Chapter 1
All organisms can be categorized
based on certain characteristics into
one of three domains, then six
kingdoms
There is some debate about this
among scientists, so you may find
different answers, e.g. some include a
seventh kingdom.
1.2 Prokaryotes and Eukaryotes
•Prokaryotic organisms (pro:before)
• Kingdoms: Archaea and Eubacteria
• All unicellular (one cell per organism).
• no membrane-bound organelles.
• DNA is located in the cytoplasm.
• Sometimes called “primitive”
•Eukaryotic organisms (eu: good or well)
•Kingdoms: Protists, Fungi, Plants and Animals.
•Membrane-bound organelles, DNA in nucleus,
more complex, also contain ribosomes.
some are unicellular
Archaebacteria
•Single-celled
•Prokaryotic
•Primitive
•Live in extreme environments
very high temperatures
very low temperatures
highly saline environments
highly acidic environments
•Look at definition of thermophiles, halophiles, methanogens
Archaea
1.2 Organization of Living Things
Eubacteria
•Generally single-celled (some may be in groups)
•Prokaryotic
•Found almost everywhere on Earth
•Most are harmless or helpful
•Some can cause human diseases. Examples: tetanus, syphilis, pneumonia, tuberculosis
Bacteria
In the Human Gastro-Intestinal Tract: ~500 species and trillions of bacterial cells
The difference between Archaebacteria and Eubacteria lies mainly in their ancestral cell lineage. (i.e. they have an independent evolutionary history)
Other key differences include:
•the types of environments that they live in
•biochemical variations in cell components
1.2 Organization of Living Things
Protists
•Single-celled
•Eukaryotic
•Various species have characteristics similar to:
Fungi (spores)
Plants (chloroplastsphotosynthetic)
Animals (locomotion)
•May be photosynthetic
•May have structures such as flagella or cilia.
Eukarya
Protists associated with human disease: Plasmodium causes malaria;
Giardia causes severe diarrhea (beaver fever)
1.2 Organization of Living Things
Fungi
•Multicellular (except for yeast)
•Eukaryotic
•Non-photosynthetic
•Some are beneficial and some are poisonous to humans.
•Examples include mushrooms, mold, and mildew.
Plants
•Multicellular
•Eukaryotic
•Photosynthetic
•May live on land or in water
Animals
•Multicellular
•Eukaryotic
•Non-photosynthetic
•Can live on land or in water
•Have locomotion
All living things include the elements: carbon, oxygen, hydrogen, and nitrogen (C O H N).
•These elements form molecules such as sugars, amino acids, fatty acids, and nucleotides.
•Small molecules combine into various macromolecules: polysaccharides (complex carbohydrates), proteins, fats, and nucleic acids.
•Note: there are many other elements that go into making different components of macromolecules.
All living things are composed of one or more cells.
•All cells have a membrane that separates the inside of the cell from the outside of the cell.
•Some organisms are single celled, such as bacteria, yeast, or some algae.
•Some organisms are multicellular, such as zebra muscles, trees, and cobra chickens (Canada geese).
All living things use energy for metabolism, growth, movement, etc.
•Most energy on our planet comes from the sun.
•The sun’s energy is captured by photosynthetic organisms, that are consumed by other organisms (herbivores, omnivores). Carnivores eat other animals for energy.
•Metabolism is the transfer of energy from one form to another: for example, our muscles converting glucose into ATP for movement, growth, etc.
All organisms reproduce.
•Reproduction can be just cellular, e.g. body cells reproducing.
•Some organisms reproduce every 20 minutes (bacteria), some reproduce every 6 weeks (mice), and some reproduce only a few times in their lifetimes (humans).
•Different ways to reproduce: binary fission (copies of DNA) and sexual reproduction (intermixing of DNA).
All living organisms have genetic material: DNA
(some viruses, e.g. SARS COV-2, use RNA, but they’re not considered “living”)
•The DNA in all organisms must divide before the organism itself can divide. (Chapter 8, next semester)
•DNA contains genes that partially determine an organism’s characteristics. But the environment can also affect characteristics.
•All populations of organisms continuously change genetically from one generation to the next. This depends on occasional mutations.
•Humans have 46 chromosomes, but the versions of genes on those chromosomes vary, such as the genes that encode for skin pigmentation or body height.
Every organism must maintain a stable internal environment.
•e.g. humans must maintain consistent blood pH, blood sugar levels, and body temperature, regardless of the food we eat or the weather.
•To maintain homeostasis, organisms use positive and negative feedback mechanisms.
Homeostasis depends on receptors to detect changes in the internal environment:
•Chemoreceptors detect chemical concentrations, such as of neurotransmitters, drugs, or hormones.
•Osmoreceptors detect changes in osmolarity; i.e. water and ion concentrations.
•Tactile receptors detect touch, pressure, and vibration.
•Baroreceptors detect blood pressure.
•Photoreceptors detect light (the retina in humans).
•Mechanoreceptors detect stretching (e.g., spindle fibres in muscles).
•Proprioceptors detect body position.
•Nociceptors detect pain.
•Thermoreceptors detect temperature
•All living things contain water.
•Infants: about 75% water, which decreases with age (mostly in the first 10 years of life but continues into old age)
•Healthy adult males: about 60% water
•Healthy adult females: about 55% water (and usually have more body fat than men)
•Obese people: can have as little as 45% water
The water in your body is divided into two compartments:
1.Intracellular: inside your cells. This is where most of your body’s water is found.
2.Extracellular: outside your cells
•Interstitial fluid: between your cells
•Blood plasma: non-cellular part, made of proteins, ions and mostly water
Oxygen pulls the hydrogen’s electrons closer, so that end has a slight negative charge. The H ends have a slight positive charge.
•Polar molecules have a slight charge on opposite ends. e.g.) water, sugars, amnio acids. They are neutral overall.
•Polar molecules are hydrophilic (water-loving).
•Non-polar molecules are hydrophobic (water-hating
Since a single water molecule has both positive and negative ends:
•Many water molecules together will attract each other’s oppositely-charged ends and form hydrogen bonds.
•This causes surface tension.
Hydrogen bonds are very weak, but biologically very important
•All living things are based on carbon atoms and make organic molecules.
•The four primary atoms that make up all living things:
•Carbon, oxygen, hydrogen and nitrogen
COHN
The building materials of the body are known as macromolecules because they can be very large.
•There are four types of macromolecules.
•Proteins
•Nucleic acids
•Carbohydrates (not just sugar!)
•Lipids/fats
•You are probably familiar with foods that contain a lot of each of these.
Large macromolecules are assembled from many similar small components called monomers (building blocks).
•Many similar monomers covalently bound together form a polymer.
• All biological polymers are assembled by dehydration synthesis.
A covalent bond is formed by removing a hydroxyl group (OH) from one subunit and a hydrogen (H) from another subunit.
•This process of linking together two subunits to form a polymer is called dehydration synthesis because this amounts to the removal of a molecule of water (H2O).
•Dehydration synthesis requires an enzyme to complete the chemical reaction.
Breaking polymers into their monomers (disassembling) is the reverse of dehydration synthesis.
•A molecule of water is added to break the covalent bond between the monomers.
•This process is known as hydrolysis (water-breaking) and usually requires an enzyme.