Homeostasis and Transport (BIO.A.4)

The Balancing Act of Life Homeostasis – process by which an organisms maintains a relatively stable internal environment Examples: –Thermoregulation – maintaining body temperature –Water regulation – keeping enough water in your body –Regulating oxygen, blood sugar, and blood pH

Various methods of thermoregulation

Plasma Membrane Function: The plasma membrane encloses the cell and protects it. Function: It lets certain particles into and out of the cell. Surrounds all cells

MOVEMENT THROUGH THE PLASMA MEMBRANE How do materials or substances enter or leave cells?

THE PLASMA MEMBRANE IS PICKY! Selective Permeability - the membrane can pick and choose what particles can pass through it.

PLASMA MEMRANE Plasma membranes are made of phospholipids, proteins, and sometimes cholesterol.

THE PHOSPHOLIPID A phospholipid - made up of a glycerol attached to 2 fatty acids and a phosphate group. The fatty acids are hydrophobic (hate water). The phosphate group is hydrophilic (likes water).

Reference

THE BILAYER STRUCTURE The plasma membrane is a bilayer of phospholipids.

THE BILAYER STRUCTURE The plasma membrane is a bilayer of phospholipids. Reference

OTHER STRUCTURES IN THE MEMBRANE... Animal plasma membranes have cholesterol in between phospholipids to slow their movement.

MEMBRANE PROTEINS Proteins are embedded in membranes. Some are on the inner or outer surfaces, some go the entire way through the bilayer.

MEMBRANE PROTEINS’ JOBS Regulate which particles can pass through membrane (transport) Act as enzymes in chemical reactions Act as markers on outside and inside of cell to identify self

WAYS TO MOVE THROUGH THE MEMBRANE: 1. Active transport requires energy to move the molecules through the plasma membrane. 2. Passive transport does not require energy, and occurs spontaneously.

PASSIVE TRANSPORT Types of passive transport –Diffusion –Osmosis –Facilitated diffusion

DIFFUSION Diffusion is the movement of molecules from a HIGH concentration to a LOW concentration. Diffusion occurs when a system is not at equilibrium and there is a difference in concentrations.

Reference

FACTORS THAT AFFECT DIFFUSION: Temperature - higher temperature means more energy and molecules will diffuse faster. Size - Smaller molecules will move more rapidly than larger molecules

REAL-LIFE EXAMPLES CO 2 and O 2 diffuse across plasma membranes. Oxygen moves from an area of high concentration to an area of low concentration from your lungs to your blood to your cells. As chemical reactions in the cell use up oxygen they produce CO 2. The concentration of CO 2 inside the cell increases so that more CO 2 is inside of the cell. Therefore CO 2 diffuses into your blood and then into your lungs were it is exhaled.

OSMOSIS The movement of water from a high concentration to a low concentration. It is the diffusion of water. This can cause cells to burst or shrink.

OSMOSIS IN PLANT AND ANIMAL CELLS In saltwater, animal cells shrivel and plant cells show plasmolysis (the insides of the cell shrivel, but not the cell wall). In freshwater, animal cells burst and plant cells swell, but do not burst due to large vacuoles and the cell wall.

Osmoregulation Saltwater organisms have to get rid of salt and conserve water. Freshwater organisms have to get salt and get rid of excess water.

FACILITATED DIFFUSION Helping diffusion along Proteins help certain chemicals pass through a plasma membrane Requires no energy (still moves from high to low) Usually needed for slightly larger molecules like glucose

High Concentration Low Concentration Cell Membrane Glucose molecules Protein channel

High Concentration Low Concentration Cell Membrane Glucose molecules Protein channel

ACTIVE TRANSPORT When a cell needs energy to move molecules from low to high concentration. Proteins pump molecules through membrane Molecules move against diffusion (from low to high concentration)

Reference

OTHER WAYS CELLS GET MATERIALS... Vesicles – a membrane-bound sac that is used to transport materials inside of a cell Endocytosis – the plasma membrane engulfs and takes in materials and puts them into a vesicle Exocytosis – vesicles with chemicals move to plasma membrane and fuse with membrane. The chemicals are then released.

Exocytosis Reference

ORGANELLES AND TRANSPORT Some organelles are involved in moving materials within a cell. For example, proteins that are made in a ribosome often enter the rough ER. The rough ER may modify the protein and transports it to the Golgi apparatus for processing and packaging. The protein is packaged in a vesicle (sac) and delivered to where it is needed.