Energy flow

what do living organisms need to do to carry out the functions of life? (3) How is it accomplished?

continually capture/acquire, store, and use energy to carry out the functions of life

All 3 are accomplished through cellular chemical processes (eg cellular respiration)

Cells are a _____ that obey ____ & ______

Cells are CHEMICAL MACHINES that obey FUNDAMENTAL CHEMICAL & PHYSICAL LAWS OF NATURE

what is the sum of a cell’s chemical reactions?

metabolism

what is energy?

ability to do WORK

what is work

transfer of energy from one body or place to another

what do cells use catabolic reactions for? How does this happen?

Purpose: to convert CHEMICAL POTENTIAL ENERGY → KINETIC ENERGY

process:

• hydrolysis of ATP transfers chemical potential energy (stored energy) → protein pump to move particles through a membrane (kinetic energy)

What does anabolic reactions do? How does it do this?

Purpose: convert kinetic energy into chemical potential energy

How: photosynthesis captures light energy and stories it as chemical potential energy

What do biological molecules (carbs, proteins, lipids, etc) have stored in their chemical bonds?

potential energy

What is cellular respiration?

the process by which a cell enzymatically breaks these energy containing bonds to release their energy and harness it to fulfill a cellular function

What are 3 things about bond energy?

• measure of the stability of a COVALENT BOND

• equal to the minimum amount of energy required to break the bond

• the stronger the bond, the more energy required to break it

In chemical reactions when is energy added? What state is this?

• when the bonds between reactants are broken → reach a transition state

When is energy released in chemical reactions?

• when product bonds form and if the bonds are more stable than the reactant bonds

what is thermodynamics?

• study of energy transformation

what do the laws of thermodynamics describe?

• what energy transformations can and cannot do

What does the first law of thermodynamics state? (3)

The total energy in a closed system is CONSTANT.

Energy cannot be created or destroyed. (conservation of energy)

It can only be converted from one form to another

What happens when a chemical reaction occurs? What is something important to remember about this?

What happens:

• some of the energy can be transferred from one type of energy to another/others

eg: potential → thermal & light

Note:

• the transfer is not 100% efficient, some energy is ALWAYS lost as WASTE (does not perform work)

What is wasted energy? What type of energy is it? What is important to remember abt it?

What: does NOT perform WORK

Type:

• Can be any type, but usually heat (thermal) energy is referred to as waste (enthalpy)

Note:

• ultimately, all energy in the universe will be transformed into heat energy

What is the 2nd law of thermodynamics about? (2) What does it say?

About:

• transformation of potential energy into heat, or random arrangement of energy

• RANDOMNESS IS CONTINUOUSLY INCREASING

Statement:

• the total energy of an ISOLATED SYSTEM ALWAYS increases over time or remains CONSTANT

• entropy can never be negative

What is entropy? What is it’s relation to the universe?

The disorder of the universe. It is CONTINUOUSLY increasing.

For what must energy be spent to achieve?

• must be spent to RETAIN ORDER

• spending of energy usually releases heat → increases entropy elsewhere

What is free energy?

portion of the systems energy that can perform work

What is a open, closed, and isolated system?

• Open: Both matter and energy can enter and leave.

• Closed: Only energy can enter and leave.

• Isolated: Neither matter or energy can enter or leave.

Why is free energy “free”?

• this is the energy that can perform WORK, not because there is no energy cost to the system

What is activation energy?

Amount of energy needed to strain and break reactant bonds, causing a reaction to proceed

What is an EXERgonic reaction?

Process with a net RELEASE of free energy

eg: burning paper (needs initial energy input; activation energy, once it starts it releases more energy than it requires to begin)

What is an ENDERgonic reaction?

Process with a net STORAGE of free energy

eg: most synthesis reactions

What kind of reactions do living systems depend greatly on? What does this reaction type do?

ENDERgonic reactions

Purpose: build larger organized structures that create the phenomenon called life

Which reaction “violates” the 2nd law of thermodynamics and why?

ENDERgonic reactions (synthesis; anabolic; organized) because the 2nd law says that entropy increases, but endergonic reactions decrease energy (organization of molecules)

What do endergonic reactions need to occur? define that term

they must be COUPLED: energy released by one reaction drives the 2nd reaction

explanation:

• building protein needs energy (endergonic), it cant happen ON ITS OWN bc it needs an ENERGY INPUT

• solution → paired with another reaction

so another reaction that does not violate the 2nd law of thermodynamics

THEREFORE:

even though it can decrease entropy (more organized molecule), the coupled process involved energy transfers that INCREASE entropy in the SURROUNDINGS → entire couple process considered = total increase in entropy

In biological systems what is the second reaction? (coupled to the endergonic) How does it work?

ALWAYS the HYDROLYSIS of an ATP molecule

Purpose:

• ATP hydrolysis RELEASES the energy that “POWERS” the endergonic reactions

• also INCREASES ENTRYOPY of the overall chemical changes so that the 2nd law is not violated

Why is ATP important in living cells and endergonic reactions? How does it work?

because it is the PRIMARY source of FREE energy

process:

when free energy is needed, and enzyme (ATPASE) hydrolyses the terminal (end; 3rd) phosphate from the ATP molecule and release 31kJ/mol free energy

What happens when endergonic and exergonic reactions are coupled?

• there is a release of MORE FREE ENERGY than can be stored in the PRODUCTS of the endergonic reaction

some of the extra energy is lost as HEAT

What something to remember about the coupled exergonic reactions

increase in entryopy from the hydrolysis of ATP is ALWAYS GREATER than the DECREASE IN ENTROPY from the reaction it is COUPLED WITH

What is oxidization?

process of LOSING ELECTRONS

oxidized = lose electrons

What is reduction?

process of GAINING ELECTRONS

reduced = gain electrons

What are redox reactions?

reactions that involve the transfer of electrons between two substances, where one substance is OX-IDIZED and the other is RED-UCED

What are electron carriers? What are 2 examples in metabolic processes?

compounds that PICK UP electrons from energy RICH compounds and then DONATE them to LOWER ENERGY compounds

example:

NAD+ and FAD (ELECTRON TAXIS)

• NAD⁺ and FAD: pick up electrons

• NADH and FADH₂: carry electrons