Biology-Chapter 5

Gated Ion Channels

May open or close in response to three kinds of stimuli: stretching of cell membrane, electrical signals, or chemicals in the cytosol or external environment, stimuli controls ability of specific ions to cross cell membrane

Phagocytosis

Movement of large particles or whole cells into the cell, many unicellular organisms feed by phagocytosis, certain cells in animals use phagocytosis to ingest bacteria and viruses that invade body

Active Transport

Movement of materials from an area of lower concentration to an area of higher concentration (up concentration gradient), requires a cell to expend energy. Examples: sodium-potassium pump, endocytosis, exocytosis

Exocytosis

Moving very large particles out of the cell, waters are moved out of cell in vesicles that fuse w/ the cell membrane

Facilitated Diffusion

Passage of materials aided by concentration gradient and transport proteins, high to low concentration

Carrier Protein

Serve in facilitated diffusion, transports molecules from high to low concentration from one side of cell membrane other side, no additional energy needed 1. Molecule binds to carrier protein 2. Carrier protein changes shape-altered shape may shield molecule from hydrophobic interior of lipid bilayer 3. Once shielded, molecule can be transported thru cell membrane 4. Molecule released from carrier protein on other side of membrane 5. Carrier protein returns to original shape

Difference Between Simple Diffusion, Osmosis, and Facilitated Diffusion

Simple diffusion requires no energy to move things across the cell membrane. Example: dye dropped into water and evenly distributing amongst the contents. Osmosis refers to the diffusion of WATER across the cell membrane. Example: putting salt in a cup of water causing it to have less water than before. Facilitated diffusion is the passage of materials aided by concentration gradient and transport proteins. Example: glucose of amino acids moving from blood into a cell. ALL PASSIVE TRASNPORT.

Multiple Ways in Which Ions Get Into Cell (what type of transport each of these methods are)

Sodium-Potassium Pump: -Only for Na+ and K+ Endocytosis: -Pinocytosis and phagocytosis Ion Channels: -Transport ions from high to low concentrations (passive transport) -Examples of ions they Transport: sodium (Na+), potassium (K+), calcium (Ca2+), and chloride (Cl-) -Ions aren't soluble in lipids so they can't diffuse across phospholipid bilateral w/out help from ion channels -Some are always open, some have gates that open to allow ions to pass or close to stop their passage -Gates may open or close in response to 3 types of stimuli: stretching of membrane, electrical signals, or chemicals in cytosol or external environment Carrier Proteins: -Serve in facilitated diffusion -Transport molecules form high to low concentration from one side of membrane to other -Doesn't require additional energy

Purpose of the Sodium-Potassium Pump, Which Way the Ions Transported

The sodium-potassium pump moves 3 sodium ions out for every 2 potassium ions moved into the cell. This creates a voltage across the cell called the membrane potential. Some animal cells must have a higher concentration of sodium outside the cell and a higher concentration of potassium ions inside the cell. This pump maintains these concentration differences. Ions are transported from low to high concentration.

Passive Transport

This process is when some substances cross the cell membrane without any input of energy by the cell. Examples: simple diffusion, facilitated diffusion, osmosis, ion channels

Pinocytosis

Transport of solutes or fluids into cells, "cell drinking"

Plasmolysis

When water leaves cells in a hypertonic environment and lose tug or pressure, reason plants wilt if they don't receive enough water

Crenate

When water moves out of cell and cell shrinks/shrivels in size

Hypertonic, Hypotonic, Isotonic (net movement of water and what happens to the cell)

-Hypertonic: net movement of water out of cell, shrink/shrivel -Hypotonic: net movement of water into the cell, burst/swell -Isotonic: NO net movement of water, remains same shape

3 Different Types of Active Transport

1. Endocytosis-involves moving large particles into the cell. Example: integral proteins 2. Exocytosis-moving very large particles out of the cell, wastes moved out of cell in vesicles that fuse with the cell membrane. Example: hormones 3. Sodium-potassium pump-moves 3 sodium ions out for every 2 potassium ions moved into the cell creating voltage across the cell called the membrane potential. Example: Na+/K+ (sodium/potassium)

Sodium-Potassium Pump

Active transport, moves 3 sodium ions out for every 2 potassium ions moved into the cell, creates voltage across cell called membrane potential

Cytolysis

Bursting/swelling of cells in hypotonic environment when water diffuses into cells

Hypertonic Solution

Concentration of solute molecules outside the cell is higher than concentration in cytosol, water diffuses OUT of the cell

Hypotonic Solution

Concentration of solute molecules outside the cell is lower than concentration in cytosol, water diffuses INTO the cell

Isotonic Solution

Concentrations of solutes outside and inside cell are equal, water diffuses IN AND OUT of the cell at equal rates, no net movement of water

Concentration Gradient

Difference in concentration of molecules across a distance Example of sugar cube added to beaker of water: 1. Sugar cube sinks to bottom of beaker 2. Sinking makes concentration of sugar molecules greater at bottom of beaker than at top 3. Sugar molecules begin to diffuse slowly thru water, moving towards low concentration due to dissolving of sugar

How Diffusion Happens (why/how the molecules spread out)

Diffusion happens when molecules move from an area of high concentration to an area of low concentration. Molecules move by their own natural kinetic energy. Molecules spread out because their goal is to reach equilibrium which is the balanced interal condition of cells. By spreading out, they are able to have an equal concentration on either side of the membrane. Molecules spread through their own kinetic energy.

Compare/Contrast Endocytosis and Exocytosis

Endocytosis: -Substances enter cell -Pinocytosis and phagocytosis are two different types -The cell engulfs large particles into VESICLES -External materials enclosed by a portion of the membrane which folds into itself to form a pouch then pouch pinches off from membrane and becomes vesicle Exocytosis: -Substances leave the cell -Only one type: exocytosis -Wastes moved out of cell in vesicles that fuse w/ the cell membrane -Substance released from the cell thru vesicle that transport substance to cell surface and fuses w/ the membrane to let substance out of cell -Vesicles release their contents into the cell's external environment Cells use exocytosis to release molecules that could potentially cause damage to the cell if released into cytosol Both: -Require cells to expend energy -Active transport -in endocytosis

Phospholipids

Heads are polar and contain phosphate group and glycerol, tails are non-polar, made up of 2 fatty acid chains

Equilibrium

In a sense of other influences, diffusion will eventually cause molecules to be in equilibrium0concentration of molecules will be the same throughout space