Chapter 3.3 Flashcards
What is Diffusion?
the tendency of atoms, molecules, and ions in a liquid or air to move from areas of higher concentrations to areas of lower concentrations
Concentration Gradient
A difference of concentration between two different areas
Diffusional Equilibrium
Random movements continue, but there is no further net movement, and the concentration of a substance remains uniform through the solution
Diffusion can only occur if
the cell membrane is permeable to that substance and a concentration gradient exists such that the substances is at a higher concentration on one side of the membrane or the other
What smalled solutes are not lipid-soluble?
Ions of sodium, potassium, and chloride, may diffuse through specific protein channels in the membrane
Facilitated Diffusion
This type of movement follows the concentration gradient, and because it requires membrane proteins it is considered to be “helped”
Facilitated diffusion can move
molecules only down a concentration gradient
What is Osmosis?
The movement of water across a selectively permeable membrane into a compartment containing solute that cannot cross that membrane.
One can think of impermeant solute as
solute that is “trapped” on one side of the membrane.
Osmotic Pressure
This ability of osmosis to generate enough pressure to lift a volume of water
Isotonic
Any solution that has the same osmotic pressure as body fluids
Hypertonic
Solutions that have a higher osmotic pressure than body fluids.
What happens if cells are put in a Hypertonic solution?
Water moves by osmosis out of the cell into the surrounding solution, and the cell shrinks
What happens if cells are put in a Hypotonic solution?
Has lower osmotic pressure than body fluids, gain water by osmosis and swell.
Filtration
Another process that foces molecules through membranes by exerting pressure.
What is Active Transport?
Movement against a concentration gradient. It requires energy, which comes from ATP molecules that split during the process of cellular metabolism.
What are “pumps”
Because these carrier transport substances from regions of lower concentration to regions of higher concentration
Endocytosis
conveys molecules or other particles too large to enter a cell by other means to the inside in a vesicle that forms from budding inward of a section of the cell membrane
Pinocytosis
Cells take in tiny droplets of liquid from their surroundings, as a small portion of cell membrane indents.
Phagocyotsis
Similar to pinocytosis, but the cell takes in solids rather than liquids.
Phagocytes
They can take in solid particles such as bacteria and cellular debris. When a particles outside the cell touches the cell membrane, a portion of the membrane projects outward and draws it inside the cell
What is a Phagosome
The part of the cell’s membrane surrounding the particle then detaches the cell’s surface, forming this vesicle
What is a Phagolysosome?
When a lysosome joins a phagosome, it forms this
What is Receptor-Mediated Endocytosis
Moves very specific types of particles into the cell. It uses protein molecules that extend though the cell membrane and are exposed on its outer surface.
What are ligands?
Molecules that bind to specific receptors
How do cholesterol molecules enter the cell?
Through receptor-mediated endocytosis.
Cholesterol molecules synthesized in liver cells are packaged into
large spheerical particles called low-density lipoproteins (LDL)
What is Exocytosis?
When the packaging of substances made in the cell into vesicles that fuse with the cell memrbane and are released outside the cell.
What is Transcytosis?
Combines endocytosis and exocytosis to selectively and rapidly transport a substsance or particles from one end of a cell to the other. Moves susbtances across barriers formed by tightly connected cells
What are exosomes?
These vesicles bud from one cell and then encounter, merge with, and enter other cells.
What do exosomes carry?
They carry lipids, proteins, and RNA. Remove debris, transport immune system molecules from cell to cell, and provide a vast communication network among cells
Diffusion Characteristics
Molecules move through the phospholipid bilayer from regions of higher concentration towards regiions of lower concentration
Diffusion source of energy
Molecular Motion
Diffusion Example
Exchange of oxygen and carbon dioxide in the lungs
Facilitated Diffusion Example
Ions move through channels, or molecules move by carrier proteins, across the membrane form a region of higher concentration toward one of lower concentration
Facilitated Diffusion Source of Energy
Molecular Motion
Facilitated Diffusion Examples
Movement of glucose through a cell membrane
Osmosis Characteristics
Water molecules mvoe through a selectively permeable membrane thoward the solution with more impermeant solute (greater osmotic pressure)
Osmosis SOurce of Energy
Molecular Motion
Osmosis Examples
Distilled water entering a cell
Filtration Characteristics
Smaller molecules are forced through porous membranes from regions of higher pressure to regions of lower pressure
Filtration Source of Energy
Hydrostatic Pressure
Filtration Examples
Molecules leaving blood capillaries
Active Transport Characteristics
Carrier molecules transport molecules or ions through membranes from regions of lower conentration toward regions of higher concentrations
Active Transport SOurce of Energy
ATP
Active Transport Examples
Movement of various iosn and amino acids through membranes
Pinocytosis Characteristics
Membrane engulfs droplets containing dissolved molecules from surroundings
Pinocytosis Source of Energy
ATP
Pinocyotsis Examples
Uptake of water and solutes by all body cells
Phagocytosis Charcteristics
Membrane engulfs solid particles from surroundings
Phagocytosis Source of Energy
ATP
Phagocytosis Examples
White blood cell engulfing bacterial cell
Receptor-Mediated Endocytosis Characteristics
Membrane engulfs selected molecules combined with receptor proteins
Receptor-Mediated Endocytosis Source of Energy
ATP
Receptor-Mediated Endocytosis Exxamples
Cell removing cholesterol-containing LDL particles from its surroundings
Exocytosis Characteristics
Vesicles fuse with membrane and release contents outside of cell
Exocytosis Source of Energy
ATP
Exocytosis Examples
Protein secretion, neurotransmitter release
Transcytosis Characteristics
Receptor-mediated endocytosis and exocytosis move particles through (into and out of) a cell
Transcytosis Source of Energy
ATP
Transcytosis Examples
HIV Crossing A Cell LAyer
Three Types of Endocytosis
Pinocytosis
Phagocytosis
Receptor-Mediated Endocytosis
