Chapter 4 Notes Cell Physiology Biology Hamilton Science Department
Homeostasis Organisms must maintain a balance of materials that enter and leave their cells. Without this ability, they will die.
The Cell (Plasma) Membrane The property of a membrane to allow only certain particles through while keeping others out is known as selective permeability. One way cells maintain homeostasis is by having a selectively permeable cell membrane.
PASSIVE TRANSPORT- no energy required #1 DIFFUSION: THE MOVEMENT OF PARTICLES FROM HIGHER CONCENTRATION TO AN AREA OF LOWER CONCENTRATION
Diffusion occurs with CONTINUOUS MOVEMENT until EQUILIBRIUM is reached EQUILIBRIUM: equal amounts of substance are on both sides of the cell membrane
PASSIVE TRANSPORT continued.. #2 OSMOSIS: DIFFUSION OF WATER MOLECULES THROUGH A SELECTIVELY PERMEABLE MEMBRANE.
3 TYPES OF SOLUTIONS AROUND A CELL (3 Possibilities for the Direction of Water Movement around a Cell) 1. ISOTONIC: CONCENTRATION OF DISSOLVED SUBSTANCES AND WATER SAME ON BOTH SIDES OF MEMBRANE 2. HYPOTONIC: CONCENTRATION OF DISSOLVED SUBSTANCES IS LOWER THAN IN THE CELL (high concentration inside the cell—cell swells) 3. HYPERTONIC: CONCENTRATION OF DISSOLVED SUBSTANCES IS HIGHER THAN IN THE CELL (low concentration inside the cell—cell shrinks)
Hypertonic Solution– Hypotonic Solution- Water moves out of the cell (Balloon shrivels) Water moves into the cell!! (Balloon overfull) If a cell is placed in a……. ISOTONIC SOLUTIONS ARE BALANCED !!
#3 FACILITATED DIFFUSION: Diffusion of substances from area of high concentration to area of low concentration with help of carrier proteins.
#4 DIFFUSION THROUGH ION CHANNELS Movement of ions ( Na+, K+, Cl-) through cell membrane by means of ion channel Ion Channel: a transport protein with a polar pore through which ions can pass –Some ion channels have gates that open/close –Channels are specific to a certain kind of ion
ACTIVE TRANSPORT * REQUIRES ENERGY* Energy used is from ATP MOVEMENT OF SUBSTANCES FROM LOW CONCENTRATION. TO ALREADY HIGH CONCENTRATION Opposite of Passive Transport Substances move AGAINST GRADIENT (or opposite of equilibrium)
Active Transport: #1 Ion Channel Pumps Uses ion channel (aka: carrier proteins)-allows sodium, calcium, and potassium ions to enter and leave the cell against gradient called Membrane Pumps Most noteable Ion Pump is the Sodium- Potassium Pump
Active Transport: #2 Endocytosis and Exocytosis For substances that are too big to be moved across cell membrance by carrier proteins Examples: Proteins and Polysaccharides
ENDOCYTOSIS: USE ENERGY TO TAKE IN LARGE PARTICLES. CELL SURROUNDS THE PARTICLES – Forms vesicle around particles.
EXOCYTOSIS: RELEASE OF WASTES FROM CELL VESICLE. VESICLE FUSES WITH MEMBRANE AND CONTENTS ARE RELEASED TO OUTSIDE.