biol 171 lec 1

Elements of Life

• Carbon (C) makes up 18.5% of the weight of most cells
• Oxygen (O) makes up 65.0% of the weight of most cells
• Four elements (C, O, H, and Ca) make up about 96% of the weight of most cells
• The remaining 25 essential elements are needed in smaller amounts
• Trace elements make up less than 0.01% of the weight of most cells

Atomic Structure

• Electrons are organized in electron shells
• The outer electron shell is the most important
• A full outer electron shell means a stable atom
• The number of electrons in the outer electron shell determines how an atom will interact with other atoms

Chemical Bonds

• Atoms lose, gain, or share electrons to fill their outermost electron shell
• Atoms react with other atoms to form molecules
• Ionic bonds: oppositely charged ions attract
• Covalent bonds: two atoms share one or more electrons

Ionic Bonds

• Ion: an atom with an electrical charge due to gain or loss of electron(s)
• Sodium atom (Na) loses an electron to become a sodium ion (Na+)
• Chlorine atom (Cl) gains an electron to become a chloride ion (Cl-)

Covalent Bonds

• Covalent bonds: the strongest bond
• Electrons are not always shared equally
• Atoms joined into a molecule via covalent bonds
• Electronegativity: an atom's ability to attract electrons
• Electronegativity increases from left to right in a row in the periodic table

Water Molecule

• Water molecule (H2O): a very important polar molecule
• Hydrogen bonds: weak electrical attraction between neighboring water molecules
• Hydrogen bonds give water unique properties

Origin of Life

• Macromolecules: large molecules found in all living creatures
• Organic molecules: carbon-based molecules
• Carbon is the most important element for life
• Carbon skeletons vary in length and may have double bonds or be arranged in rings

Molecules of Life

• Macromolecules include: carbohydrates, lipids, proteins, and nucleic acid
• Most macromolecules have a unique monomer
• Monomers are linked together through covalent bonds to produce a polymer via dehydration reactions

Connective Tissue Cells

• Connective tissue cells are specialized to connect, anchor, and support the structures of the body
• Types of connective tissues include: loose connective, dense connective, blood, bone, cartilage, and adipose

Extracellular Matrix (ECM)

• ECM consists of a mixture of proteins, polysaccharides, and in some cases, minerals
• The matrix serves two general functions: provides a scaffold for cellular attachments and transmits information to the cells to help regulate their activity

Organs and Organ Systems

• Organs are composed of multiple tissue types
• Organ systems contain multiple organs that work together
• There are 11 different organ systems in the human body

Test your understanding of fundamental biology concepts, including the elements of life, homeostasis, and evolution.