Immagini e concetti della biologia Sylvia S. Mader Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

A5 - Cellular Activity Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Energy has different forms Energy is as the ability to do work Radiant energy Chemical energy Mechanical energy Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Energy has different forms Radiant Energy (or solar energy) is the energy coming from the sun and is associated to electromagnetic waves. Chemical Energy is the energy contained into organic molecules in the form of specific chemical bonds. Mechanical Energy is the energy associated with any type of motion. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Energy has different forms Heat and is the energy related to the motion of microscopic systems such as atoms, ions and molecules. Calorie = the amount of energy needed to increase the temperature of 1 g of water by 1 °C. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Potential energy or kinetic energy? The energy of a body due to the position. Is a stored energy. Kinetic energy The energy of a body due to its motion. Is the energy in action. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

The two laws of thermodynamics Thermodynamics is a branch of sciences concerned with heat flows and its relations to energy and work. Principles applied to transformation of energy are know as “Laws of thermodynamics”. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

The two laws of thermodynamics I law of Thermodynamics (or law of conservation of energy) “Energy can change form within the systems (solar energy can become chemical energy), but it can be neither created nor destroyed”. Solar energy Chemical energy Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

The two laws of thermodynamics II law of Thermodynamics “Energy cannot change from one form to another without a loss of energy in the form of heat. This heat increases the entropy (disorder) of the system”. Solar energy Chemical energy HEAT Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

The two laws of thermodynamics Many important biological reactions involve a loss of energy as heat. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Energy flow and transformations Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Cellular work is powered by ATP ATP (Adenosine Triphosphate) is a nucleotide that consists of: A double ring of carbon and nitrogen atoms called adenine; A small five-carbon carbohydrate called ribose; Three phosphate units linked together by covalent bonds. Adenine Ribose Phosphate groups Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Cellular work is powered by ATP The breaking reaction products (ADP + P) are more stable than the molecule of ATP. ATP + ADP P Adenosine Triphosphate Diphosphate Hence, when ATP breaks down to ADP + P, energy is released. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

ATP cycle ATP ➞ ADP + P exergonic reaction (releases energy) ADP + P ➞ ATP endergonic reaction (requires energy to occur) Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

ATP hydrolysis is always associated with endergonic reactions. Coupled reactions Reactions are coupled when the energy required for a reaction (endergonic) is provided by an exergonic reaction. ATP hydrolysis is always associated with endergonic reactions. Muscular contraction occurs if associated with ATP hydrolysis Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Enzymes are catalysts Enzymes speed up the reaction by decreasing the energy of activation (Ea) of a given reaction. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Factors affecting enzymes activity Substrate concentration Temperature pH Cofactors as vitamins and coenzymes Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Metabolic pathways and inhibition Metabolic pathways are series of chemical reactions occurring within a cell. Enzyme inhibition occurs when a substance binds to an enzyme and decreases its activity. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Enzyme inhibition Noncompetitive inhibition: inhibitor binds to an enzyme at the allosteric site (a site other than the active site). Competitive inhibition: an inhibitor and a substrate compete for the enzyme’s active site. In the case of some inhibitors such as cyanide, sarin gas or warfarin (rat poison) enzymatic inhibition can spell death. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Plasma Membrane is dynamic Proteins are embedded in a phospholipid bi-bilayer in a “fluid mosaic membrane”. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Membrane Proteins have various functions Channel and carrier proteins respectively allow and assist the passage of molecules through the membrane. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Membrane Proteins have various functions Cell recognition proteins help the cell recognize foreign invaders. Receptor proteins bind specific molecules. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Membrane Proteins have various functions Enzymatic proteins carry out metabolic reactions while junction proteins assist cell-to-cell communications. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Diffusion Some small molecules or ions such as CO2, O2, C6H12O6 and H2O, move across the plasma membrane by diffusion, a passive transport process. There are two types of diffusion: Simple diffusion Facilitated diffusion Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Simple diffusion Molecules in solution move down a concentration gradient until they equally distribute. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Facilitate diffusion Carrier proteins facilitate diffusion of nonlipid-soluble substances across the membrane. Facilitate diffusion does not require energy. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Osmosis Water moves into a region of higher solute concentration, in order to equalize the solute concentrations on the two sides of the membrane. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Osmosis Cells placed in an isotonic solution (iso = same) neither gain nor lose water. Cells place in a hypotonic solution (ipo = less) gain water. Cells placed in a hypertonic solution (iper = more) lose water. Osmosis effects on animal and plant cells Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Active transport In order to move a substance against its concentration gradient the consumption of energy (ATP) is required. Carrier proteins involved in active transport are called pumps. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Endocytosis Endocytosis is the process by which cells absorb big particles by engulfing them. Most biologically important substances are large molecules that cannot pass through the plasma membrane. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Exocytosis Exocytosis is the process by which vesicles transport substances as digestive enzymes and hormones out of the cell. Transport of massive particles (macromolecules) in and out the cell membrane requires the use of vesicles. Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

Malfunctions in the membrane proteins Malfunctioning plasma membrane proteins can cause human diseases such as: Cystic fibrosis is caused by a malfunctioning gene of the channel protein called FC-protein malfunctioning FC-channel protein Accumulation of mucus in the respiratory tract H2O and Cl- are trapped inside the cell Diabetes type 2 Cystic fibrosis Color blindness Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012