chapter 7 Flashcards
Why do cells need to move substances through their membrane?
To bring in nutrients, oxygen, and water and to release wastes, carbon dioxide, and excess water
What is a phospholipid?
Lipids that are the most abundant molecule type in the plasma membrane, consist of two fatty acid tails attached to a glycerol head that is bonded to a phosphate group.
What is a plasma membrane?
The membrane that surrounds the cell
What chemical properties of the phospholipid are important to a cell membrane (plasma membrane)?
They are amphipathic. This means that they have both hydrophilic and hydrophobic parts.
In what way is the phospholipid bilayer “fluid”?
It has the consistency of salad oil
What effect does cholesterol have on a membrane?
At warm temperatures, cholesterol restrains movement of phospholipids. At cool temperatures, it maintains fluidity by preventing tight packing
What is osmosis?
the diffusion of water across a selectively permeable membrane
How is osmosis different from diffusion?
Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration until the solute concentration is equal on both sides.
How is osmosis similar to diffusion
Both are passive transport
Diffusion
The tendency for molecules to spread out evenly into the available space; Substances diffuse down their concentration gradient, the region along which the density of a chemical substance increases or decreases
Osmosis
the diffusion of water across a selectively permeable membrane; Water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration until the solute concentration is equal on both sides
concentration gradient
the region along which the density of a chemical substance increases or decreases
Equilibrium
have approximately equal amounts of solute on either side of a membrane
How an Isotonic solution affects an animal and plant cell
animal cell size stays the same (ideal condition for animal cell), plant cell becomes flaccid causing the plant to wilt;
How a hypotonic solution affects an animal and plant cell
animal cell increases in size and may lyse, plant cell becomes turgid and makes the plant rigid by putting pressure against plant cell wall (ideal condition for plant cell)
How a hypertonic solution affects an animal and plant cell
would pull water out of both plant and animal cells causing animal cells to shrivel and plant cells to plasmolyze, both types of cells would die
facilitated diffusion
transport proteins speed the passive movement across the plasma membrane by diffusion
active transport
transport that moves solutes against their concentration gradient; uses carrier transport proteins and requires energy, usually in the form of ATP
passive transport
occurs through diffusion, doesn’t require energy to move molecules down the concentration gradient; includes simple diffusion, osmosis, and facilitated diffusion
Function of membrane protein: Transport
move substances around the cell or into/out of the cell
Function of membrane protein: enzymatic activity
speed up reactions
Function of membrane protein: signal transduction
allow for cell to cell communication
Function of membrane protein: cell-cell recognition
allow neighboring or immune cells to recognize that the cell is part of the body
Function of membrane protein: intercellular joining
allow attachment between neighboring cells
Function of membrane protein: attachment to cytoskeleton and ECM
cross membrane proteins that hold ECM in place
How do channel proteins aid in facilitated diffusion
Channel proteins provide corridors that allow a specific molecule or ion to cross the membrane
How do carrier proteins aid in facilitated diffusion
Carrier proteins undergo a subtle change in shape that translocates the solute-binding site across the membrane
Why is active transport needed?
Because the ions are being moved against their concentration gradient from areas of low concentration to areas of high concentration
Mechanisms that permit bulk transport across the cell membrane.
Exocytosis and endocytosis
Exocytosis
transport vesicles migrate to the membrane, fuse with it, and release their contents; Many secretory cells use exocytosis to export their products
endocytosis
the cell takes in macromolecules by forming vesicles from the plasma membrane (reversal of exocytosis); Types of endocytosis: Phagocytosis and Pinocytosis
Phagocytosis
(“cellular eating”) cell engulfs a particle in a vacuole,
Pinocytosis
(“cellular drinking”) cell takes in extracellular fluid
