Chapter 4 Notes Cell Physiology Biology Hamilton Science Department.

Chapter 4 NotesChapter 4 NotesCell PhysiologyCell Physiology

Chapter 4 NotesChapter 4 NotesCell PhysiologyCell Physiology

Biology Biology

Hamilton Science Hamilton Science DepartmentDepartment

HomeostasisHomeostasis• Organisms must

maintain a balance of materials that enter and leave their cells.

• Without this ability, they will die.

The Cell (Plasma) The Cell (Plasma) MembraneMembrane

• 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.

The Plasma MembraneThe Plasma Membrane

PASSIVE PASSIVE TRANSPORT-TRANSPORT-

no energy requiredno 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–

HypotonicSolution-

Water moves outof the cell(Balloon shrivels)

Water movesinto 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: Active Transport: #1 Ion Channel Pumps #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.