Chapter 3 MATTER, ENERGY AND LIFE
Every organism uses matter and energy from its environment and transforms them into structures and processes that make life possible.
The physical and chemical principles that govern the universe also govern the composition and metabolic processes of living organisms.
Organisms are made of inorganic compounds and organic compounds.
MATTER AND FUNDAMENTAL PARTICLES
Matter is anything that has mass and takes up space.
Weight is a measurement of the pull of the Earth's gravity on an object.
· Weight changes with distance.
· Mass of an object is constant regardless of distance.
Matter is transformed and recombined but it doesn’t disappear. This is the principle of conservation of matter.
Elements are the simplest substances. They cannot be broken down into simpler substance by chemical reactions.
An atom is the simplest portion of an element that retains its chemical properties.
Each element has its own characteristic atom represented by a chemical symbol.
Subatomic particles: protons, neutrons and electrons.
The number of protons, atomic number, identifies the atom.
Protons carry a positive electrical charge; neutrons are electrically neutral, and electrons are negative.
The number of protons and neutrons determines the mass of the atom, atomic mass.
The mass of the electron is 1/1800 of the mass of a proton or neutron, and it is disregarded in calculating the atomic mass of an atom.
Isotopes of an element are atoms that have the same number of protons and different number of neutrons.
Some isotopes are radioactive and are called radioisotopes.
CHEMICAL BONDS
Atoms may combine chemically, bond, to form molecules.
Molecules of an element have atoms of the same kind, e.g. H2, N2.
A chemical compound is made of different type atoms, e.g. H2O, Ca(OH)2.
Molecular formulas describe the atomic composition of one molecule of the compound.
The forces that hold atoms together are called chemical bonds.
Each bond contains certain amount of energy called chemical energy. This energy can be released in certain chemical reactions.
Bonds vary in stability. Some are stable and form strong bonds that require a lot of energy to break apart. Others are weak and break with very little energy.
Atoms share electrons when they form covalent bonds.
The carbon atom can form four covalent bonds making it possible to make the many complex molecules found in living organisms.
Atoms with equal number of protons and neutrons are electrically neutral.
IONS, ACIDS AND BASES
Atoms can loose or gain electrons and become electrically charged in the process. These electrically charged atoms or molecules are called ions.
· Atoms that gain an electron become negative, 1- charge, and are called negative ions. We say this atom is reduced.
· Atoms that loose an electron become positive, 1+ charge, and are called positive ions.
We say this atom is oxidized.
Example: HCl can split into H+ and Cl-.
Here the hydrogen atom gave up one electron to the chlorine atom and became positive, which is 1+ or H+; the chlorine atom gained one electron and its negative charges went up by one. It is now 1- or Cl-.
Compounds that release hydrogen ions are called acids and those that combine readily with hydrogen ions are called bases.
The pH scale describes the number of free hydrogen ions in a solution.
· A pH of 7 is neutral; a pH less than 7 is acidic and above 7 is basic.
· The scale is logarithmic, which means that a pH6 represent ten times more hydrogen ions in solution than pH7.
Some ions like those of Na+ and Cl- can attract each other and form ionic bonds. These bonds could be very strong like those formed by sodium chloride, table salt.
Water molecules form hydrogen bonds. These bonds give water some of its important chemical and physical characteristics.
Substances that release hydrogen ions (H+) in water are called acids.
Substances that readily bond with hydrogen ions (H+) are called bases or alkaline substances.
The pH scale measures the concentration of hydrogen ions (protons) in a solution.
It is based on the negative logarithm of its concentration of H+.
Example: 10-6 concentration of H+ has a pH of 6; a concentration of 10-5 has a pH of 5, which is ten times stronger than pH 6.
Notice that the concentration of H+ increases as pH declines.
A pH of 10 has an acid concentration of 10-10 and a hydroxide concentration of 10-4. This is a basic or alkaline solution.
7 is neutral. Below 7 is acid and above 7 is basic or alkaline.
ORGANIC COMPOUNDS
Organic compounds are so named because they were thought to be produced only by living organisms.
Organic compounds contain carbon.
There are simple carbon compounds that are considered inorganic especially if they do not contain hydrogen, e.g. CO, CO2.
Carbon atoms form chains and rings that form different organic molecules found in the body of plants and animals. These are called biomolecules.
Lipids, proteins, carbohydrates and nucleic acids are the principal biomolecules.
· Lipids (fats and oils) are important components of cell membranes.
· Carbohydrates are sources of energy and also form part of supporting structures, e.g. cellulose forms the cell wall of plants.
· Proteins are involved in the structure and function of cells, e.g. structure of cell membrane; enzymes are proteins.
· Nucleic acids are very complex molecules. They store genetic information and direct the life processes.
CELLS
1. Cells are the basic unit of structure and function of all living things.
2. All cells come from preexisting cells.
All cells have a similar organization:
· semipermeable plasma membrane that surrounds the cell
· internal structures called organelles.
· DNA that contains the genetic material..
Organisms may be unicellular or multicellular.
A membrane, the plasma membrane, surrounds cells.
The plasma membrane is made of lipids, proteins and a few carbohydrates.
The plasma membrane regulates what enters and leaves the cell.
Inside the cells there are "organelles" that perform different functions and permit the cell to operate.
Enzymes are proteins that act as catalysts. These catalysts are specialized and permit life functions to take place.
Metabolism is the sum of all the enzymatic reactions taking place in the body of an organism.
ENERGY
Basic concepts
Energy is the capacity to do work.
· Energy is measured in joules. One joule can move one kilogram one meter.
· 1 kg = 2.2.pounds.
Work is any change in the state or motion of an object.
Energy can change form.
Kinetic energy is the energy of motion.
Potential energy is stored energy. It depends on the location and structure of matter.
· Chemical energy stored is food (e.g. sugars) is a form of potential energy.
Heat is the energy that can be transferred between objects of different temperature. It is the total amount of kinetic energy in a substance that its bulk is not moving.
Temperature is the measure of the energy of motion of molecules.
· A substance can have high heat content and low temperature!
· Low average molecular speed.
· Large mass with many moving molecules and atoms.
Thermodynamics
Thermodynamics regulates energy transfer.
Matter is recycled. It changes forms but it is neither created nor destroyed.
1. First law of thermodynamics.
· Energy of the universe is constant.
· Energy-mass cannot be created nor destroyed.
· Energy may be transformed, e.g. from a energy in a chemical bond to heat energy.
2. Second law of thermodynamics.
When energy is converted from one form to another, some of the usable energy is converted to heat and is dispersed in the surroundings.
At every step of energy transformation there is a loss of energy capable to do work.
No one process that requires energy conversion is 100% efficient.
All natural systems then to go from a state of order to toward a state of increasing disorder.
Entropy or amount of disorder increases reflecting the loss of energy.
There is less energy available at the end of a process than at the beginning.
APPLICATION TO ORGANISMS:
Organisms are highly organized both structurally and functionally.
Constant maintenance is required to keep this organization and a constant supply of energy is required to maintain these processes.
Energy is used by the cell to do work.
If the energy supply is depleted the cell will die.
ENERGY FOR LIFE
The sun is the ultimate source of energy for living organisms.
A few ecosystems are based on energy derived from inorganic substances and the earth molten interior.
Extremophiles
Extremophiles are organisms that live in severe conditions.
Deep-sea hydrothermal vents provide energy to an ecosystem that lives in total darkness and under tremendous pressure.
The energy source for this ecosystem is provided by inorganic molecules like hydrogen sulfide and hydrogen gas through a process called chemosynthesis.
Most of these extremophiles are single celled organisms called archaea.
Archaea are considered to be very primitive organisms and the conditions under which they live are thought to be similar to those in which life first evolved.
Green plants get energy from the sun
The sun produces warmth and light, both of which are needed for living organisms.
· Most organisms live within a narrow temperature range.
· Light is composed of particles of energy that travel as waves.
· Light is part of the electromagnetic spectrum, the entire range of electromagnetic radiation.
Of the solar radiation that reaches the earth’s surface, 45% is visible light, 45% is infrared radiation and 10% is ultraviolet radiation.
· 30% is reflected back into space.
· 20% is absorbed by the atmosphere.
· 50% is absorbed by ground, water and vegetation.
Less than 1% of the absorbed energy is used in photosynthesis. This small percentage is the energy base for all life on the biosphere.
HOW PHOTOSYNTHESIS CAPTURES ENERGY
Photosynthesis converts radiant energy into useful, high quality chemical energy in the bonds that hold together organic molecules (food!).
Photosynthesis can use mostly red and blue light. Green is reflected.
Every point of the earth is illuminated for six months of the year:
· Continuously during 6 months the polar summers.
· Alternating 12 hours of darkness with 12 hours light in the tropics.
Sunrays strike the earth obliquely in the higher latitudes.
Sunlight is responsible for the flow of wind, ocean currents, weather patterns and the hydrological cycle.
Photosynthesis is the conversion of light energy into chemical bond energy. It takes place in organelles called chloroplasts.
6CO2 + 6 H2O + solar energy ® C6H12O6 + 6O2
Chlorophyll molecules in the chloroplasts trap light energy and start a series of chemical reactions that begin the process of photosynthesis.
Photosynthesis begins with the split of water molecules, H2O, which releases oxygen into the atmosphere. This process happens only when light is present, from there comes the name light reactions of photosynthesis.
The light-dependent reactions make high-energy molecules of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate). These two types of molecules provide the energy for the next process, the light-independent reactions.
Another set of reactions occurs independently of light. These are called the light-independent reactions.
In these reactions, carbon dioxide is incorporated into small sugar molecules to make glucose, a high-energy sugar.
Cellular respiration releases chemical energy found in substances.
The energy released is used by the cell to make biomolecules, e.g. proteins, lipids, etc., and to do cellular work, e.g. movement.
C6H12O6 + 6O2 ® 6CO2 + 6 H2O + energy released
Photosynthesis captures energy; respiration releases energy.
LEVELS OF ORGANIZATION:
Atoms ® molecules ® macromolecules ® cells ® tissues ® organs ® organ systems ® organisms
FROM SPECIES TO ECOSYSTEMS
A population consists of all the members of a species living in a given area tat the same time.
An ecological or biological community is a system made of species populations living and interacting in the same area.
· Different species populations.
· In the same area.
· Interacting in spatial and trophic (feeding) relationships.
Characteristics of the community are species composition, diversity, stratification and food chains.
An ecosystem is a community of organisms and the physical environment interacting as a unit.
ENERGY TRANSFER: FOOD CHAINS, FOOD WEBS AND TROPHIC LEVELS
Photosynthesis is the base of the energy dynamics of an ecosystem, how organisms share food resources..
Biomass refers to the amount of biological material produced in an ecosystem.
The productivity of an ecosystem is measured by the amount of biomass produced.
· The primary productivity of an ecosystem is the biomass produced by photosynthesis.
· The secondary productivity of an ecosystem is the biomass produced by organisms that eat plants or other organisms.
Energy is passed from organisms that carry on photosynthesis (plants, algae, bacteria) to organisms that feed on them, and which in turn are eaten by other organisms thus forming a linked feeding series, a food chain.
Food chain refers to the sequence of organisms in a community on successive trophic levels and through which energy is transferred. It is a feeding series.
In a community there are many food chains
These chains interconnect to form a food web.
Food webs are usually very complex involving hundreds of species.
Trophic level is the position of an organism in the food chain.
Producers or autotrophs make food from simple organic matter.
· The largest group in a community.
Consumers or heterotrophs obtain their food by eating other organisms.
· Primary consumers or herbivores eat plants.
· Secondary and tertiary consumers or carnivores eat other animals.
· Omnivores eat both plant and animal materials.
· Parasites, scavengers, detritivores and decomposers feed at all levels.
· Decomposers or saprobes feed on dead organisms and wastes.
Material available to saprobes include:
· Dead animals (carrion): scavengers.
· Feces and excreted organic compounds (detritus): detritivores.
· Dead plants: logs, stumps, fallen leaves, dead roots: detritivores.
· Overripe fruit.
Fragments of these materials form detritus.