Chapter ThreeExchanging Materials with the Environment

What is this picture about?

What are two details observed in this picture?

What is one very important idea represented in this picture?

Exchanged MaterialsWhat is the role of the cell

membrane?

The cell membrane regulates the passage of materials into and out of the cell.

Single celled bacteria:Wall made of

carbohydrates and proteins.

A membrane made primarily of phospholipids.

Exchanged MaterialsMaterials needed for life must enter the cell

and certain materials must leave the cell … what are they?

Exchanged MaterialsWater

CO2 and O2

Sodium, Magnesium, Calcium, Hydrogen, Chloride, Potassium

Sugars, Amino Acids, Lipids

Ammonia

Membrane as a BarrierBased on the picture –

how is a cell membrane constructed?

The membrane consists of two thin layers of phospholipids.

Hydrophobic/ Hydrophilic?

Nonpolar tails repel charged particles but allow fat-soluble molecules to pass.

Membrane as a BarrierWhat might determine

if material can pass through the cell membrane?

Polarity, size, and electric charge.

Small gases (O2 and CO2) as well as small polar molecules (water and ethanol) pass freely.

Membrane as a BarrierHow do charged ions

and large polar molecules (glucose and a.a.’s) pass through the membrane?

Transport proteins embedded in the membrane help polar molecules such as sugars and aa’s.

Membrane as a BarrierThis diagram shows

selective permeability. What does it mean to be selectively permeable?

The cell membrane is selectively permeable.

The outside of the cell membrane is involved in communication.

Glycoproteins act as antennae.

What is this picture about?

What are two details observed in this picture?

What is one very important idea represented in this picture?

Diffusion and OsmosisExplain how the “concentration” or “density” of

the particles in the picture affects their movement.

The movement of molecules from high concentration to low concentration is diffusion.

Diffusion and OsmosisThe first picture in this

grouping has a high concentration gradient. Define concentration gradient.

A difference in concentration across a distance is a concentration gradient.

What happens at equilibrium?

Explain what is happening with the purple dye.

Diffusion and OsmosisHow is this picture an example of

concentration gradient and diffusion?

Diffusion and OsmosisHow is diffusion

responsible for keeping this plant looking healthy?

The diffusion of water down a concentration gradient is called osmosis.

Diffusion and OsmosisPROBLEM

With the cytoplasm and organelles, an animal cell is about 98% water. What would happen to …

an animal cell placed in distilled water (100% water)?

an animal cell placed in a high salt solution (90% water)?

Diffusion and OsmosisWhat might affect

the rate of diffusion?

Steeper concentration gradient.

Surface area.

Passive and Active TransportCells may need

concentrations inside that differ from simple diffusion.

How might this happen?

Passive transport involves diffusion without any input of energy.

Active transport uses energy to move substances against the concentration gradient.

Passive and Active TransportWhat if a substance is

too big to diffuse through the membrane?

Facilitated diffusion is a type of passive transport involving membrane proteins as channels.

Very large molecules move across the cell by way of endocytosis and exocytosis.

Gas Exchange in WaterWhat is cell

respiration, and what gases are exchanged?

Cell respiration releases energy for metabolism; O2 is used and CO2 is released.

Gas Exchange in WaterHow do O2 and CO2

move across the membrane?

O2 and CO2 must be dissolved in water for diffusion to take place.

Consistency of the membrane?

Gas Exchange in WaterWater environments

contain small amounts of dissolved oxygen.

Concentration gradient?

As a result … surface area for gas exchange?

Gas Exchange in WaterFish gills have a large

surface area made of many fine filaments.

Filaments are composed of capillary rich disks.

Water flows past, countercurrent to the blood flow – gases are exchanged efficiently.

Gas Exchange on LandDue to a moist gas

exchange surface, land based organisms risk dehydration.

How have organisms on land evolved to resolve this?

Gas Exchange on LandIn insects, gas

exchange occurs through branching air tubes called tracheae.

Air flows in and out of tracheae through openings called spiracles.

The spiracles can close to retain water.

Adaption to Life on LandYour nasal cavities

moisten, warm and filter the air you breathe – why is that necessary?

Air passes through the nose and mouth, past the pharynx and larynx, down the trachea and bronchus to the lungs.

Adaption to Life on LandThe lungs contain

millions of microscopic cavities for gas exchange called alveoli.

If gas exchange occurs at the alveoli – what must they be like?

Adaption to Life on LandThin

Large Surface Area (two large parking spaces)

Many Capillaries

O2 in and CO2 out

Cystic FibrosisCystic Fibrosis is a

genetic disorder resulting in coughs, lung infections and digestion difficulties.

The absence of one aa in cystic fibrosis transmembrane conductance protein (CFTR) prevents chloride regulation.

Cystic FibrosisThis affects

osmotic movement results in mucus build up.

What affects can mucus build up have on the lungs and digestive tract?

Adaption to Life on LandHow do plants prevent

water loss during gas exchange?

Plants have a waxy covering called the cuticle.

Gases move into and out of the leaf through openings called stomates – regulated by guard cells.

Adaption to Life on LandThe presence of

water regulates the guard cells.

How does water move up the stem of a plant?

Transpiration