BIO Lab 1 Diffusion and Osmosis

plasma membrane

regulate movement of substance into an out of the cell

-maintaining homeostatic state of cell

-phospholipid bilayer and specialized proteins

selectively permeable

unique structure of the plasma membrane allows it to be

-permeability depends on size, charge, lipid solubility and its concentration as well as external factors like temperature and pressure

Passive Transport

essential substances (oxygen and water) through the plasma membrane; no cellular energy (ATP)

Types of passive transport

diffusion, facilitated diffusion, filtration, and osmosis

Diffusion

passive transport: random movement of molecules from regions of greater concentration to regions of lesser concentration

Brownian motion

diff-usion: random movement of molecules from regions of greater concentration to lesser concentration until equilibrium

equilibrium

attained when equal distribution of molecules exists throughout the system

facilitated diffusion

carrier proteins along the cell membrane are required to carry specific molecules (like glucose) across the membrane into the cell

Filtration

hydrostatic pressure (water pressure) forcing molecules through a cell membrane.

-takes place in kidneys in formation of urine

Osmosis

passive transport: diffusion of water across semi-permeable membrane

solution

passive transport: solute + solvent

Tonicity

refers to the concentration of solute in the solvent

Hypotonic

Osmosis: lower concentration of solute relative to inside the cell

-water will rush into the cell in am attempt to reach equilibrium

-bursting of cells in this state is called cytolysis or osmoticlysis

hypertonic

Osmosis: higher concentration of solute relative to inside of the cell

-water will be drawn out of cell to reach equilibrium

-crenation in red blood cells and plasmolysis in plant cells

Turgor pressure

In plants, the swelling of cells placed in a hypotonic solution

-The framework cell wall protects the cell from bursting.

- keeps the plant erect. If the turgor pressure is lost in a plant, the plant will wilt. Just think of the plants in your yard on a hot summer day.

isotonic

solution contains the same concentration of solutes as the inside of a cell

-in plasma, water will move into or out red blood cell until equilibrium is established

-red blood cells are typically in this state

Active Transport

into or out of a cell occurs when the substance is to be moved from an area where the substance is present in a relatively low concentration to an area where the substance is in a higher concentration

-against concentration gradient

-need ATP

-need pumps

active transport pumps

1. Proton pumps, responsible for moving hydrogen ions into the lumen of the stomach.

2. Calcium pumps, responsible for normal function of neurons and muscle cells.

3. Sodium-potassium pumps, found in a wide variety of cells and integral to normal cellular metabolism

Endocytosis and exocytosis

macromolecules like polypeptides and polysaccharides are too large to be moved so they must be transported by either ______ and _____

-require the formation of a vesicle made of plasma membrane for transporting

phagocytosis

solid substance into cell; a form of endocytosis

-ingestion of yeast by a para­mecium and the engulfing of foreign substances by macrophages, a type of white blood cell that protects us from pathogens.

pinocytosis

Relatively large volumes of fluid, with their solutes, can be taken up by a cell through a form of endocytosis

exocytosis

a vesicle of phospholipid bilayer encapsulates the macromolecules inside the cell and merges with the cell membrane to release contents

Endocytosis

A vesicle of phospholipid bilayer is formed by the pinching
in of the cell membrane as something enters the cell