More about Cells Prokaryotes and Eukaryotes Organelles of Eukaryotes How do “things” get in and out of cells? – Bouncer – The gatekeeper

Movement of Molecules Active Transport PrimarySecondary Passive Transport DiffusionOsmosis Simple Diffusion Facilitated Diffusion

6.1 Energy Is Central to Life

Energy Is Central to Life All living things require energy. The sun is the ultimate source of energy for most living things. The sun’s energy is captured on Earth by photosynthesizing organisms, which then pass this energy on to other organisms in the form of food.

6.2 The Nature of Energy

What is energy? Energy can be defined as the capacity to bring about movement against an opposing force. - capacity to do work

Forms of Energy Energy can be conceptualized as either potential energy, meaning stored energy; or kinetic energy, meaning energy in motion.

Energy Conversions  Only ~1% of energy released by the sun that earth receives is captured and converted by plants. Converted into chemical bond energy  What happens to the other 99%? Mostly transformed into heat

Thermodynamics - study of energy First Law of Thermodynamics  Energy can never be created or destroyed.  It can only change forms. Second Law of Thermodynamics  Energy transfer will always result in a greater amount of disorder in the universe. (ENTROPY)  Every conversion of energy includes the transformation of some energy into heat.

ENTROPY A measure of the amount of disorder in a system The greater the entropy, the greater the disorder.

3. Mechanical energy 2. Heat energy 1. Chemical bond energy heat piston-driven flywheel coalmotion steam Total energy is constant. Entropy increases. Figure 6.2 Transformations of Energy

6.3 How Is Energy Used by Living Things?

How Is Energy Used by Living Things? Living things can bring about local increases in order through their metabolic processes. – build up larger molecules from smaller ones – They can, for example, build up more-ordered molecules (starches, proteins) from less ordered molecules (simple sugars, amino acids). However, it takes energy to do this.

Product (glycogen) contains more energy than the reactants (glucose) Product (glucose) contains less energy than the reactants (glycogen) endergonic reaction energy in glycogen molecule exergonic reaction energy out glucose molecules Figure 6.4 Energy Stored and Released

Endergonic and Exergonic Reactions Exergonic – breaking down molecules releases energy – starting set of molecules (reactants) have more energy than final set of molecules (products) – Energy is created by taking those molecules apart Endergonic –products have more energy than reactants – Energy is used to build molecules Coupled

ATP The molecule most often used in living things to power coupled reactions is ATP.

6.4 The Energy Dispenser: ATP

Structure of ATP

Figure 6.6 The ATP/ADP Cycle

Recycling in the Cell ADP + phosphate group + energy = ATP

Movie Time From 1:30 to 3:30

© 2011 Pearson Education, Inc. 6.5 Efficient Energy Use in Living Things: Enzymes

Enzymes are proteins that initiate and speed up chemical reactions (rate of reaction)

Figure 6.8 Enzyme Action – plays a role in metabolic pathways enzyme A enzyme C enzyme B substrates product

Movie Time Enzymes:

6.6 Enzymes and the Activation Barrier

Figure 6.9 Enzymes accelerate chemical reactions by lowering the activation energy (a) Without enzyme lactoseglucose + galactose activation energy without enzyme net energy released from splitting of lactose (b) With enzyme glucose + galactose lactose activation energy with enzyme net energy released lactase

Enzymes Accelerate Chemical Reactions Enzymes are catalysts. They bring about a change in their substrates without being chemically altered themselves.

Enzymes Accelerate Chemical Reactions Enzymes generally have a pocket into which the substrate fits. This pocket is the active site—that portion of an enzyme that binds with a substrate, thus helping transform it. SUBSTRATE

Substrate Binding – a little help from our friends In some cases, substrate binding is facilitated by coenzymes: molecules other than amino acids that facilitate the work of enzymes by binding with them

Coenzyme Accessory molecules Bind with enzymes Sit in the active site and chemically attract or repulse substrates Example: B vitamins

6.7 Regulating Enzymatic Activity

The rate at which an enzyme catalyzes a reaction is influenced by several chemical and physical factors. 1.Enzyme and substrate concentration 2.Temperature (optimal) 3.pH 4.Inhibitors or activators a.Competitive Inhibition b.Allosteric

Enzyme Inhibition: Movie Time

Why do some adults get sick when they drink milk?

Other Faulty Enzymes PKU Gaucher Disease – Lipids collect on spleen, liver, kidneys Tay Sachs Disease – Enzyme fold incorrectly & doesn’t break down a certain molecule – Damages nervous system