose glucose

level riseslevel rises

normal normal blood blood

glucose glucose levellevelLiver

converts glycogen

to glucose

Too Too HigHighh

PancreaPancreas s

secretes secretes insulininsulin

Too Too LowLow

Pancreas Pancreas secretes secretes

less insulinless 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

enzymenzym

eses

enzymenzymeses

enzymenzymeses

enzymenzymeses

enzymenzymeses enzym

enzym

eses

enzymenzymeses

enzymenzym

eses

enzymenzymeses

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: DiffusionFacilitated DiffusionOsmosis

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 DiffusionFacilitated DiffusionMovement of larger molecules Movement of larger molecules (ex. (ex. glucose) glucose) from high concentration to low from high concentration to low concentration with the help of a carrier concentration with the help of a carrier proteinprotein

inside cellinside cell

outside celloutside cell

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

OsmosisOsmosisMovement of Movement of WATERWATER from from highhigh concentration concentration to lowto low concentration concentration

diffusion with WATERdiffusion with WATER

* * When the cell is at equilibrium When the cell is at equilibrium withwith its environment, its environment, equal amounts equal amounts ofof water move into and out of the water move into and out of the cellcell

60% 60% HH22OO

60% 60% HH22OO

ISOTONIC SOLUTIONISOTONIC SOLUTION

* * When there is more water in a cell thanWhen there is more water in a cell than outside of a cell, outside of a cell, water will leave the water will leave the cellcell

2% 2% HH22OO

75% 75% HH22OO

this can cause a cell to shrinkthis can cause a cell to shrink

HYPERTONIC SOLUTIONHYPERTONIC SOLUTION

* * When there is more water outside a cellWhen there is more water outside a cell than inside of a cell, than inside of a cell, water will enter thewater will enter the cellcell

80% 80% HH22OO

60% 60% HH22OO

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)

CYTOLYSISCYTOLYSIS

HYPOTONIC SOLUTIONHYPOTONIC SOLUTION

Plant cellsPlant cells respond differently to respond differently to osmosis because of their osmosis because of their cell wallcell wall

* When water leaves a plant cell, the cell wall’s * When water leaves a plant cell, the cell wall’s shape does not change, but the cell shape does not change, but the cell membranemembrane pulls away and creates an air pocket between pulls away and creates an air pocket between the two. This causes the plant to the two. This causes the plant to WILTWILT..

85% H2O

5% H2O

This is called This is called PLASMOLYSISPLASMOLYSIS

* When water enters a plant cell, the cell * 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% H2O

98% H2O

This is called This is called TURGOR TURGOR PRESSUREPRESSURE

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 TransportActive TransportFor Unicellular OrganismsFor Unicellular Organisms

VESICLEVESICLE --> organelle that transports --> organelle that transports materials through, into, or out of a cellmaterials through, into, or out of a cell

* * ENDOCYTOSISENDOCYTOSIS --> into the cell --> into the cell

Pinocytosis --> fluidsPinocytosis --> fluids

Phagocytosis --> foodsPhagocytosis --> foods

vesiclevesicle

* * EXOCYTOSISEXOCYTOSIS --> out of the cell --> 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

tissueorgan

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 THEORYCELL 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:THERE ARE TWO TYPES OF CELLS:

1.1. ProkaryoticProkaryotic

2.2. EukaryoticEukaryotic

YOUYOU ARE ARE EUKARYOTIC!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