Chapter 7

The Cell and Its Environment

1. All Organisms are made from one or more cells.2. The cell is the basic unit of structure and function in organisms.3. All cells are produced from other cells.

The Cell Theory

Plasma MembraneWhat is it? Boundary that separates the cell from

its environment.

What is its purpose?Controls which particles enter and leave the cell

Amino AcidsGlucoseCarbon Dioxide

This is Called “Selective Permeability”The membrane only allows particles that are

used by the cell or expelled to cross the membrane

Lipid Bilayer

Composed of Phospholipids- two layers of phospholipids form the

plasma membrane

The plasma membrane is made up of a lipid bilayer.

What is a lipid bilayer?

One end is water soluble – Phosphate groupThe other end is nonsoluble. – Fatty acid end

Visual of the Lipid BilayerPhospholipid

Inside of the Lipid Bilayer are:- Proteins – allow for transport of molecules

- allow for chemical reactions- Carbohydrates – Recognition molecules- Cholesterol – helps separate the fatty acid ends

Make up of the Plasma MembraneWhat’s the basic structure of the Plasma Membrane?

Lipid Bilayer

Visual of the Plasma Membrane

Visual of the Plasma Membrane

Fluid Mosaic Model

What does it mean to be “fluid”? What is mean to be “Mosaic”?

The components of the membrane are constantly moving

Why doesn’t it break apart?

Phospholipids are:Hydrophilic – Polar ends – attracted to H20 (dissolves)Hydrophobic – nonpolar end – not attracted to H20

(does not dissolve)

Visual of the Fluid Mosaic Model

Membrane Function

Diffusion?

Random movement of particles from a greater

concentration to a region of lesser concentration

Until “dynamic equilibrium”

OsmosisWhat is it? The diffusion of water into and out of cells across a

selectively permeable membrane

Cells must maintain Osmotic Balance. Why?

More Osmosis

Even More

Osmosis

Fig. 7-13

(a) Animal cell

(b) Plant cell

H2O

Lysed

H2O

Turgid (normal)

Isotonic solution Hypotonic solution

H2O

H2O

H2O

H2O

Normal

Flaccid

H2O

H2O

Shriveled

Plasmolyzed

Hypertonic solution

Facilitated DiffusionThe transport of particles across the plasma membrane

with the use of transport proteins.

Channel Proteins (Pores)- Allow transport of ions- They are specific to the size and charge of the ions

Carrier Proteins – two types- change shape to allow certain molecules to cross the

plasma membrane2. Gates – one particle attaches to the carrier protein

changing its shape – allowing particles to freely pass across the membrane.

Visual of Facilitated Diffusion

More Facilitated Diffusion

Active Transport

Movement of particles from an area lesser concentration to an area of greater concentration

It costs the cell energy – that’s the difference between facilitated and active transport

The transport proteins for active transport are called “pumps”

Visual of Active Transport

Review Passive & Active Transport

Endocytosis and ExocytosisEndocytosis – the plasma membrane surrounds and takes in

substances from the environment

Exocytosis – removal of substances from the cell, opposite of Endocytosis

Endocytosis – PhagocytosisPhagocytosis – solid chunks of material are taken into the cell

Endocytosis – PinocytosisPinocytosis – liquid is taken into the cell

Endocytosis – Receptor-AidedProtein Receptors identify specific particles for endocytosis

Endocytosis

Review - In your lab groups answer the following questions.

Define part “A” and “B” of the Molecule Below.

Explain how each part of the molecule behaves in H20?

B

A

Review

Draw the arrangement of Molecules that make up the plasma membrane.

1. Explain the function of each molecule.2. What makes the plasma membrane permeable to Water?3. What does it mean to be selectively permeable?

Review

What process causes water to enter a single cell organism? What is this Process called?

What would happen to a single cell pond organism that was placed into pure water? Why?

What would happen to a single cell pond organism that was placed into salt water? Why?

ReviewDiagram and explain the similarities and differences of the following:

1. Diffusion, Osmosis and Facilitated Diffusion.2. Channel Proteins, Carrier Proteins and Gate Proteins.3. Phagocytosis, Pinocytosis and Receptor-aided endocytosis.

Answer to #2Channel Proteins (Pores)

- Allow transport of ions- They are specific to the size and charge of the ions

Carrier Proteins – two types1. change shape to allow certain molecules to cross the

plasma membrane2. Gates – one particle attaches to he carrier protein

changing its shape – allowing particles to freely pass across the membrane.

ReviewExplain the difference between Active and Passive Transport.