BIOLOGY CH8PPTOL 25PTS
CHAPTER 8 Cells &Their Environment
NAME_______________________
HOMEOSTASIS & the CELL MEMBRANE
HOMEOSTASIS is the maintenance of stable ____________________ conditions in a changing environment.
One way a cell maintains Homeostasis is by controlling the movement of substances across the cell membrane.
Q1 GIVE AN EXAMPLE OF AN IMPORTANT SUBSTANCE THAT IS MOVED IN OR OUT OF A CELL.
THE CELL MEMBRANE
Outer Limit Of Cell
Controls What Moves In And Out = SELECTIVELY ___________________
Phospholipid Bilayer
Water-soluble “Heads” Cell Surfaces
Water-insoluble “Tails” C ell Interior
Permeable To Non-Polar Substances
Q2 DIAGRAM AND LABEL A SECTION OF PHOSPHOLIPID BILAYER
CELL MEMBRANE
Made of phospholipids made of a phosphate “head” and two fatty acid “tails.”
LIPID BILAYER-The phospholipids form a barrier through which only small, nonpolar substances can pass.
PHOSPHATE head is POLAR and is attracted to water -HYDROPHILIC
FATTY ACID tails are NONPOLAR and are repelled by water-____________________________________
Because there is water inside and outside the cell, the phospholipids form a double layer called the LIPID BILAYER.
Only certain substances can pass through the lipid bilayer it is said to be SELECTIVELY PERMEABLE
IONS and most polar molecules are repelled by the nonpolar interior of the lipid bilayer.
Q3 GIVE AN EXAMPLE OF HOW THE CELL MEMBRANE IS SELECTIVELY PERMEABLE
MEMBRANE PROTEINS
Proteins in the cell membrane include cell-surface markers, receptor proteins, enzymes, and transport proteins.
Various proteins can be found in the cell membrane.
Some proteins face inside the cell, and some face outside.
Other proteins may stretch across the lipid bilayer and face both inside and outside.
MEMBRANE PROTEINS
CELL-SURFACE MARKERS act like a name tag
Carbohydrates attached to the surface by proteins called ___________________________________.
RECEPTOR PROTEINS enable a cell to sense its surroundings by binding to certain substances outside the cell.
ENZYMES in the cell membrane help with important biochemical reactions inside the cell.
TRANSPORT PROTEINS bind and move select molecules
Q4 WHICH TYPE OF MEMBRANE PROTEIN IS AN ATPase?
SECTION 2: CELL TRANSPORT
CELL TRANSPORT may divided into 2 major types of process
Passive Transport- substances move down or ____________________the concentration gradient
Active Transport- substances move up or against their concentration gradient and use cell energy
Q5 HOW DO I KNOW IF A PROCESS IS ACTIVE TRANSPORT?
PASSIVE TRANSPORT:
Substances Cross The Cell Membrane DOWN Their Concentration Gradient.
EQUILIBRIUM In solution, randomly moving molecules fill up a space, as the space is filled evenly equilibrium is reached.
CONCENTRATION The amount of a particular substance in a given _________________________________
When one area has a higher concentration than another area does, a concentration gradient exists.
DIFFUSION The movement of substances down a concentration gradient is called diffusion.
Q6 GIVE AN EXAMPLE OF DIFFUSION IN YOUR HOUSE
CELL MEMBRANE
Separates the cytoplasm from the fluid outside the cell.
Some substances enter and leave the cell by diffusing across the cell membrane.
The direction of movement depends on the concentration gradient and does _________ require energy.
Some substances diffuse through the lipid bilayer.
Other substances diffuse through transport proteins.
Q7 WHY DO SUBSTANCES DIFFUSE?
SIMPLE DIFFUSION
SMALL, NONPOLAR molecules can pass directly through the Lipid Bilayer.
Oxygen moves DOWN its concentration gradient into the cell.
Carbon dioxide diffuses _____________________ of the cell.
Natural Steroid hormones, which are nonpolar can also diffuse across the lipid bilayer.
Q8 GIVE 1 EXAMPLE OF A SUBSTANCE THAT WOULD DIFFUSE INTO YOUR CELLS IF YOU TOUCHED IT
SIMPLE DIFFUSION
Movement Of Substances From Regions Of Higher Concentration To Regions Of Lower Concentration
Oxygen, Carbon Dioxide And Lipid-soluble Substances
FACILITATED DIFFUSION.
Transport Proteins Help Substances Diffuse Through The Cell Membrane
Two types of transport proteins are CHANNEL proteins &CARRIER proteins. CHANNEL PROTEINS ions and polar molecules important for cell function diffuse through channel proteins.
sometimes called _________________________________, serve as tunnels through the lipid bilayer.
Each channel allows the diffusion of specific substances that have the right size and charge.
CARRIER PROTEINS transport substances that fit within their binding site.
A carrier protein binds to a specific substance on one side of the cell membrane.
This binding causes the protein to change shape.
As the protein’s shape changes, the substance is moved across the membrane and is released on the other side.
Q9 GIVE A SPECIFIC EXAMPLE FOR EACH TYPE OF FACILITATED DIFFUSION
OSMOSIS- Osmosis allows cells to maintain water balance as their environment changes.
Water can diffuse across a selectively permeable membrane in a process called osmosis.
Osmosis in cells is a form of facilitated ______________________________________.
Polar water molecules do not diffuse directly through the bilayer.
The cell membrane contains channel proteins that only water molecules can pass through.
If a concentration gradient exists across a membrane for solutes, a gradient also exists for water.
Osmosis occurs as free water molecules move down their concentration gradient
Q10 CAN WATER DIFFUSE DIRECLTY THROUGH THE FATTY ACID TAILS OF THE BILAYER?
OSMOSIS = Movement of WATER through a selectively permeable membrane from regions of HIGHER concentration to LOW
Water moves toward a higher concentration of solutes
OSMOSIS & TONICITY
The direction of water movement in a cell depends on the concentration of the cell’s environment.
If the solution is HYPERTONIC, or has a higher solute concentration than the cytoplasm does, water moves out of the cell.
The cell loses water and shrinks and undergoes __________________________________________
If the solution is ISOTONIC, or has the same solute concentration that the cytoplasm does, water diffuses into and out of the cell at
equal rates. The cell stays the same size.
If the solution is HYPOTONIC, or has a lower solute concentration than the cytoplasm does, water moves into the cell.
The cell gains water and expands in size. If left unchecked, the swelling caused by a hypotonic solution could cause a cell to burst or undergo PLASMOLYSIS
The rigid cell walls of plants and fungi prevent the cells of these organisms from expanding too much. In fact, many plants are
healthiest in a hypotonic environment.
Q11 BASED ON WHAT YOU KNOW WHAT WOULD HAPPEN TO YOU IF YOU WERE LEFT IN THE OCEAN FOR 3
DAYS? EXPLAIN YOUR ANSWER
OSMOSIS
Osmotic pressure: Ability of osmosis to generate enough pressure to move a volume of water
Osmotic pressure increases as the concentration of non-permeable solutes increases
Hypertonic – higher osmotic pressure
Hypotonic – lower osmotic pressure
Isotonic – same osmotic pressure
ACTIVE TRANSPORT
How do substances move against their concentration gradients?
Active transport requires energy to move substances against their concentration gradients.
In order to move substances against their concentration gradients, cells must use energy.
Most often, the energy needed for active transport is supplied directly or indirectly by ATP.
Q12 HOW DO I KNOW IF A PROCESS IS AN EXAMPLE OF ACTIVE TRANSPORT??
ACTIVE TRANSPORT
CARRIER MOLECULES transport substances across a membrane from regions of LOWER concentration to regions of HIGHER
concentration using ATP EXAMPLES Sugars, amino acids, sodium ions, potassium ions, etc.
ACTIVE TRANSPORT: The Na+/K+ ATPase
Many active transport processes use carrier proteins to move substances.
In active transport, the carrier proteins do require energy to “pump” substances AGAINST their concentration gradient.
The Na+/K+ ATPase or Sodium-Potassium Pump is a carrier __________________ that
actively transports three sodium ions out of the cell and two potassium ions into the cell.
This pump is one of the most important carrier proteins in animal cells. It prevents
sodium ions from building up in the cell, resulting in osmosis into the cell.
The concentration gradients of sodium ions and potassium ions also help transport other
substances, such as glucose, across the cell membrane.
Q13 IS THE NaKATPase A CARRIER MOLECULE? EXPLAIN
VESICLES-Mass Transport
Many substances, such as proteins and polysaccharides, are too ________________ to be transported by carrier proteins.
Instead, they cross the cell membrane in vesicles, which are membrane-bound sacs.
The vesicle membrane is a lipid bilayer, like the cell membrane.
Therefore, vesicles can bud off from the membrane, fuse with it, or fuse with other vesicles.
ACTIVE TRANSPORT: VESICLES-Mass Transport
ENDOCYTOSIS. The movement of a large substance into a cell by means of a vesicle
EXOCYTOSIS The movement of material out of a cell by means of a _______________________________
During exocytosis, vesicles inside the cell fuse with the cell membrane. From the cell membrane, the contents of the vesicle are
released to the outside of the cell. ENDOCYTOSIS = Cell engulfs a substance by forming a vesicle around the substance
Three types
Pinocytosis:substance is mostly water
Phagocytosis: substance is a ___________________________
Receptor-mediated endocytosis: requires the substance to bind to a membrane-bound receptor
Q14 WHICH USES MORE ENERGY THE NaKATPase OR ENDOCYTOSIS
EXOCYTOSIS- Reverse of endocytosis
Substances in a vesicle fuse with cell membrane
Contents released outside the cell
Release of neurotransmitters from __________________________ cells
Q15 DIAGRAM THE RELEASE OF NEUROTRANSMITTERS AT THE NEUROMUSCULAR JUNCTION
WHAT ARE NEUROTRANSMITTERS? GIVE AN EXAMPLE WITH FUNCTION
SECTION 3: Cell Communication
SENDING SIGNALS
Cells communicate by sending chemical signals that carry information to other cells.
Cells use various methods of communication.
A signaling cell produces a SIGNAL, often a molecule, that is detected by the _______________________ cell.
Typically, target cells have specific proteins that recognize and respond to the signal.
Neighboring cells can communicate through direct contact between their membranes.
Short-distance signals may act locally, a few cells away from the originating cell.
Long-distance signals are carried by hormones and nerve cells.
Q16 GIVE 2 EXAMPLES OF SIGNALING MOLECULES IN HUMANS
HORMONES = Signal molecules that are made in one part of the body.
Hormones are distributed widely in the bloodstream throughout the body, but they affect only specific ____________________.
Nerve cells also signal information to distant locations in the body, but their signals are not widely distributed.
While most signal molecules originate within the body, some signals come from outside.
For example, light has a great effect on the action of hormones in plants. The length of day determines when some plants flower.
Q17 DOES LIGHT AFFECT HUMANS? EXPLAIN
RECEIVING SIGNALS
A RECEPTOR PROTEIN binds only to signals that match the specific shape of its ____________________________ site.
A target cell is bombarded by hundreds of signals. But it recognizes and responds only to the few important for its function.
This response to some signals, but not to others, is made possible by receptor proteins, such as the ones in the cell’s membrane.
Q18 WHAT IS INSULIN? WHAT IS IT MADE OF AND WHAT DOES IT DO?
A RECEPTOR PROTEIN binds specific substances, such as SIGNAL MOLECULES.
The outer part of the receptor protein is folded into a unique shape, called the BINDING SITE.
Only the “right” ____________________________________ can fit into the receptor protein.
Once it binds the signal molecule, the receptor protein changes its shape in the membrane.
This change in shape relays information into the cytoplasm of the target cell.
Q19 DIAGRAM A HORMONE RECEPTOR BINDING COMPLEX
RESPONDING TO SIGNALS
A Cell May Respond To Signal By Changing Membrane Permeability, Activating Enzymes, Or Form A Second Messenger.
PERMEABILITY CHANGE Transport proteins may open or close in response to a signal.
ENZYME ACTIVATION Some receptor proteins are enzymes or they activate enzymes in the cell membrane.
SECOND MESSENGER Binding of a signal molecule outside the cell may cause a second messenger to form. The second
messenger acts as a signal molecule within the cell and causes changes in the cytoplasm and nucleus.
Q20 TESTOSTERONE IS AN EXAMPLE OF A SIGNAL WITH A SECOND MESSAGE. WHAT DOES IT TELL CELLS
TO DO?