Download 3 - Membranes and Exchange - RHS-APES

Cell Membranes and Exchange of Materials across the
membrane!
Diffusion
Molecules move from an area of higher concentration to an
area of lower concentration until the concentration is the
same throughout. In (a), a crystal of potassium permanganate
(KMnO4) was dropped into a glass of water. The molecules
diffuse through the water (b) until they are evenly distributed
throughout (c).
A Semipermeable Membrane
• Molecules that move in and out of a cell
freely:
– WATER, OXYGEN, AND CARBON
DIOXIDE, AMINO ACIDS
– Why?
• They are small molecules
• Large molecules like PROTEINS AND
CARBOHYDRATES CANNOT move across
the membrane freely
• The Cell Membrane is
SEMIPERMEABLE (SELECTIVELY
PERMEABLE)
– ONLY ALLOWS CERTAIN MOLECULES
TO PASS THROUGH
Osmosis
• The diffusion of water
• Passive Transport
• Water diffuses from an area of high water
concentration to an area of low water concentration
Cells respond to their environment!
What process occurred that caused these red blood cells to
change shape?
How Cells Exchange Materials
3.3 Diffusion and Osmosis
Initially the cells are in a
solution with the same
concentration of dissolved
material as is found inside the
cells. This is called an isosmotic
solution. The animal cell can
survive only fairly small
variations from this
concentration.
Elodea
Red Onion
Paramecia
use a contractile vacuole to rid of excess water
Exocytosis
Endocytosis
A type of active transport
Examples of endocytosis
Phagocytosis – brings in “food”
Pinocytosis – cell brings in Water
CFTR Protein and Cystic Fibrosis
Exchange in Multicellular Organisms
Gas Exchange on LAND and water
Gas Exchange in Water
Water has oxygen in it, but
not in high concentrations
like in air
Organisms in water have
adaptations to removing
limited oxygen in water
Type of adapations?
Large surface area!
Gas Exchange in Water
Gas Exchange on Land
Gas Exchange in Humans
Oxygen is obtained from inhaled air. The air passes down the
trachea (windpipe) and enters the bronchi at the entrance to
the lungs. Each bronchus divides into smaller tubes called
bronchioles. At the end of the each bronchiole branch are
sets of air sacs. These air sacs are called alveoli.
This scanning electron micrographs shows the
organization of the pulmonary acinus. This micrograph
is of a cast of two terminal bronchioles, the short
respiratory, or transitional, bronchioles and all of the
alveolar air spaces supplied by those bronchioles.
Website link
An average adult has about 600 million alveoli,
giving a total surface area of about 100m². The walls
of the alveoli are composed of a single layer of flattened
epithelial cells, as are the walls of the capillaries, so gases
need to diffuse through just two thin cells. Water diffuses
from the alveoli cells into the alveoli so that they are
constantly moist. Oxygen dissolves in this water before
diffusing through the cells into the blood, where it is
taken up by haemoglobin in the red blood cells.
Waste removal in organisms
• What are the 3 types of nitrogen waste?
– Ammonia
– Urea
– Uric Acid
– What kind of organisms excrete each? Where
would these organisms each live?
Waste Removal in Humans – The
Excretory System
The kidney is made of nephrons
Each kidney is bean-shaped and
about the size of an adult's fist.
The kidneys are located below the
ribs and toward the back.
They contain nearly 40 miles of
tubes, most of them tiny, that
process some 100 gallons of
blood each day.
The kidneys filter and clean the
blood, and they produce urine
from excess water and dissolved
solids.
What Causes Kidney Stones?
Kidney stones are hardened crystal clumps that can develop
in the urinary system. They usually form because there is a
breakdown in the balance of liquids and dissolved solids in
the urine. The kidneys must keep the right amount of water
in the body while they remove materials that the body
cannot use. If this balance is disturbed, the urine can
become overloaded with substances (usually small crystals)
that won't dissolve in water. Crystals begin to stick together
and slowly add layer upon layer to form a stone. A kidney
stone may grow for months or even years before it causes a
problem.
Kidney stones don't all look the same. The color depends on
what chemicals are in it. Most are yellow or brown, but they
can be tan, gold, or black. Stones can be round, jagged, or
even have branches. They vary in size from specks to
pebbles to stones as big as golf balls.
Who Gets Kidney Stones?
Anyone can get kidney stones, but some people are more likely to
develop stones than others. Typically, a person with a kidney stone is a
man 20 to 60 years old. Although four out of five kidney stone sufferers
are men, women also get kidney stones. Often, there is a family history
of kidney stones. Chronic dehydration (lack of body water) can lead to
kidney stones. Very hot weather, heavy sweating, or too little fluid intake
contribute to the formation of kidney stones. People who work outdoors
in hot weather and who do not drink enough fluids may increase their
risk of getting stones.
Website on kidney stones
Feedback Regulation
(pump ions out using ATP energy; inside becomes negatively charged)