Chapter 7

Endocytosis: Receptor-mediated endocytosis

- Occurs at receptor sites - Specific substances

Pinocytosis

Cell absorbs drops of extracellular matrix Drops contain dissolved molecules Forms small vesicles Non-specific

Phagocytosis

Common in Protists Cell engulfs large food particle Uses pseudopodia to create food vacuole This fuses with lysosome to digest food

Factors that affect rate of diffusion

Concentration gradient - Larger gradient -> faster diffusion Temperature - Increased temp -> faster diffusion Molecule size - Smaller molecules -> faster diffusion - Larger molecules -> slower diffusion Electrical gradient - Charge -> faster diffusion Pressure gradient - Increased pressure -> faster diffusion

(Sodium-Potassium Pump) 2 Potassium ions (K+) are pumped into cell

Potassium concentration is higher inside the cell - Pump moves potassium against it's concentration gradient Requires ATP

Endocytosis: Phagocytosis

Cell eating pseudopodia

When solution A has a higher concentration of water than solution B, solution A is _________________.

Hypotonic

(Endo)cytosis

Into cell

Two solutions in which the concentration of water is equal are called ___________

Isotonic

Hypotonic

More water Having a lower concentration of solute than another solution

Passive transport

Moves substances along concentration gradient - From high concentration to low concentration No energy required Two types: Simple diffusion and Facilitated diffusion

Simple diffusion

Small non-polar molecules, no transport proteins required

Tonicity

The measure and comparison of water potential of two solutions separated by a semi-permeable membrane - Depends on solute concentration & water concentration of one solution compared to solute concentration & water concentration of the second solution

Endocytosis: Pinocytosis

Vesicles pinch into cell

Cell and solution are Isotonic

Water concentration of the solution equals water concentration in the cell

as solute concentration decreases, water concentration ____________?

increases

What is a Solvent?

the dissolving agent - Water is the dissolving agent in aqueous solutions

Membrane Proteins

the mosaic part of cell membrane

Integral Proteins

Extend all the way through the plasma membrane Protrude on both the outer and inner surface ----------------------------------------------------------- Amphipathic - Has both hydrophilic and hydrophobic regions Hydrophobic region penetrates & binds to hydrophobic tails of plasma membrane phospholipid bilayer Hydrophilic regions protrude outside at least one side of the plasma membrane Some extend all the way through both sides of the plasma membrane - Transmembrane

Membrane Carbohydrates

Short, branched polymers - On extracellular side of membrane Can be attached to the phospholipids - Glycolipids Or, can be attached to proteins - Glycoproteins Function in Cell-Cell recognition - Blood type - Embryo development

(Sodium-Potassium Pump) 3 Sodium ions (Na+) are pumped out of cell

Sodium concentration is higher outside cell - Pump moves sodium against it's concentration gradient

Receptor-Mediated Endocytosis

Special type of pinocytosis Membrane proteins have receptor sites exposed to extracellular matrix Receptor sites bind to specific solutes

Osmosis

The diffusion of water Depends on solute concentration Depends on water concentration - Water moves from high concentration to low concentration

Exocytosis

Transporting out of the cell Vesicles fuse with cell membrane Waste products, hormones - Remember the Golgi apparatus Contents spill out into extracellular matrix Vesicle membrane becomes part of cell membrane

What is diffusion?

Type of passive transport Movement of particles from an area of high concentration to an area of lower concentration Spontaneous - Energy required?

Isotonic

- No net movement of water - Water diffuses in and out of cell, but in equilibrium

*Red blood cells are approximately ____ solute

1%

plant cells have a solute concentration of approximately___.

1%

A stalk of celery* is starting to wilt. To perk it up, would you place the celery in pure water, in a solution that is 1% sugar, or in a solution that is 10% sugar?

100% water or "pure" water

Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? - Any of the above would easily diffuse through the membrane. - A small nonpolar molecule - A large polar molecule - A large nonpolar molecule - Dissolved gases such as oxygen or carbon dioxide

A large polar molecule

Which of the following is a correct difference between active transport and facilitated diffusion? - Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. - Facilitated diffusion involves transport proteins, and active transport does not. - Active transport can move solutes in either direction across a membrane, but facilitated diffusion can only move in one direction. - Active transport requires energy from ATP, and facilitated diffusion does not. - Active transport involves transport proteins, and facilitated diffusion does not.

Active transport requires energy from ATP, and facilitated diffusion does not.

Transport Proteins

Assist molecules that cannot easily cross the plasma membrane They are specific to the molecules they transport

Why is energy required for active transport? - Because it moves solutes against their concentration gradient - To allow the movement of water from a hypotonic solution to a hypertonic solution - To allow the movement of solutes down their concentration gradient - To allow the movement of water from a hypotonic solution to a hypertonic solution - Because it helps maintain water balance in cells without walls

Because it moves solutes against their concentration gradient

Carrier proteins (transport proteins)

Bind to molecules to be transported then change shape to facilitate passage - Molecule avoids contact with hydrophobic tails of lipid bilayer

Which of the following molecules is most likely to passively diffuse across the plasma membrane? - DNA - Sodium ion - Glucose - Hemoglobin - Carbon dioxide

Carbon dioxide

What function do carbohydrates fulfill in the plasma membrane? - They facilitate enzymatic processes. - They contribute to its selective permeability. - They contribute to its "fluid" characteristic. - Cell-to-cell recognition - Transport of molecules across the membrane

Cell-to-cell recognition

Peripheral Proteins

Float on the outer or inner surface of the plasma membrane ----------------------------------------------------------- Are bound to one side of the plasma membrane only Have hydrophilic regions that interact with phospholipid heads of plasma membrane Are sometimes bound to integral proteins

Channel proteins (transport proteins)

Have hydrophilic channel Used by hydrophilic molecules and ions - Avoid contact with hydrophobic tails Ex: Aquaporins allow diffusion of water

From 19 above, solution B with the lower concentration of water is called __________________

Hypertonic

Which of the following statements about diffusion is true? - It is very rapid over long distances. - It always requires integral proteins of the cell membrane. - It occurs when molecules move from a region of lower concentration to a region of higher concentration. - It requires expenditure of energy by the cell. - It is a passive process.

It is a passive process.

Bulk Transport

Large molecules or many small molecules are packaged in vesicles and transported in bulk Exocytosis - Out of cell Endocytosis - Into cell

Hypertonic

Less water when comparing two solutions, the solution with the greater concentration of solutes

Active transport

Moves substances against concentration gradient - From low concentration to high concentration Requires energy - Requires energy in form of ATP Transport proteins required Protein is activated by ATP - Binding of ATP changes protein shape

The passive transport of water across a selectively permeable membrane is called ________.

Osmosis

(Exo)cytosis

Out of cell

Which of the following statements about passive transport is correct? - Passive transport permits the solute to move in either direction, but the net movement of the population of solute molecules occurs down the concentration gradient of the molecule. - Passive transport does not occur in the human body. - Passive transport operates independently of the concentrations of the moving solute. - Passive transport operates independently of diffusion. - In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane.

Passive transport permits the solute to move in either direction, but the net movement of the population of solute molecules occurs down the concentration gradient of the molecule.

Which of the following molecules are most abundant in the plasma membrane? - Cholesterol - Water - Phospholipids - Carbohydrates - Proteins

Phospholipids

Membrane Permeability

Plasma membranes regulate passage into and out of the cell. Nonpolar and uncharged molecules can cross easily Why? Ions (charged) and polar molecules need assistance Why? Small molecules can cross more easily than large

How does the "fluid mosaic model" describe the structure of the plasma membrane? - Only the proteins in the membrane contribute to its fluidity. - Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to its fluidity. - The fluid characteristic is due to the presence of carbohydrates, and the mosaic characteristic is due to the presence of phospholipids. - The plasma membrane is a rigid structure that exhibits little flexibility. - None of the listed responses is correct.

Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to its fluidity.

Facilitated diffusion

Small polar or ions, requires transport proteins

A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution? - The solution is hypotonic. - The cell is hypertonic. - The solution has the same solute concentration as the cell. - The solution is hypertonic. - None of the listed responses is correct.

The solution is hypertonic.

Which of the following is correct regarding peripheral proteins? - These proteins exhibit both hydrophilic and hydrophobic properties. - They have no specific function in the plasma membrane. - They exhibit only hydrophobic properties. - These proteins are found only on the surface of the plasma membrane. - They span the entire phospholipid bilayer.

These proteins are found only on the surface of the plasma membrane.

Which of the following is correct regarding integral proteins? - These proteins exhibit both hydrophilic and hydrophobic properties. - They have no specific function in the plasma membrane. - They exhibit only hydrophilic properties. - They exhibit only hydrophobic properties. - These proteins are found only on the surface of the plasma membrane.

These proteins exhibit both hydrophilic and hydrophobic properties.

Endocytosis

Three types: Phagocytosis - pseudopodia Pinocytosis - Vesicles pinch into cell Receptor-Mediated Endocytosis - Occurs at receptor sites - Specific substances

sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell

What is a Solution?

a liquid that is a completely homogeneous mixture of substances - Saltwater - Pedialyte

Active Transport is when a. A cell uses energy to move molecules or ions against a concentration gradient b. A cell does not use any energy to move molecules or ions across membrane c. A cell does not use transport proteins to move molecules

a. A cell uses energy to move molecules or ions against a concentration gradient

Functions of membrane proteins are: (mark all correct answers) a. Carry out chemical reactions b. Help cells communicate and recognize each other c. Transport materials across the membrane d. Synthesizing new polypeptides

a. Carry out chemical reactions b. Help cells communicate and recognize each other c. Transport materials across the membrane

The "fluid" part of cell membranes is made up of: a. Phospholipid bilayer b. Protein pumps c. Glycoproteins d. Carbohydrates e. Transport proteins

a. Phospholipid bilayer

What is one function of proteins in cell membranes? a. Transport into and out of the cell b. Photosynthesis c. Cellular respiration d. None of the above

a. Transport into and out of the cell

Exocytosis is when a. Vesicle move large/many particles out of the cell b. Vesicle move large/many particles into the cell

a. Vesicle move large/many particles out of the cell

Endocytosis is when a. Vesicles move large/many particles into the cell b. Vesicle s move large/many particles out of the cell

a. Vesicles move large/many particles into the cell

What is the function of the carbohydrates attached to proteins and lipids on the outside of the cell membrane? a. Pumps and channels b. Cell-to-cell recognition and communication c. Strength d. Break down organelles

b. Cell-to-cell recognition and communication

The net movement of a substance will follow a concentration gradient from an area of high concentration to an area of lower concentration. What is the name of this biological process? a. Refraction b. Diffusion c. Integration d. Sublimation

b. Diffusion

Passive transport a. Requires energy b. Diffusion across a membrane; no energy used by the cell c. Requires transport proteins d. Uses carrier proteins

b. Diffusion across a membrane; no energy used by the cell

Diffusion is a movement of particles from an area of low concentration to an area of high concentration, and requires energy a. True b. False

b. False

The component molecules of the cell membrane have two main parts, the head and the tails. These parts are either hydrophobic or hydrophilic. Which is which? a. Hydrophilic Tail and Hydrophobic Head b. Hydrophilic Head and Hydrophobic Tail c. Both Hydrophobic d. Both Hydrophilic

b. Hydrophilic Head and Hydrophobic Tail

Which of these statements best describes the function of the cell membrane? a. It allows substances to freely enter and exit the cell. b. It controls which substances enter and exit the cell. c. It prevents substances from entering the cell. d. It prevents substances from leaving the cell.

b. It controls which substances enter and exit the cell.

Facilitated diffusion a. Requires energy b. Movement of substances across a membrane with help from transport proteins, no energy required c. Movement of substances across a membrane without help from transport proteins

b. Movement of substances across a membrane with help from transport proteins, no energy required

If a red blood cell (solute concentration 1%) is placed in a solution that is 10% solute, which direction will water diffuse? a. Into the cell b. Out of the cell c. Into and out of the cell equally (equilibrium)

b. Out of the cell

Through many studies, including imagery of cells using an electron microscope, it has been determined that the cell membrane consists of two layers. This is known as the bilayer. What is this bilayer composed of? a. Chlorolipids b. Phospholipids c. Carbolipids d. Tellolipids

b. Phospholipids

The cell membrane is the outermost part of an animal cell, and, is located inside the cell wall in plant cells. What is another name for the cell membrane? a. Liquid Membrane b. Plasma Membrane c. Pastoral Membrane d. Conjoint Membrane

b. Plasma Membrane

A membrane is permeable to hydrogen (H2), but impermeable to sodium ions. Which molecule cannot move into the cell? a. Hydrogen b. Sodium ions c. Both hydrogen and sodium ions d. Neither

b. Sodium ions

In the question above, the red blood cell is _____________ compared to the solution. a. Isotonic b. Hypertonic c. Hypotonic

c. Hypotonic

Which of these is true of the cell membrane in both animal and plant cells? a. None of these b. It is fully permeable c. It is selectively permeable d. It is fully impermeable

c. It is selectively permeable

The tail of a phospholipid is... a. Made of carbohydrates b. Made of proteins c. Made of fatty acid chains d. Hydrophilic e. None of the above

c. Made of fatty acid chains

In the diagram below, what structure is labeled with the letter B? a. Carbohydrate b. Cholesterol c. Protein d. Lipid

c. Protein

A cell with water concentration 95% is placed in a beaker of solution with water concentration 98%. Which of the following is correct? a. The cell is hypertonic to the solution and water will diffuse out of the cell. b. The cell is hypotonic to the solution and water will diffuse into the cell. c. The cell is hypertonic to the solution and water will diffuse into the cell. d. The cell is hypotonic to the solution and water will diffuse out of the cell

c. The cell is hypertonic to the solution and water will diffuse into the cell.

In facilitated diffusion, __________ proteins provide openings in the plasma membrane for substances to flow through without changing structure, and __________ proteins allow passage of substances through the plasma membrane after undergoing a subtle change in shape. - receptor; channel - carrier; channel - peripheral; enzymatic - channel; carrier - active transport; signal transduction

channel; carrier

as solute concentration increases, , water concentration __________?

decreases

The head of a phospholipid is... a. Made of carbohydrates b. Made of proteins c. Made of nucleic acids d. Hydrophobic e. None of the above

e. None of the above

What are the two main types of membrane proteins?

integral and peripheral

A solution is both solvent (water) and ______.

solute

Solution = solvent + ______

solute

The plasma membrane exhibits selective permeability. This means that __________. - the plasma membrane allows any substance to flow through it easily - proteins in the membrane do not affect its permeability - the plasma membrane allows some substances to flow through it more easily than others - the structure of the plasma membrane does not affect its permeability - the plasma membrane does not allow any substance to flow through it

the plasma membrane allows some substances to flow through it more easily than others

What is a Solute?

the substance that is dissolved - NaCl in saltwater - Pedialyte crystals

The sodium-potassium pump __________. - transports sodium ions out of the cell - transports sodium ions out of the cell and transports potassium ions into the cell - does not require energy to function - transports potassium ions into the cell - transports glucose into the cell

transports sodium ions out of the cell and transports potassium ions into the cell