The Membrane Plasma membranes are amphiphilic which means they have hydrophilic and hydrophobic regions. Hydrophilic – attracted to water Hydrophobic – “scared” of water Cell membranes are selectively or semi permeable which means that some materials move through the membrane and hinders the movement of others. The cell membrane is primarily composed of a mix of proteins & lipids Lipids help to give membranes their flexibility, proteins monitor and maintain the cell's chemical climate and assist in the transfer of molecules across the membrane.

The Membrane Lipids Phospholipids: form a lipid bilayer in which their hydrophilic head areas arrange to face the cytosol and the extracellular fluid, while their hydrophobic tail areas face away from the cytosol and extracellular fluid.

The Membrane Lipids Cholesterol molecules are selectively dispersed between membrane phospholipids. This keeps the cell membranes from becoming stiff by preventing phospholipids from being too closely packed together. Glycolipids are located on cell membrane surfaces and have a carbohydrate sugar chain attached to them. They help the cell to recognize other cells of the body.

The Membrane Proteins Peripheral Proteins help cells communicate with their external environment Channel or Transport proteins transport molecules across cell membranes through facilitated diffusion Integral Proteins are embedded in the cell membrane and help in cell to cell communications and molecule transport across the membrane.

What will move? Fat-soluble material with a low molecular weight can easily slip through the hydrophobic lipid core of the membrane. Fat soluble vitamins readily pass through the plasma membranes in the digestive tract and other tissues. Fat-soluble drugs and hormones also gain easy entry into cells and are readily transported into the body's tissues and organs. Molecules of oxygen and carbon dioxide have no charge and so pass through membranes by simple diffusion.

What will move? Small ions could easily slip through the spaces in the membrane BUT their charge prevents them from doing so. Ions such as sodium, potassium, calcium, and chloride are PUMPED against the concentration gradient into a cell by active transport Simple sugars (glucose) and amino acids also need help with transport across plasma membranes, achieved by various membrane proteins (channels).

Transportation Mechanisms

What are the jobs cells need to do? Get food Convert energy Remove wastes Reproduce Grow and repair Transport substances

How does a cell do its jobs? The Cell membrane has two main functions: 1) Forms a boundary between the cell’s internal and external environment (like your skin) 2) Controls the movement of substances into and out of the cell. **It is Selectively Permeable (it only lets some things through)

How Cells Move Molecules 1) Passive Transport a) Diffusion: small molecules like water, oxygen, and carbon dioxide pass through the cell membrane easily The membrane is permeable (are allowed through) to these molecules Molecules move down concentration gradient Can be called SIMPLE DIFFUSION in which molecules move down the [ ] gradient Or FACILITATED DIFFUSION, which use a channel or transport protein to move molecules ****All types of Diffusion: Does not require energy*****

How Cells Move Molecules Concentration Gradient: Molecules will move from areas of high concentration to low concentration Example: People at party will try to move out of the crowded room at a party because it's more comfortable. Molecules do the same thing.

How Cells Move Molecules Osmosis is the diffusion of Water Movement of water is from an area of high water concentration to an area of low water concentration

How Cells Move Molecules Solute: particles which are dissolved in water Ex: Salt or sugar Solvent: the liquid that the particles are dissolved in

TYPES OF SOLUTIONS Hypertonic - Higher solute concentration outside of the cell than inside the cell More water inside than out initially Water diffuses out by osmosis

TYPES OF SOLUTIONS Hypotonic - Higher solute concentration inside the cell than outside the cell  Less water inside than out initially  Water diffuses in by osmosis

TYPES OF SOLUTIONS Isotonic - Equal solute concentrations inside and out water doesn't move

TYPES OF SOLUTIONS Human cells are very sensitive to changes in concentration of the blood

How Cells Move Molecules 2) Active Transport: Moves materials across the cell membrane against a concentration gradient (low to high conc.) Requires the use of energy Allows cells to collect certain substances in concentrations hundreds of times higher than those outside the cell

How Cells Move Molecules 3) Endocytosis & Exocytosis:  Cells use a process of taking materials into cell (endocytosis) & removing materials from cell (exocytosis)

Phagocytosis aka. “Cell Eating” The movement of solid particles through the cell membrane as it pinches off to form a Transport vessicle.

Pinocytosis aka. “Cell Drinking” The movement of dissolved particles through the cell membrane as it pinches off to form a Transport Vessicle.

Receptor Mediated Endocytosis The movement of dissolved particles through the cell membrane ONLY if they find a corresponding Receptor.

Energy & The Cell

Cells and Energy We’ve learned in previous lessons that cells use energy- active transport and endocytosis and exocytosis. Where does the energy come from?

Chemical Energy and ATP Energy comes in many forms, including light, heat, and electricity. Energy can be stored in chemical compounds, too. For example: when a candle burns, carbon and hydrogen in the wax combine with oxygen from the air to produce water and carbon dioxide. This process releases energy in the form of light and heat.

Where does energy for a cell come from? Cellular Respiration! This process where glucose molecules are oxidized. During this process energy that was stored in the glucose bonds are released. Glucose + Oxygen  Carbon dioxide + water + energy

Energy Living things store energy mainly in the form of chemical bonds. Within your cells, energy is constantly moved around from one large molecule to another. How does the energy get converted from a food molecule to a muscle molecule? The answer is adenosine triphosphate (ATP)

In the mitochondria… The energy molecule cells use is called adenosine triphosphate (ATP) -The phosphate groups are all negatively charged (repel each other) It takes a LOT of energy to force the phosphate groups together Bonds are similar to springs- they store energy. When spring is released, energy is released. When the bonds are broken, energy is released.

ATP -The energy of ATP can be used in a cell when the phosphate groups are broken off -When one phosphate molecule breaks off, ADP is formed and energy is released  -another phosphate can be bonded on to remake ATP once again (Renewable energy)

ATP Being able to form and breakdown ATP helps the cell to store store ALL the ATP (energy) it needs it makes the energy as it needs it ATP is a small molecule that can attach to a cell while the energy is needed when the phosphate group has been broken off, the ADP molecule is released and a new phosphate can attach.

ATP vs ADP

Animation or video https://www.youtube.com/watch?v=00jbG_cfGuQ (until 4:10) http://www.biologyinmotion.com/atp/index.html