Cell Physiology

What does the plasma membrane do?

surrounds cell to keep it intact

The plasma membrane is selectively what?

selectively permeable allowing certain ions and molecules in an out of the cell

Which molecules can pass through the membrane easily?

small lipid-soluble molecules such as O₂ and CO₂

What inorganic molecule can also pass through the membrane easily?

H₂O

Which molecules need help to get through the membrane?

ions and larger molecules

What is membrane transport?

movement of substances into and out of the cell

What are the 2 basic methods of transport?

passive and active transport

What is not required for passive transport?

energy

What must the cell provide in active transport?

metabolic energy in the form of ATP

What is a solution?

homogenous mixture of 2 or more components

What is a solvent?

dissolving medium; typically water in the body

What is a solute?

component in a smaller quantity within a solution

What is intracellular fluid?

cytosol (cytoplasm) and nucleoplasm

What is interstitial fluid?

fluid on the exterior of the cell

What does the membrane’s selective permeability influence?

movement both into and out of the cell

What is diffusion?

random movement of molecules from an area of higher concentration to an area of lower concentration

Even though molecules move in both directions, what does net movement through the membrane mean?

molecules will move from an area of higher concentration to an area of lower concentration until an equilibrium is reached

What is an example of net movement through the membrane?

O₂ is used to make ATP, so O₂ is used up and is let through from a higher concentration (exterior) to a lower concentration (interior)

What is osmosis?

diffusion of H₂O across the plasma membrane

What do solutes do in order to cross the plasma membrane?

dissolve in H₂O

What is tonicity?

the concentration of the solute in a solution stated as a percentage

What are the 3 different types of tonicity?

hypertonic, hypotonic, and isotonic

What does hypertonic mean?

solution with higher solute concentration; water moves out of the cell

What does hypotonic mean?

solution with lower solute concentration; water moves into the cell

What does isotonic mean?

solution with equal solute concentration; no net water movement

What is the relationship between the amount of solute and the amount of H₂O?

as the amount of solute increases, the amount of H₂O decreases

Why is it important for most body fluids to be isotonic (there’s the same concentration of non-diffusible solutes and H₂O on both sides of the membrane)?

the cell needs to maintain its usual size and shape

What is simple diffusion?

an unassisted process where solutes are lipid-soluble materials or small enough to pass through the membrane’s pores

What is facilitated diffusion?

where substances require a protein carrier for passive transport

What does facilitated diffusion transport?

lipid-insoluble and large substances

What are the 2 common forms of active transport?

active and vesicular transport

What is vesicular transport?

the movement of materials into or out of a cell using membrane-bound vesicles

What are the 2 types of vesicular transport?

exocytosis and endocytosis

What is exocytosis?

the process by which a cell releases substances by fusing vesicles with the cell membrane

What is endocytosis?

the process by which a cell takes in substances by forming vesicles from the cell membrane

What are the 2 types of endocytosis?

phagocytosis and pinocytosis

What is phagocytosis?

when a cell engulfs large particles or other cells

What is pinocytosis?

when a cell takes in liquids and dissolved substances