Biology Ch. 5

fluid mosaic

Fluid (molecules can drift in membrane) and mosaic (small pieces and different functions). Description of membranes.


Proteins that give the membrane a stronger framework. Attach to cytoskeleton on the inside and the extra cellular matrix (ECM) on the outside.

cell-cell recognition

What glycoproteins are involved in. Second function of plasma membrane. Outside surface of membrane has carbohydrates bonded to proteins or lipids. This recognition allows cells in an embryo to sort themselves into tissues and organs. Also enables cells o


Third function of membrane proteins. It forms this between cells


Fourth function of membrane proteins. Many membrane proteins are WHAT. Shows hows enzymes may work as a team to carry out sequential steps in a pathway.


Fifth function of membrane proteins. Act as this for chemical messengers from other cells. It has a shape that fits a specific messenger, such as a hormone.


Sixth function of membrane protein. Selective permeability allows substances to cross more easily than others.

selective permeability

Membrane proteins allow substances to cross more easily than others. They have a hydrophobic interior. Nonpolar, hydrophobic molecules can easily pass through membranes.


tendency for particles of any kin to spread out evenly in a space moving from high concentration to low concentration

thermal motion

(heat). Molecules vibrate and move randomly in diffusion. It requires NO WORK.

concentration gradient

An increase or decrease in the density of a chemical substance in an area. Cells often maintain concentration gradients of ions across their membranes. When a gradient exists, substances tend to move from where they are more concentrated to where they are

passive transport

Driving force of concentration gradient. The diffusion of a substances across a biological membrane, without any energy.


diffusion of water molecules across a selectively permeable membrane. (Allows some substances to cross more easily than others)

direction of osmosis

determined by the difference in total solute concentration, not by the nature of the solutes.


describes the ability of a solution to cause a cell to gain or lose water. The tonicity of a solution depends on its concentration of solutes that cannot cross the plasma membrane relative to the concentrations of solutes in the cell.


A solution where the cel's volume remains constant. It remains equal and the cell gains water as the same rate that it loses it. Ex.) IV fluids must be isotonic to blood cells and Sea animals are isotonic to sea water.


A solution with a solute concentration lower than that of the cell. The cell gains water, swells, and bursts.


a solution with a higher concentration. The cell shrivels and dies from water loss.


A cell's way to survive in a hypotonic and hypertonic environment. Ex by preventing excess of loss of water.

plant cell isotonic

limp (flaccid)

plant cell hypotonic

firm (turgid)

plant cell hypertonic

(plasmolysis) plant cell loses water and shrivels. Plasma membrane moves from cell wall.

faciliated diffusion

The name of this process: protein makes it possible for a substance to move down its concentration gradient. (Does not require energy- passive transport)

transport protein

provides a hydrophilic channel that some molecules use as a tunnel through the membrane. Another type binds its passenger changes shape, and releases its passenger on the other side. It helps move susbstances across the membrane. The greater number of tra


rapid diffusion of water into and out of cells is made possible by this.

How do transport proteins contribute to a membrane's selective permeability

How do transport proteins contribute to a membrane's selective permeability: Transport proteins are specific for the solutes they transport. Thus, the numbers and kinds of different transport protein molecules embedded in the membrane affects its permeabi

active transport

a cell must expend energy to move a solute against its concentration gradient. That is, across a membrane toward the side where the solute is more concentrated. It allows a cell to maintain concentrations of small molecules that are different from concent

Active transport process

Active transport process: 1. Begins when solute attaches to a specific binding site on the transport protein 2. ATP transfers one of its phosphate groups to the transport protein 3. Protein changes shape so the solute is released on the other side of the


used by cells to export bulky materials like proteins and polysaccharides. A transport vesicle filled with macromolecules from Golgi apparatus moves to the plasma membrane. Once there, the vesicle fuses with the plasma membrane, and the vesicle's contents


Opposite of exocytosis. A cell takes in substances. A depression in the plasma membrane pinches in and forms a vesicle enclosing material that had been outside the cell.


cellular eating". A cell engulfs a particle by wrapping extensions called pseudopodia around it and packaging it within a membrane-enclosed sac large enough to be called a vacuole. The vacuole then fuses with a lysosome.


cellular drinking". The cell 'gulps' droplets of fluid into tiny vesicles. Not specific.

receptor-mediated endocytosis

very specific. Receptor proteins for specific molecules are embedded in the membrane. Use: take in cholesterol from the blood for synthesis of membranes and as a precursor for other steroids. Cholesterol circulates in the blood in particles called low-den

As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis?

As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis?: Exocytosis. When a transport vesicle fuses with plasma membrane, the vesicle membrane becomes part of the plasma membrane.


capacity to perform work or capacity to rearrange mater.


Performed when an object is moved against an opposing force such as gravity of friction

Kinetic energy

energy of motion. Moving objects can perform work by transferring motion to other matter.


(thermal energy) a form of kinetic energy associated with the random movements of atoms or molecules.

Potential energy

stored energy that an object possesses as a result of its location or structure. Ex.) Cyclist on the top of hill

Chemical energy

potential energy available for release in a chemical reaction. It is the most important type of energy for living organisms- it is the energy that is available to do the work of the cell.


study of energy transformations that occur in a collection of matter

first law of thermodynamics

energy in the universe is constant. Energy can be transferred and transformed, but it cannot be created or destroyed. Ex.) Light bulb converts electricity to light energy


a measure of disorder/randomness. Some energy becomes unusable- unavailable to do work.

second law of thermodynamics

energy conversions increase the entropy (disorder) of the universe

How does the second law of thermodynamics help explain the diffusion of a solute across a membrane?

How does the second law of thermodynamics help explain the diffusion of a solute across a membrane?: It results in equal concentrations of solute molecules, which is a more disordered arrangement (high entropy) than a high concentration on one side and a

exergonic reaction

A chemical reaction that releases energy. Begins with reactants whose covalent bonds contain more energy than those in the products. The reaction releases to the surroundings an amount of energy equal to the difference in potential energy between the reac

cellular respiration

a chemical process that uses oxygen to convert the cheical energy stored in fuel molecules to a form of chemical energy that the cell can use to perform work.

endergonic reaction

yield products that are rich in potential energy. ("Energy inward")- reaction starts out with reactant molecules that contain relatively little potential energy. Energy is absorbed from the surroundings as the reaction occurs, so the products of an enderg


total of an organism's chemical reactions (exergonic and endergonic reactions)

metabolic pathway

a series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds

energy coupling

the use of energy released from exergonic reactions to drive essential endergonic reactions- a crucial ability of al cells. (ATP is key)


powers all forms of cellular work. Consists of adenine (nitrogenous base) and ribose (five carbon sugar) and a chain of three phosphate groups (triphosphate).


ATP transfers its 3rd phosphate group to some other molecule.

3 types of cellular work

chemical, mechanical, and transport

chemical work

the phosphorylation of reactants provides energy to drive the endergonic synthesis of products

mechanical work

the transfer of phosphate groups to special motor proteins in muscle cells causes the proteins to change shape and pull on actin filaments, in turn causing the cells to contract

transport work

ATP drives the active transport of solutes across a membrane against their concentration gradient by phosphorylating certain membrane proteins

ATP cycle

1. energy released in exergonic reactions is used to generate ATP from ADP. 2. Endergonic process- a phosphate group is bonded to ADP. A cell at work uses ATP continuously, and the ATP cycle runs again.

Explain how ATP transfers energy from exergonic to endergonic processes in the cell?

Explain how ATP transfers energy from exergonic to endergonic processes in the cell?: Exergonic processes phosphorylate ADP to form ATP. ATP transfers energy to endergonic processes by phosphorylating other molecules

energy of activation

There is an energy barrier that must be overcome before a chemical reaction can begin. Energy must be absorbed to contort or weaken bonds in reactant molecules so that they can break and new bonds can form. "Amount of energy needed to push the reactants o


add WHAT to speed up reactions?


proteins that function as biological catalysts, increasing the rate of a reaction without being consumed by the reaction. An enzyme speeds up a reaction by lowering the Ea barrier


specific reactant that an enzyme acts on.

Active site

a pocket or groove on the surface of the enzyme formed by only a few of the enzyme's amino acids. The rest of the protein maintains the shape of the active site. Enzymes are specific bc their active sites fit only specific substrate molecules.

catalytic cycle of an enzyme

1. Sucrace starts with an empty active site. 2. Sucrose enters the active site, attaching by weak bonds. The active site changes shape slightly so that it embraces the substrate more snugly (induced fit). 3. The strained bond reacts with water, and the hi


High temperature denatures the enzyme altering its specific shape and destroying function. Enzymes work best at human body temp (95-104 degrees F) or 37 degrees celsius.


Enzyme pH is near neutrality: 6-8


nonprotein helpers that enzymes require. Inorganic- zinc, iron, cooper


organic cofactor molecules. Most vitamins are important in nutrition bc they function as coenzymes.


a chemical that interferes with an enzyme's activity

competitive inhibitor

reduces an enzyme's productivity by blocking substrates from entering the active site.

noncompetitive inhibitor

does not enter the active site. Instead, it binds to the enzyme somewhere else, and its binding changes the shape of the enzyme so that the active site no longer fits the substrate.

irreversible inhibitators

Toxins and poisons are WHAT? The inhibition of this enzyme leads to rapid paralysis of vital functions and death. Pesticides are toxic to insects bc they also irreversibly inhibit this enzyme.

feedback inhibition

a method of metabolic control in which a product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway

What is the advantage of the feedback inhibition to a cell?

What is the advantage of the feedback inhibition to a cell?: It prevents the cell from wasting valuable resources by synthesizing more of a particular product than is necessary.