Lecture 1 and Lecture 2 (Textbook based)

Element

A substance that cannot be chemically broken down into other substances

Atom

Smallest unit of an element that retains its properties

• AKA the smallest bit of matter that can be subdivided without loosing its essential properties

Subatomic particles

Protons (+ charge, mass ≈1), neutrons (neutral, mass ≈1), electrons (− charge, negligible mass)

Atomic number

Number of protons in an atom’s nucleus, determines the element’s identity

Atomic mass

Approximate sum of protons and neutrons in an atom

• Protons and neutrons have the same mass

• Electrons are so light => we ignore their weight

Electron behavior

Electrons are attracted to protons in the nucleus but repelled by each other

rapid movement keeps them from collapsing into the nucleus

Isotopes

Atoms of the same element where the number of protons does not equal the number of neutrons

• DONT have charges because neutrons have no charge

• have different atomic masses compared to the original atom

Radioactive

Atoms with unstable nucleus that decomposes/breaks down and releases high speed particles with a lot of energy

• When elements loose proton (+) particles they become entirely new elements

Applications of radioactivity

Used in dating fossils, cancer treatment, and medical imaging

Risks of radioactivity

High-energy emissions can damage DNA and cells

Periodic table

Organizes elements by atomic number and recurring chemical properties

about 94 naturally occurring, ~28 synthetic

Big Four elements in the human body

Oxygen, carbon, hydrogen, nitrogen—together >96% of human body mass

Other important elements in the body

Calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium

Trace elements

Required in very small amounts but critical for survival (e.g., iron, iodine, zinc)

Molecule

Two or more atoms held together by bonds

• It takes energy to break these bonds (called bond energy)

Chemical reaction

Process where reactants are transformed into products by forming or breaking bonds

• essential to all processes of life

  • if a reaction results in a lower bond energy than what we started with it means excess energy was released to be used in life processes

Bond energy

Energy required to break a bond

if products have lower bond energy than reactants, excess energy is released

Valence electrons

Electrons in the outermost shell that determine bonding capacity

Covalent bond

A bond formed by sharing one or more pairs of electrons between atoms

• when an atom, like Hydrogen, needs to complete its electron shell it will covalent bond with another Hydrogen to form H2

Single covalent bond

Sharing of one pair of electrons (e.g., H2 molecule)

Double covalent bond

Sharing of two pairs of electrons (e.g., O2 molecule)

• 4 electrons shared in total

Carbon bonding

Carbon has four valence electrons, allowing it to form four covalent bonds, enabling diverse structures

Ionic bond

A bond formed when electrons are transferred from one atom to another, producing oppositely charged ions that attract and form an ionic compound

• electrons circle around a nucleus instead of being shared by both nuclei (as in covalent bonds)

Ions

Atoms where the number of protons is not equal to the number of electrons

• cation = positive (lost e−)

• anion = negative (gained e−)

Example of ionic bond

NaCl forms when sodium donates an electron to chlorine, producing Na+ and Cl−

Hydrogen bond

Weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative atom (O or N) in another molecule

• Bonding is from (+) or (-) charges but does NOT involve ions

  • This is because a hydrogen molecule is polar and has a (+) and (-) region

Polarity

Unequal sharing of electrons in polar covalent bonds produces partial charges that enable hydrogen bonding

Importance of hydrogen bonds

Though weak individually, large numbers of them give water and biomolecules critical properties

Why are there unique properties of water?

Result from polarity and hydrogen bonding

Property 1: Cohesion

Water molecules stick together due to hydrogen bonding

• critical for transport in plants

• Causes surface tension

Property 2: High heat capacity

Water absorbs large amounts of heat before temperature rises/changes

• Maintain consistent body temperature for humans

• due to hydrogen bonds

Property 3: Low density as ice

Water is less dense as it cools down (unlike most substances) because of hydrogen bonding

• When temperature (which measures the movement of molecules) drops, water forms a lattice that takes up a lot more space compared to liquid water

• Ice is less dense than water

• Lakes/Oceans freeze from the top down, protecting the fish

Property 4: Good solvent

Water dissolves polar and ionic substances, enabling biochemical reactions and the ability to easily transport substances through cells, organs, and plants

• Because water is polar it can pry apart molecules

  • Water can not pry apart nonpolar things like oil

Surface tension

Enhanced cohesion at water’s surface resists disruption (allows some organisms to “walk” on water)

• Tension because hydrogen at the top of water has fewer things to bond to => is strong and allows for things to float on the surface

• Hot water has less surface tension and is better to penetrate in cleaning

Capillary action

Water’s adhesion to surfaces and cohesion with itself allows it to move upward through narrow spaces (e.g., plant xylem)

Hydrogen bonding and temperature

Heat input breaks hydrogen bonds, slowing temperature increase compared to other liquids

Nonpolar exclusion

Nonpolar molecules (oils, fats) do not dissolve in water

they aggregate instead

Science

An intellectual activity that involves observing, describing, and experimenting to understand natural phenomena and the world

Science as a pathway

Science is not just a list of facts but a process for discovering and better understanding the world

Central question of science / science thinking

“How do you know that is true?”

Example of scientific skepticism

Kellogg’s claim that fortified cereals improved children’s immunity was challenged, tested, and disproven

Biological literacy

A general, evidence-based understanding of biology and science that enables people to make informed decisions

• use scientific inquiry on a real world biological issue

• communicate these ideas to others

• integrate the ideas into your decision making

Benefits of biological literacy

Helps individuals evaluate claims, make personal health decisions, and engage with social, political, and legal issues involving science

Consequences of lacking biological literacy

Individuals may be misled by experts or false claims for personal or corporate gain

How can we define life (Characteristics of life)

Cellular structure, metabolism, sensitivity and responsiveness, homeostasis, growth and reproduction, evolutionary adaptation

Cellular structure

All living organisms have complex, ordered organization of one or more cells that carry out life functions

Metabolism

Ability to acquire, use, and transform energy to perform work

Responsiveness

Living organisms respond and adapt to environmental stimuli

Homeostasis

Ability to maintain relatively constant internal conditions despite external changes

Growth, development, and reproduction

Living things grow, change, and produce offspring

Evolutionary adaptation

Populations change traits over time, leading to…

• adaptations that increase survival and reproduction

• more diverse organisms

Borderline cases of life

Entities like viruses and computer programs challenge strict definitions of life

Themes in biology

Five central ideas unify biology: evolution, structure and function, information flow, energy and matter pathways, and systems

Structure and function

Physical features of organisms are closely linked to their roles and functions

Information flow, exchange, and storage

Genetic information carries instructions for traits, passed to offspring, influencing growth and function of life

Pathways of energy and matter

Organisms transform matter and use energy through chemical reactions for growth, movement, and reproduction

Systems

Life is organized at multiple levels:

• molecules, cells, tissues, organs, organisms

• populations, communities, ecosystems, biosphere

Biodiversity

Variety of genes, species, and ecosystems on earth

Value of biodiversity

Biodiversity has intrinsic (inherent worth) and extrinsic (human-use) value

Examples of biodiversity’s extrinsic value

Taxol from Pacific yew treats cancers

Toxin production in nature

Often evolves as protection against predators but can be co-opted for human medicine

Ecosystem services (what are the 4 values biodiversity has to us?)

provisioning, regulating, habitat, cultural

Provisioning services

Direct products humans obtain from ecosystems (food, medicine, raw materials)

Regulating services

Benefits ecosystems provide by regulating natural processes (climate regulation, water purification)

Habitat services

Biodiversity provides living spaces and maintains genetic diversity

Cultural services

Non-material benefits such as recreation, spiritual value, and aesthetic inspiration

What are the levels of biodiversity

Biodiversity occurs at multiple levels: # of

• ecosystems

• species

• genes and alleles

Species richness

Most common way to measure biodiversity, by counting the number of distinct species in an area

Conservation biology

Interdisciplinary field focused on understanding and preserving biological resources and biodiversity

Challenge of conservation biology

Biodiversity has many types of value, making it difficult to balance competing human interests

Nucleus of an atom

• center of atom

• made up of proton and neutron particles

Protons

(+) electrical charge

Neutrons

No electrical charge

Electrons

(-) electrical charge

• Orbits the nucleus

• Electrons repel other electrons

• Attracted to (+) protons

What elements are in the atmosphere

nitrogen, oxygen, argon, CO2

Ionic compound

Where ions of two or more elements are linked by an ionic bond

• They are neutral because its between a (+) ion and a (-) ion

Polar molecules

A molecule made up of polar covalent bonds with an unequal distribution of charges in different parts of the molecule

• one region is (+) another region is (-)

• Ex) In a molecule with hydrogen, the electron orbits around the other atom in the molecule (since it is always more attractive compared to Hydrogen’s 1 proton) the result is a polar molecule with a (+) and (-) region…perfect for a hydrogen bond

Biology

The study of living things through a scientific approach (aka biological literacy)