Bio-110 Chapter 5

Diffusion

A form of passive transport. Molecules move across the plasma membrane by crossing the lipid bilayer.

Facilitated diffusion

A form of passive transport. Molecules move across the plasma membrane using a transport protein.

Exocytosis

A vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell.

The molecule most directly involved in energy transfer within cells is _____.

ATP A molecule called ATP is responsible for fueling most energy-requiring reactions in cells.

Which of the following statements concerning enzymes is true and correct?

An enzyme is very specific in terms of which substrates it can bind. Only the specifically appropriate substrate will cause an induced fit, where the active site snugly binds to the substrate.

A plant cell placed in a(n) ___ solution will lose water and plasmolyze.

Hypertonic

Active Transport

Requires energy from the cell. Molecules move against their concentration gradient.

Which one of the following is an example of osmosis?

Water enters a plant by passing through the root cell membranes.

Calories are units of __________.

energy A calorie is the amount of energy required to increase the temperature of 1 gram of water by 1 degree C. Calories can refer to any type of energy, not just heat.

Through energy coupling, cells use _______, or energy-releasing, reactions to drive _________, or energy-requiring, reactions. The molecule ________ is the energy shuttle between these two types of reactions.

exergonic, endergonic, ATP

The secretion of neurotransmitters out of the nerve cell, from small vesicles at the end of the axon, can be considered an example of _____.

exocytosis

Mechanisms such as _________ enable precise control over a cell's _________ -- all of its chemical reactions.

feedback inhibition metabolism

Which of the following is the best example of a substance that contains chemical energy?

food that you eat Our body taps into the chemical energy of ingested foods to do work.

In cellular respiration, most energy is released and transferred to ATP when _____.

high-energy electrons "fall" to lower energy levels

In active transport,

molecules move across the plasma membrane against their concentration gradient.

Which of the following is highest in chemical energy?

one molecule of glucose

Some liver cells ingest bacteria, a function probably accomplished by _____.

phagocytosis In phagocytosis (cellular eating), a type of endocytosis, a cell engulfs a particle by wrapping pseudopodia around it and packaging it within a membrane-enclosed sac large enough to be classified as a vacuole.

A primary function of the cell membrane is to __________.

regulate the passage of materials into and out of the cell Transport proteins within the membrane are critical helpers.

Which is the best definition of energy?

the capacity to cause change Yes. Often this means the ability to do work.

The transport of molecules of a particular solute from inside an animal cell across the cell membrane to the extracellular fluid always requires energy when __________.

the concentration of the solute is lower inside the cell than outside it To pump a molecule across a membrane against its concentration gradient, the cell must expend metabolic energy, which is provided by ATP. This type of membrane traffic is called active transport.

Energy is conserved. This means that in any system, _____.

total energy input equals total energy output

The sodium-potassium pump uses energy from ATP to move sodium ions out of the cell, and potassium ions into the cell. This is an example of

Active Transport The sodium-potassium pump moves ions across the plasma membrane against their concentration gradients. This requires energy and is an example of active transport.

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of

Endocytosis In endocytosis, the plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell.

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via _____.

Endocytosis Endocytosis is the procedure that cells use to import large molecules across their membranes.

Which one of the following statements about energy is correct?

Energy cannot be created or destroyed. The law of conservation of energy states that energy cannot be created or destroyed.

A specific ______ speeds up each of a cell's chemical reactions.

Enzyme

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of

Facilitated Diffusion In facilitated diffusion, molecules use a transport protein to move across the plasma membrane. There is a net movement of molecules down the concentration gradient -- that is, there is a net movement of molecules from where they are more concentrated to where they are less concentrated.

There is a net diffusion of water out of an animal cell when it is placed in a(n) ______________solution.

Hypertonic

An animal cell placed in a(n)______________ solution will gain water, swell, and possibly burst.

Hypotonic

The ideal osmotic environment for a plant cell is a(n)__________ environment.

Hypotonic

A plant cell surrounded by a(n) ___ solution will be flaccid (limp).

Isotonic

The ideal osmotic environment for an animal cell is a(n)_____________ environment.

Isotonic

The diffusion of water across a selectively permeable membrane is called _____.

Osmosis This is a special case of passive transport.

Which of the following statements is true about passive transport?

Passive transport requires no expenditure of cellular energy. Passive transport is an example of diffusion down a concentration gradient, which is a spontaneous characteristic of matter.

Kinetic energy is energy in motion. Potential energy is _____ energy.

Stored energy

Endocytosis

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell.

The concentration of calcium in a cell is 0.3%. The concentration of calcium in the surrounding fluid is 0.1%. How could the cell obtain more calcium?

active transport For the cell to accumulate calcium, it must move calcium against its concentration gradient. Transport requiring an expenditure of energy is called active transport.

When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. This occurs regardless of whether the concentration of this molecule is higher inside or outside the cell. Using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane?

active transport Some transport proteins can move molecules against their concentration gradient in a process called active transport.

An enzyme is a protein that __________.

changes the rate of a metabolic reaction without being consumed by the reaction All catalysts, including enzymes, work by accelerating the rate of chemical reactions. They do this by lowering the activation energy. Catalysts are not consumed by the reaction and are therefore used repeatedly.

The movement of atoms, ions, or molecules from a region of higher concentration to regions of lower concentration is called _____.

diffusion Diffusion is the tendency of molecules to spread out in the available space. A substance will diffuse from an area of high concentration to an area of lower concentration.

There are three main types of cellular work: chemical, transport, and movement. Most of this work is powered by the transfer of a phosphate group from one molecule to another in a process known as .

phosphorylation

Water crosses the plasma membrane

through facilitated diffusion or diffusion. Water can cross the plasma membrane through the process of facilitated diffusion. However, water molecules can also cross the lipid bilayer directly.