Plasma Membrane and Transport of molecules

How do things get in and out of the cell?

I. The Plasma Membrane A. The fluid mosaic model describes the

structure of the plasma membrane. B. In this model the membrane is seen as a

bilayer of phospholipids.

PHOSPHOLIPID BILAYER = CELL MEMBRANE

Structure of the plasma membranePhospholipids with embedded proteins (proteins are for transporting molecules across membrane)

1. Phospholipids2. Proteins

2. Membrane lipids are phospholipids with polar, water-soluble heads and long, nonpolar, insoluble tails.

Polar

Non-Polar

2 Types of Cellular Transport

1. Passive Transport

2. Active Transport

Passive Transport

• Passive transport does not require energy input from a cell.

• Molecules can move across the cell membrane through passive transport.

• There are three types of passive transport. • diffusion• osmosis • Facilitated diffusion

Diffusion

• Diffusion is when molecules move down a concentration gradient.• Movement is from a

region of higher concentration to a region of lower concentration.

Examples:

• You can smell perfume because it diffuses into the air and makes its way into your nose.

• A teabag placed in a cup of hot water will diffuse into the water.

• Placing food coloring in a liquid will diffuse the color.

• Cigarette smoke diffuses into the air.• A few crystals of potassium permanganate in

water will diffuse and turn the water purple.• Stirring some sugar into tea will help it diffuse

quicker.• Leave a soda bottle open and the carbon dioxide

bubble will diffuse and leave it flat.

Osmosis

• Osmosis is the diffusion of water molecules across a semipermeable membrane.

• Water is moving from an area of higher concentration to an area of lower concentraion

• Osmosis animation

3rd Type of Passive Transport

Facilitated Diffusion = Facilitated diffusion- transport proteins embedded in the plasma membrane transport ions and molecules (that can’t get thru the membrane on their own) into and out of the cell as needed.

PASSIVE = NO ENERGY REQUIRED

Uses CHANNEL PROTEINS

Figure 8.13  One model for facilitated diffusion

Examples of Facilitated Diffusion

• Sodium and potassium ions

• Glucose moving into the bloodstream

Simple vs Facilitated Diffusion• BOTH with concentration gradient• BOTH passive

• FACILITATED = Channel proteins are used

2nd TYPE OF TRANSPORTActive transport- diffusion goes against the

concentration gradient meaning movement from an area of low concentration to an area of high concentration.

ENERGY REQUIRED! (ATP)GOES AGAINST CONCENTRATION

GRADIENT

TRANSPORT PROTEINS REQUIRED

Active Transport• Passive transport requires no energy

from the cell. • Active transport is powered by chemical

energy (ATP). • Active transport occurs through

transport protein pumps. • Cells use active transport to maintain

homeostasis.

• 2 Types of Active Transport• Protein pumps• Bulk Transport

Protein Pumps

• Protein pumps:

Using proteins to move small molecules from an area of low concentration to an area of high concentration through a membrane.(goes against the concentration gradient) Requires Energy

From low to high

Bulk Transport

• Bulk Transport: Moving large molecules by the process of vessicles. They are too large to pass through the membrane.

• 2 Types:– ENDOCYTOSIS (moving in)– EXOCYTOSIS ( moving out-exit)

Transport of large particles

2 Type of ACTIVE TRANSPORT: endo- and exocytosis

Endocytosis- a cell surrounds material and takes it in from its environment by enclosing it in a newly formed vacuole.

Exocytosis- vacuole containing what the cell needs to dump, merges with the plasma membrane releasing the material outside the cell.

Figure 8.18  The three types of endocytosis in animal cells

Figure 8.15  Review: passive and active transport compared

V. Diseases Associated with Difficulties in Transport across

membranes.

Diseases resulting from lack of functional channels/pumps

• Motor neuron problems -Na+ channel• Cystic fibrosis - Cl- channel• Bipolar disorder -Na+, K+, ATPase• Heart problems -Na+, K+, ATPase, Na+ channels• Resistance to chemotherapy - peptide transporter, p-

Glycoprotein, (Multi-Drug Resistance)• Color Blindness, H+ gradient as pump (rhodopsin)• Some Food Poisoning - Ca+ channel

What type of Transport?

• The small intestine is part of the digestive tract and is responsible for the digestion of food and absorption of nutrients. The lining of the small intestine is covered by epithelial cells with tiny hair-like follicles known as micro-villi. Lipids move directly into the epithelial cells lining the small intestine where they are then processed by organelles. They move from high conc to low.

• Diffusion

Which type of Transport?

• Other molecules such as amino acids are transferred into the epithelial cells with special transfer proteins within the membranes of epithelial cells. They move from high to low concentration

• Facilitated diffusion

Which type of Transport?

• When water moves from our intestinal cells to our intestines in cases such as diarrhea caused by cholera. Water is moving from an area of higher concentration to an area of lower concentration

• osmosis

What type of transport?

• What type of transport is responsible for food and oxygen molecules moving from the mother’s blood to the fetus’s blood supply through the placenta?

• Diffusion

What type of Transport?

• What type of transport is responsible when white blood cells engulf pathogens(which are too large to pass into the cell)?

• Endocytosis (phagocytosis)

Which Type of Transport?

• Paramecium and other single celled organisms have less water in their cells than the water that they are in. This causes the water to enter them so they need contractile vacuoles to keep from bursting. Which type of transport is responsible for this?

• Osmosis

What type of Transport?

• Nerve impulses require this type of transport. When a nerve impulse reaches the end of a cell, it causes the vesicles to fuse with the cell membrane and release the neurotransmitters outside of the cell.

• exocytosis

What type of transport?

• Your food is broken down into glucose, and it enters the cells lining the small intestine. It moves from an area of high concentration to an area of low concentration but it needs a transport protein.

• Facilitated diffusion

What type of transport?

• Minerals in the soil move into the roots against the concentration gradient. Sometimes there are more minerals inside the cell than outside. What type of transport is responsible?

• Active transport

Which way will the molecules move?

• IF the levels of Carbon dioxide are 60% outside the leaf and 45% in the leaf and Carbon dioxide moves by diffusion, which way will the molecules move?

• Into the leaf

Which type of transport?

• Active Transport