Download - Characteristic of life
6 Characteristics of Living Things
• Made up of cells
• Reproduce (sexually or asexually)
• Have DNA (genetic code)
• Grow and develop
• Metabolism -Use materials and energy
• Respond to stimuli
Cont.
• Homeostasis – maintain a stable internal environment
• All living things are carbon based – organic compounds
• Carbon is the most diverse element and can form millions of compounds
• Macromolecules-giant molecules formed from monomers (smaller molecules) that form polymers (larger molecules)
Four groups of Organic Compounds
• Carbohydrates – (carbon-hydrogen-oxygen) in a 1:2:1 ratio (C6H12O6)
• Carbohydrates are the main source of energy for living things
• Carbohydrates are sugars that break down for immediate energy and the balance is stored as starch (monomer is sugar, polymer is starch)
Cont.
• Lipids – mostly carbon and hydrogen• Common lipids are fats (solid), oils (liquid) and waxes• Lipids are made of glycerol and fatty acid molecule chains
• The molecule chain determines saturated (solids) or unsaturated fats
Cont.
• Nucleic acids – contain hydrogen, oxygen, nitrogen, carbon, phosphorus
• Formed from monomers called nucleotides: 3 parts– 5-carbon sugar– Phosphate group– Nitrogenous base
• Sugar, base, phosphate group
Cont.
Cont.
• Nucleic acids store and transmit genetic information (the blue print of life)
• DNA-deoxyribonucleic acid (contains sugar group deoxyribose)
• RNA-ribonucleic acid (contains sugar group ribose)
Cont.
• Proteins-macromolecules made of nitrogen, carbon, hydrogen, oxygen
• Polymers of molecules called amino acids (monomers)
• Contain an amino groups (NH2-) and a carboxyl group (-COOH) at each end with an R-group in the middle
• The R-group determines the amino acids
Cont.
• Some acidic some are basic
• Instructions for arranging amino acids into different proteins is stored in DNA
• Each protein has a specific role in an organism
Chemistry of Life
• All living things are constantly undergoing chemical reactions
• Reactions always involve the breaking and making of new bonds
• All reactions involve a reactant and a product
• CO2 + H2O → H2CO3 (CO2 is taken up)
• H2CO3 → CO2 + H2O (CO2 is released)
Cont.• Some reactions release energy
(exothermic) (spontaneously)• Some absorb energy (endothermic)
(requires energy to complete)• Importance of this: all living things must
have a source of energy to allow for chemical reactions to take place(metabolism)
• Activation energy-minimum energy need to start a reaction
Enzymes
• Catalyst-speeds up a reaction
• In living things, some reactions are very slow or require extreme energy to happen, catalyst work to lower the activation energy need for the reaction
• Enzymes are proteins that act as biological catalysts
Cont.• CO2 + H2O → H2CO3 (carbonic acid)
• Very slow reaction that by itself would allow CO2 to build up in bloodstream
• Bloodstream contains an enzyme called carbonic anhydrase that speeds the reaction by a factor of 10 million
• Enzymes are very specific only catalyzing one type of reaction (in name of enzyme that catalyzes a specific reaction)
Viruses
• Viruses are not living organisms, do not contain all of the 6 requirements of living things (cannot reproduce)
• Contain a core DNA or RNA surrounded by a protein coat (capsid)
• Highly specific to a particular type of cell• Plant virus infects plants, bacteria virus
infects bacteria and animal virus infects animal
Cont.
• 4 shapes of virus: spacecraft, spheres, crystals, cylinders
• Lytic infection – virus enters cell, makes copies of self, and cell bursts spreading the virus
• Lysogenic infection – virus integrates DNA into the host DNA and viral genetic material replicates along with host cell’s DNA
Cont.
• Viruses can lay dormant for many generations, however, it will eventually become active
• Retrovirus – produce a DNA copy of their RNA (backward)
• AIDS is a retrovirus• Viruses were not the first living organisms,
however, have been around for billions of years
Bacteria
• Prokaryotes – single-celled organisms lacking a nucleus (commonly referred to as bacteria)
• Monera divided into eubacteria and archaebacteria
• Identified by shape, chemical nature of cell walls, movement and how they obtain energy
Shapes
• bacilli – rod shaped• Cocci – spherical• Spirilla – spiral• Bacteria can be heterotrophs or autotrophs• Reproduction:• Binary fission (divides in half)• Conjugation – genetic material is exchange by
way of “bridge” between two cells• Spore formation – structure of stored genetic
material which will germinate when conditions are right
Importance of bacteria
• Necessary to maintaining life:
• Nitrogen fixation – converting nitrogen into usable material (plants)
• Humans – contain trillions of bacteria good and bad (outnumber cells 10:1) most found in intestines; digestion, removal of waste
Germ Theory
• Disease – produced by agents: bacteria, viruses, fungi – environmental, genetic
• Pathogen – any disease causing agent
• Late 1800’s Louis Pasteur and Robert Koch theorized that diseases were caused by germs
Koch’s Postulate
• 1. pathogen should always be found in the body of a sick organism and not in healthy organism
• 2. pathogen must be isolated and grown in controlled environment (lab) in pure culture
• 3. when cultured pathogens are place in new host, should cause the same disease as the original host
• 4. injected pathogen should be isolated from second host and should be identical to the original pathogen
Agents of disease
• Virus – flu, polio, HIV, smallpox, warts
Bacteria – anthrax, streptococcus, botulism, diphtheria
Protists – malaria, typanosoma (African sleeping sickness), dysentery
Worms – tapeworm, hook worm,
Spread
• Physical contact (STD) or by indirect contact (sneeze)
• Food or water – contaminated source (cholera)
• Infected animals – vectors (carrier), rabies, Lyme disease, West Nile
• pigs, cows, birds
Prevention and treatment
• Vaccinations – MMR, polio, flu
• Antibotics – kill bacteria but don’t damage cells: – penicillin (accident), Cipro, vancomycin – do not effect viruses
• Antivirals – inhibit the ability of viruses to invade cells and multiply