Unit 4- Biochemistry, Energy, Enzymes

4b- Energy, Enzymes, ATP

Objectives!

• Today, you will model the activity of an enzyme and how it functions to catalyze biochemical reactions.

• Standards: H.B.2A The essential functions of a cell involve chemical reactions that take place between many different types of molecules (including carbohydrates, lipids, proteins and nucleic acids) and are catalyzed by enzymes.

Bellwork• What is the role of an enzyme in

the body?– What does an enzyme lower?

• What factors affect enzymatic activity?

• In the toothpick lab, what did the toothpick represent? What did your hands represent? What did the broken toothpicks represent?

Chemical Reactions• A chemical reaction breaks down some

substances and builds other substances

2H2 + O2 ------> 2H2O

• Biochemical Reactions allow organisms to grow, develop, reproduce, & adapt.

Reactants

Products

Chemical Reactions• Chemical Reactions can occur when reactants collide

with enough energy to react. – The amount of energy that is sufficient for a particular

chemical reaction to occur is called the activation energy. – Sometimes, a chemical reaction must absorb energy for the

reaction to start (often in the form of heat)– Energy (as heat or light) can also be given off as a result of

biochemical reactions• Ex- Cellular Respiration, Bioluminescence

Energy as heat/light

Cellular Respiration

Bioluminescence

Chemical Reactions• There are several factors that affect the rates of

biochemical reactions. – Temperature – gaining or losing heat energy– pH – most organisms need to be kept in a small range of acidity

for reactions to occur• Buffers within an organism regulate pH so homeostasis is

maintained• A small change in pH can disrupt cell processes

– Catalysts – substance that changes the rate of a reaction or allows the reaction to occur (activate) at a lower temperature• Work by lowering the activation energy of a reaction • Catalysts are not consumed or altered in a reaction, can be

used over and over

Enzymes• Enzymes are proteins that serve as catalysts in living

things. – Enzymes are very specific.

• Each particular enzyme can catalyze only one chemical reaction by working on one particular reactant (substrate)

– Enzymes are involved in many of the chemical reactions necessary for organisms to live, reproduce, & grow.• Examples: digestion, respiration, reproduction, movement, and cell

regulation – Enzymes speed up reactions that otherwise would occur too

slowly at the body’s temperature• Reactions are able to occur at lower temperatures

Enzyme Names

• Enzymes will often end in the suffix –ase• The beginning of the name often tells you the

substrate of the enzyme• Substrate: what an enzyme acts upon (the

reactant)– Examples:

• Amylase breaks down amylose (a component of starch)• Lactase breaks down lactose (a sugar in dairy products)

– Lactose intolerant people lack the enzyme lactase

Induced Fit Model of Enzyme Action

• Enzyme reactions depend on a physical fit between the enzyme & the substrate– Lock & key hypothesis– Induced fit- enzyme

changes shape as the substrate molecules get close. • change in shape is

“induced” by the substrate

Induced Fit Model of Enzyme Action• Substrate fits at the active

site – Enzyme-substrate complex;

reaction intermediate – This formation has a lower

activation energy than the reaction between reactants without a catalyst

• Reaction occurs and products released.

• Enzyme is back to its original shape & ready to act again

Factors that Affect Enzyme Activity• Temperature

– Each type of enzyme has a temperature range at which it works best.

– Enzyme activity increases as the environment reaches that ideal temperature

– Activity slows outside of that range.• pH

– Enzymes have a specific pH range at which they will work

• At an extreme temperature or pH, an enzyme can denature (change shape and become ineffective)

Factors that Affect Enzyme Activity• Enzyme Concentration

– If the amount of substrate stays the same, the rate of reaction will increase if the enzyme concentration increases

– Reaction rate will drop if it runs out of substrate

• Substrate Concentration– If the amount of enzyme stays the

same, the rate of reaction will increase if the substrate concentration increases

– Reaction rate will level off when all of the enzymes are working

Constant enzyme concentration

ATP• Life processes require a constant

supply of energy. – Cells use energy that is stored in the

bonds of certain biological molecules. – Adenosine triphosphate (ATP) is a

molecule that transfers energy from the breakdown of food molecules to cell processes.

– ATP supplies energy that can be used quickly and easily by cells

ATP Structure

• A molecule of ATP is composed of 3 parts:– A nitrogen base (adenine)– A sugar (ribose)– Three phosphate groups

that are bonded together by “high energy” bonds

ATP ADP• The energy stored in ATP is released when a

phosphate group is removed from the molecule. – This energy drives the cell’s metabolism.– When the phosphate is removed, ATP becomes ADP-

adenosine diphosphate.– ATP ADP + phosphate + energy available for cell processes

ADP ATP• To supply the cell with energy, ADP is continually

converted to ATP during the process of cellular respiration. – As the cell requires more energy, it uses energy from the

breakdown of food molecules to attach a free phosphate group to an ADP molecule to make ATP.

– ADP + phosphate + energy from breakdown of food molecules ATP

ATP Recap• ATP is consumed by energy-requiring

processes and can be generated by energy-releasing processes. – ATP transfers energy between separate

biochemical reactions in the cell. – ATP is the main energy source for the majority of

cellular functions• Including: synthesis of macromolecules like DNA and

proteins• It also plays a key role in the transport of

macromolecules across cell membranes

Watch!

• https://www.youtube.com/watch?v=JeGx2Nalhtg