BIO 181-Chapter 5: Structure and Function of Plasma Membranes

What are “integral proteins”?

Proteins that penetrate into or through the hydrophobic interior of the plasma membrane

What are “peripheral proteins”?

Proteins that are loosely attached to the surface of the plasma membrane

What is the role of carbohydrates on the plasma membrane?

They help cells recognize one another and can vary among species, individuals, and cell types

What does “selectively permeable” mean?

The membrane allows some substances to cross more easily than others

What is “passive transport”?

The movement of substances across a membrane without the cell using energy

Why is diffusion considered passive transport?

Because the cell does not expend energy to make it happen

What types of molecules cross the lipid bilayer easily?

Hydrophobic, nonpolar molecules (such as hydrocarbons)

What types of molecules do not cross the lipid bilayers easily?

Polar molecules (such as sugars)

What is “diffusion”?

The tendency of molecules to spread out evenly into available space

What is a “concentration gradient”?

A difference in the concentration of a substance between two regions

In which direction do substances diffuse?

From an area of higher concentration to an area of lower concentration

What does it mean to move down a concentration gradient?

To move from high concentration to low concentration

Does diffusion require cellular energy?

No

What is “facilitated diffusion”?

Passive transport in which membrane proteins help substances cross the plasma membrane

Does facilitated diffusion require energy?

No

What do “transport proteins” do in facilitated diffusion?

They help molecules move across the plasma membrane

What is a “carrier protein”?

A transport protein that binds a solute and changes shape to move it across the membrane

How do carrier proteins move substances across the membrane?

They bind the solute, change shape, and move the solute-binding site to the other side of the membrane

What is “osmosis”?

The diffusion of water across a selectively permeable membrane

In which direction does water move during osmosis?

From an area of lower solute concentration to an area of higher solute concentration until solute concentration is equal on both sides

Why does water move toward the side with more solute?

Because that side has a lower concentration of free water molecules

What happens to net water movement when equilibrium is reached?

There is no net movement of water, although water molecules may still more in both directions

What is “tonicity'“?

The ability of a surrounding solution to cause a cell to gain or lose water

What is an “isotonic solution”?

A solution with the same solute concentration as the inside of the cell

What happens to a cell in an “isotonic solution”?

There is no net movement of water, so the cell stays about the same size

What is a “hypertonic solution”?

A solution with a higher solute concentration than the inside of the cell

What happens to a cell in a "hypertonic solution”?

Water leaves the cell, causing the cell to shrink

What is a “hypotonic solution”?

A solution with a lower solute concentration than the insde of the cell

What happens to a cell in a “hypotonic solution”?

Water enters the cell, causing the cell to swell

What is the difference between “simple diffusion” and “facilitated diffusion”?

Simple diffusion occurs directly through the lipid bilayer, while facilitated diffusion requires transport proteins

How are diffusion, facilitated diffusion, and osmosis similar?

All are forms of passive transport and do not require cellular energy

What is the easiest way to remember hypertonic, hypotonic, and isotonic?

Hypertonic= water exits the cell, Hypotonic= water enters the cell, Isotonic= no net water movement

What is “osmoregulation”?

The control of solute concentrations and water balance in a living system

Why is osmoregulation important?

It helps cells maintain proper water balance and prevents them from swelling too much or shrinking

How do cell walls help with water balance?

They help prevent cells from busting when water enters

What is “active transport”?

The movement of substances across a membrane against their concentration gradient using energy

In which direction does active transport move solutes?

From lower concentration to higher concentration

Does active transport require energy?

Yes (usually in the form of ATP)

How is active transport different from passive transport?

Active transport requires energy and can move substances against their concentration gradient; passive transport does not require cellular energy

What is an “electrochemical gradient”?

A combines concentration and electrical gradient that influences the movement of ions across a membrane

Why does moving a substance against an electrochemical gradient require energy?

Because the substance is being moved in the opposite direction from the way it would naturally diffuse

What is endocytosis?

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

What happens to the plasma membrane during endocytosis?

The membrane folds inward, surrounds material, and pinches off to form a vesicle inside the cell

What is phagocytosis?

A type of endocytosis in which the cell engulfs large particles or solids

What does phagocytosis commonly mean?

“Cell-eating”

What is pinocytosis?

A type of endocytosis in which the cell takes in extracellular fluid and dissolved substances

What does pinocytosis commonly mean?

“Cell-drinking”

What is exocytosis?

A process in which vesicles fuse with the plasma membrane and release their contents outside the cell

What happens to transport vesicles during exocytosis?

They move to the plasma membrane, fuse with it, and release their contents

How are endocytosis and exocytosis opposite processes?

Endocytosis brings materials into the cell, while exocytosis moves materials out of the cell

Which transport process is used for very large particles that cannot pass through membrane proteins?

Endocytosis

Which transport process allows a cell to release large molecules or secretions?

Exocytosis

What is the cellular respiration formula?

C6H12O6+6O2 ——>6CO2+6H2O+energy (ATP)