Lecture 3 - Energy, Catalysis, and Biosynthesis (EXAM 1)

catabolic and anabolic pathways

What constitutes the cell's metabolism?

heat

During catabolism, what is the major portion of the energy stored in the chemical bonds of food molecules dissipated as?

useful forms of energy

What is some of the energy not lost in catabolic pathways converted to that are needed to drive the synthesis of new molecules in anabolic pathways?

photosynthesis and cell respiration

What are complementary processes?

oxidation of organic molecules

How do cells obtain energy?

Photosynthesis

carried out by plants and photosynthetic organisms; uses the energy of sunlight to produce sugars and other organic molecules from the carbon atoms in CO2 in the atmosphere

Cell Respiration

takes place in most living organisms, including plants and photosynthetic algae and bacteria

-uses O2 to oxidize

-releases carbon atoms in the form of CO2

What does cell respiration use to oxidize organic molecules and what does it release back to the atmosphere?

useful chemical-bond energy

During cell respiration, what do organisms obtain that they need to survive?

billions of years of photosynthesis were required to release enough O2 to create an atmosphere that could support respiration

Why must photosynthesis have preceded cell respiration on earth?

carbon atoms

What cycles continuously through the biosphere?

by the photosynthetic activity of plants, algae, and bacteria

How are individual carbon atoms incorporated into organic molecules of the living world?

the atmosphere in the form of CO2

Organic molecules are consumed by animals and microorganisms and are ultimately restored to where?

organic molecules are oxidized by cells during respiration or burned by humans as fossil fuels

What happens before CO2 is restored to the atmosphere?

oxidation and reduction

What involves a shift in the balance of electrons?

reduced

When two atoms form a polar covalent bond, the atom that ends up with a greater share of electrons is said to be what?

oxidized

When two atoms form a polar covalent bond, the atom that with a lesser share of electrons is said to be what?

greater electronegativity

Electrons are attracted to the atom that has what?

partial negative charge

What does the reduced atom require?

partial positive charge

What does the oxidized atom require?

by successive replacement of its covalently bonded hydrogen atoms with oxygen atoms

How can a simple reduced carbon compound, such as methane, be oxidized?

it becomes progressively more reduced

What happens to a carbon atom as its oxygen atoms are replaced by hydrogens to yield methane?

activation energy

What to energetically favorable reaction require to get them started?

in the direction that causes a loss of free energy

What direction do chemical reactions proceed?

Enzymes

reduce the energy needed to initiate spontaneous reaction; lowers activation energy for catalyzed reaction

Delta G

changes in free energy occurring in a reaction; measures the amount of disorder caused by a reaction

Delta G = free energy (C+D) - free energy (A+B) (energy of product-energy of reactant)

What is the equation to find Delta G?

it measures how far away from equilibrium a reaction is

Why is Delta G useful?

negative

If a lot of energy is used in a reaction, what will the value of Delta G be?

Equilibrium

forward and backward reactions occur at equal rate and Delta G = 0

that the disorder of the universe can only increase

What do we know from the second law of thermodynamics?

when a chemical reaction occurs spontaneously

When is Delta G negative?

standard free-energy change

What is ΔG°?

Standard Free-Energy Change

represents the gain or loss of free energy as 1 mole of reactant is converted to 1 mole of product under "standard conditions"

-aqueous solution at a concentration of 1 M

-pH 7

What are considered standard conditions?

equilibrium point for reactions

What can enzymes not change?

Enzymes

speed up the forward and reverse rates of a reaction by the same amount

reach the same equilibrium point

Both catalyzed and uncatalyzed reactions will eventually do what?

catalyzed

Will a catalyzed or uncatalyzed reaction reach equilibrium faster?

Activated Carriers

can store and transfer energy in a form that cells can use

intracellular energy shuttles

What do activated carriers serve as?

by performing their function as go-betweens and carrying energy towards anabolic reaction

How do activated carriers link the release of energy from the breakdown of molecules (catabolism) to the energy-requiring biosynthesis of small and large organic molecules (anabolism)

ATP

What is the most widely used activated carrier?

ATP and ADP

The interconversion of what occurs in a cycle?

"high-energy" phosphoanhydride bonds

What are the two outermost phosphate groups in ATP held to the rest of the molecule by?

ADP and phosphate

Water can be added to ATP to form what?

46 and 54 kJ/mole

Inside a cell, the hydrolysis of the terminal phosphate of ATP yields what amount of usable energy?

formation of ATP from ADP

What reverses a hydrolysis reaction?

it must be coupled to a highly energetically favorable reaction

Because the formation of ATP (condensation reaction) is energetically unfavorable, what must happen for it to occur?

releases energy

What does going from ATP to ADP do?

the terminal phosphate of ATP

What can be transferred to other molecules?

it can convert energy-rich phosphoanhydride bond in ATP to a less energy-rich phosphoester bond in the phosphate-accepting molecule

Why is the phosphorylation reaction energetically favorable?

Delta G has a large negative value

What happens when a reaction is energetically favorable?

-synthesis of phospholipids

-breakdown of sugars

-metabolic processes

What are phosphorylation reactions involved in?

energy stored in ATP

What is often harnessed to joint two molecules together?

Activation

ATP transfers a phosphate to produce a high-energy intermediate

Condensation

the activated intermediate reacts to the product, a reaction accompanied by the release of phosphate

NADH and NADPH

What are two activated carriers of electrons?

phosphate group

Where is ATP high energy stored?

NADPH

an activated carrier of electrons that participates in oxidation-reduction reactions

when two electrons are removed from a substrate (oxidation)

How is NADPH produced?

because NADPH holds its hydride ion in a high-energy linkage

Why can the hydride ion of NADPH be easily transferred to other molecules?

by the transfer of a hydride ion from the activated carrier NADPH, plus a proton (H+) from solution

In a biosynthesis reaction, how is the reduction of the C=C bond achieved?

NADPH and NADH

What has different roles in cells?

relative concentrations of the carrier molecules

What influences NADPH and NADH affinity for electrons?

keeping reduced NADPH at a higher concentration than NADP+

What makes NADPH a stronger electron donor?

reducing agent for anabolic reactions

What can NADPH serve as because of it being a stronger electron donor?

cells keep the amount of reduced NADH lower than that of NAD+

What makes NAD+ a better electron acceptor?

effective oxidizing agent

What does NAD+ act as, accepting electrons generated during the oxidative breakdown of food molecules?

NAD+

What is an oxidizing agent for catabolic reactions?

NADPH

What is a reducing agent for anabolic reactions?