Biology 105 Exam 2

Review

What are membranes made of

→ lipids

→ proteins

According to the fluid mosaic model of membrane structure, a mosaic of ____ floats in or on a fluid ____ _______

proteins; phospholipid bilayer

what is something that all cells have

plasma membrane

Proteins which are embedded in the membrane are called ______ membrane proteins, while proteins which are attached to the surface of the membrane are called _______ proteins

intergral; peripheral

cells continually exchange materials and information with their environment. This exchange is crucial ______

for all processes occurring in a cell

all cell membranes contain a phospholipid ______ which provides flexible matrix and a barrier to _______

bilayer; permeability

The thin structure made of a bilayer of lipids with embedded proteins that surrounds all cells is called the ____ ______

plasma membrane

what is a defining feature of biological membranes

the presence of two phospholipid sheets

What best describes the fluid mosaic model of a membrane

proteins float in or on a fluid lipid bilayer

which part of an integral membrane protein is found in contact with the interior of the lipid bilayer

non-polar segment

what is one of the main functions of the membrane’s phospholipid bilayer?

to impose a barrier to permeability

What can relatively easily move laterally within the plasma membrane

phospholipids and unanchored proteins

what is the effect of cholesterol on a plasma membrane at lower than physiological temperatures

it makes the membrane more fluid

transport that occurs without a cell expending any of its own energy is called ____ transport

passive

the lack of double bonds in phospholipids with saturated fatty acids allow them to pack together tightly, and therefore the membrane is _______ fluid. Kinks introduced by double bonds in lipids with unsaturated fatty acids prevent from packing together tightly, and therefore the membrane is ______ fluid.

less; more

When the concentration of a substance varies from one region to another, the substance is exhibiting a(n) ______

concentration gradient

What describes passive transport?

it does not require an expenditure of energy by the cell itself

Net movement of a substance from a region where it has a higher concentration to a region where it has a lower concentration is called _______

diffusion

oxygen diffuses across the plasma membrane due to what?

all oxygen molecules are in constant random motion

what is the permeability of a typical cell membrane to a large polar molecules

very limited permeability

when concentration of a substance on one side of the membrane is different from its concentration on the other side of the membrane, the substance is said to exhibit a concentration _______

gradient

Diffusion that occurs through a channel protein or a carrier protein is called _______ diffusion

facilitated

Due to the constant random motion of its atoms and molecules, a substance will exhibit net movement from a region where it has a higher concentration to a region where it has a lower concentration. This net movement is called ______

diffusion

plasma membranes allow some substances to pass through easily while other substances only pass through very slowly or not at all. For that reason, plasma membranes are said to be ______

selectively permeable

how does a lipid composition affect membrane fluidity

→ saturated fatty acids tend to make the membrane less fluid because they pack together well

→ sphingolipids tend to make the membrane less fluid

substances diffuse from areas of higher concentration to areas of lower concentration because their molecules (or ions) _______

exhibit constant random motion

when a channel protein or carrier protein assists in diffusion, what is then observed

facilitated diffusion

cellular ______ are said to be selectively _______ because they allow some substances to pass through easily, while other substances pass through very slowly or not at all

membranes; permeable

the cytoplasm of a cell contains ions and molecules dissolved in ______

water

an aqueous solution with a LOWER concentration of solutes will have a ____ concentration of free water molecules

higher

Osmosis occurs when there is a selectively permeable membrane and it refers to the diffusion of _______

water

the most abundant molecule in the cytoplasm is the _____ molecule

water

what is the underlying cause of diffusion

the constant random motion of all atoms and molecules

if you compare two aqueous solutions which differ in the amount of solutes dissolved, the aqueous solution with a HIGHER concentration of solutes will have ______

a lower concentration of free water molecules

if two solution have unequal concentrations of solutes, which one will be considered hypertonic?

the solution with a higher solute concentration

the diffusion of water across a selectively permeable membrane is called _____

osmosis

what would occur if a cell is placed in a hypotonic solution?

→ the cell will swell

→ there will be a net movement of water into the cell

what happens to the hydrostatic pressure inside a cell if it is transferred from a hypertonic environment to a hypotonic environment

it will increase

how do active and passive transports differ?

→ only active transports relies on an expenditure of energy by the cell itself, usually from ATP

→ only active transport can move a substance against its concentrations gradient

if two solutions have the same concentration of solutes (all solutes), they are ____ solutions

isotonic

carrier proteins that transport 2 different types of molecules or ions may either ______ or aniporters

symporters

if a cell is placed in a hypertonic solution, what occurs?

→ the cell will shrink

→ there will be net movement of water out of the cell

if a cell is transferred from a hypotonic environment to a hypertonic environment, the hydrostatic pressure inside the cell will ______

decrease

while ____ transport requires the cell to expend some of its own energy, _____ transport does not

active; passive

how can a cell move a substance out of its cytoplasm if that substance is found in a higher concentration in the extracellular fluid?

through active transport

what is the name of the carrier proteins that transport a single type of molecule or ion?

uniporters

how do you describe how ATP is used to drive active transport across the plasma membrane?

ATP can be used directly or indirectly

The sodium potassium pump actively pumps _________

sodium ions into the cell and potassium ions out of the cell

Energy released from the hydrolysis of ATP is used to change the confirmation of the sodium-potassium pump which results in changes in ______

the proteins affinity for Na+ and K+

Why is active transport such an important cell process

only active transport can move a substance from an area where it has a lower concentration to an area where it has a higher concentration

what is the branch of chemistry concerned with energy changes

thermodynamics

the use of ATP in active transport _______

may be direct or indirect

What are the actions of the sodium-potassium pump

→ it is an active transport mechanism

→ it moves sodium ions and potassium ions across the membrane in opposite directions

what is the immediate source of the energy needed to power the sodium potassium pump?

hydrolysis of ATP

How can a cell move a substance out of its cytoplasm if that substance is found in a higher concentration in the extracellular fluid?

through active transport

what is the term for the ability to do work?

energy

the branch of chemistry that studies ______ changes is called thermodynamics

energy

How does ATP used to drive active transport across the plasma membrane

ATP can be used directly or indirectly

what are the two main states of energy

kinetic energy and potential energy

work in the cell or in the physical world can only be done with expenditure of ______; it is defined as the capacity to do work

energy

How is energy used in chemical reactions

energy stored in certain chemical bonds can be used to make new bonds

during a chemical reaction, which molecules become oxidized

molecules that have an electron removed

the use of ATP in active transport _____

may be indirect or direct

in broad terms, energy can exist in two states: ____ energy and _____ energy

kinetic; potential

when a molecule has fewer electrons and less energy than reduced reactions it is….

a oxidized molecule

redox reaction is a term used to describe a(n) _______ - ________ reaction

oxidation; reduction

_______ stored in the chemical bonds of a molecule can be used to make new bonds in different molecule

energy

during a chemical reaction which molecules become reduced

molecules that have one or more electrons added

for a molecule that participates in a redox reaction, the ______ form of the molecule has a higher level of potential energy than the ______ form.

reduced; oxidized

what occurs during a redox reaction?

when an atom or molecule is oxidized, the electron that is removed is transferred to another atom or molecule, which is thereby reduced

the energy available to do work in a system is called _____ energy

free

Endergonic reactions

→ endergonic reactions have a positive change in free energy

→ the products have a higher free energy than the reactants

→ endergonic reactions are not spontaneous

exergonic reactions have a _______ change in free energy, and endergonic reactions have a ______ change in free energy

negative; positive

what is the term used to describe the energy of a system that is available to do work?

free energy

Exergonic reactions

→ exergonic reactions release energy during product formation

→ exergonic reactions are spontaneous

_______ energy is the energy required to destabilize existing chemical bonds and initiate a chemical response.

activation

a reaction that requires an input of energy is said to be a(n) ________ reaction

endergonic

how does the change in free energy differ between exergonic and endergonic reactions?

exergonic reactions have a negative change in free energy, whereas endergonic re-actions have a positive change in free energy

the energy available to do work in a system is called ______ energy

free

a reaction is said to be ____ when it releases excess free energy and tends to proceed spontaneously

exergonic

in order to be initiated, all chemical reactions, even exergonic ones, need ____

activation energy

what type of reaction releases free energy

exergonic

all cells use a molecule called ____ to carry and release energy cyclically

ATP

what nitrogenous base is a component of ATP

adenine

phosphate bonds in ATP are high energy bonds, because they are _____

unstable

the hydrolysis of ATP has a _______

negative delta G

what molecule is a common energy source for living organisms?

ATP

which of the ATP’s phosphate bonds is hydrolyzed in most cellular reactions

the outermost

which characteristic of ATP is responsible for its high energy bonds `

the repulsion of the negative phosphate groups

hydrolysis of which covalent bonds in ATP releases a considerable amount of energy

phosphate-phosphate bonds

how much energy is released when the outermost phosphate bond of ATP is hydolyzed under standard conditions

7.3 kcal/mol

is any energy released during ATP hydrolysis and if so, how much?

yes, a considerable amount of energy is released

What is included in metabolism?

both the synthesis and breakdown of organic molecules

What is the general role of anabolic reactions in the metabolism of a cell?

anabolic reactions are involved in the synthesis of larger molecules from smaller precursor molecules

Cells harvest energy during ________ reactions and expend energy during ______ reactions

catabolic; anabolic

Metabolic reactions are classified into two main categories. Of those two main categories, what type of reactions are involved in the harvest of energy by breaking down larger molecules into smaller molecules

catabolic

Each ______ in a biochemical pathway acts on the products of the previous reaction

enzyme

Metabolism…

refers to the sum of all chemical reactions that occur within an organism

What type of reactions are involved in the synthesis of larger molecules from smaller precursor molecules inside of living cells?

anabolic

Why are metabolic pathways regulated

→ By regulating metabolic pathways, cells conserve raw materials

→ By regulating metabolic pathways, cells waste less energy

→ regulation allows cells to operate efficiently