Introduction to 5a: The Chemical Context of Life

We know that Life is organized at many levels; BUT what levels does this class focus on?

Cells, Organelles, Molecules, and Atoms

Go more into detail about these elements of life: Cells, Organelles, Molecules, and ATOMS; like what are good analogies and ways to think about it (LEGO ANALOGY)

Atoms: Individual Lego Pieces

- these are your Carbon, Hydrogen, Oxygen, and Nitrogen

Molecules: Atoms joined together

- When 2 or more atoms bond; a molecule is formed

• - Ex: Water (H2O)= hydrogen and oxygen atoms

• - Glucose, DNA, Proteins, and Lipids are important molecules in biology

Organelles: Specialized Structures Inside Cells

• - Mitochondria

• - Ribosomes

• - Nucleus

• - Lysosomes

Cell: Basic structural Unit of Life; This is like a big city with everything else in between

• - Consists of molecules and organelles

• - Genetic Info

• - Systems that allow it to maintain itself

The Book Micrographia by Thomas Hooke (1965) is important because?

• - Coined the term “cell” after obeserving the wall like tissue of cork plant tissue

• - First Illustration of plants and animals through microscopes

Why did Hook or people in general believe that only plants had cells?

Ppl (another microbiologist Leeuwenhoek) had:

• - Observed Bacteria in bond water and spit but found no cells despite higher resolution

• - Also from Hooks Cork observation; they had found the cell wall; which animals do not have; hence yk they thought only plants have cells

How might we define what cell theory means?

Basic set of rules scientists use to define what cells mean for life

3 parts to cell theory?

1. All Living Organisms are composed of one or more cells

• Cell is the smallest level of organization that can carry out the processes necessary for life

  • It’s because of cells that you have a system to live: (like use energy, reproduce, grow, respond, etc)

2. The Cell is the most basic Unit of Life

• Even atoms and molecules aren’t living

• They are typically deemed underneath cells like in terms of levels

3. All Cells come from pre-existing cells

• Makes sense because as discussed before cells are the most basic unit of life; so ofc u need cells to make more cells

• Cells divide; thats how they reproduce and stuff

• Even for a unicelluluar organism; once it divides they are now officially 2 organisms; whereas for like humans for example; there needs to be combination for 2 types of cells

What did Dutrochet say about: All living things are made up of cells?

• He stated that growth results from both the increase in the volume of cells and the addition of new little cells

  • Cells get bigger by making its own stuff; hence volume increases

    • more proteins, more cytoplasm, more DNA, etc

    • Ig thats why they say to eat more to grow because well food consists of stuff

  • Also adding more cells in an organism ofc means yk the organism will expand; hence growth; like u need more room to place those cells

    • to an extent; the cells need to get big to a certain size in order to yk become big; so these are connected steps

• He also stated that chlorophyll was necessary for photosynthesis

  • Chlorophyll is located inside a plant cell

Modern Additions of Cell Theory

• Energy Flow occurs in cells

  • Cells store and use chemical energy for metabolism

  • Makes sense because well Cells need energy in order to carry out its processes

  • Hence it flows from food—-cell and then from cell——body

• Genetic Information is Passed From Cell to Cell

  • Genes that determine the characteristics of a cell or species from one generation to the next

    • The cell first replicates (copy and pastes) it’s DNA; and then the cell divides

• All cells have the same basic chemical composition

  • Macromolecules that make up cells consist of the same elements and have the same structure among all life forms

    • Macromolecules are: Carbs, Lipids, Proteins, Nucleic Acids

  • TLDR: All cells across all life have these macromolecules and same basic structure

All matter is composed of what? And define that

Elements

Substances that cannot be broken down into other substances by chemical reactions

(basically the fundamental unit)

What are the 4 Elements that are extremely important to life? (They make up roughly 96% of mass)

Oxygen, Carbon, Hydrogen, and Nitrogen

Oh Caran Hell Nah

Living organisms are mostly made up of what; and how many elements?

11: Oxygen, Carbon, Hydrogen, Nitrogen, Calcium, Phosphorous, Potassium, Sulfur, Sodium, Chlorine, Magenisum

The Rest are trace elements: which are <0.01% of mass

Given the makeup of the human body, what compound accounts for the high percentage of oxygen?

Water (H2O)

The smallest unit of an element is what?

Atoms

What is the nucleus of an element made up of?

Protons and Nucleus

Remember the electrons are surrounding nucleus

Most of an atom’s mass comes from?

its nucleus

Inside an atom there is??? (hint: the basic 3)

protons, electrons, and neutrons

The Number of protons in an atom is called what? And what does this dictate?

Called: Atomic Number

Dictates the chemical properties of an atom

What does the 23 stand for? What does the 11 stand for?

23: Mass Number = # of protons + neutrons

11: Atomic Number = # of protons

Atomic Number corresponds with exactly to the element’s position on PT

How do you find #of electrons?

In a netural atom:

#protons = #electrons

Remember protons are a (+ charge) and electrons are a (- charge)

Hence makes sense in a neutral atom why protons = electrons; cuz yk they cancel out

BUT in a non-neutral atom:

the balance of protons and electrons determines the charge in an atom

so if its like

(na)^-; then there is one more electron than proton

What unit is used to measure atomic mass?

Daltons (Da) which is interchangeable with atomic mass

Mass in Daltons = protons and neutrons; which is basically equivalent to mass number

this is js because electrons are way to tiny and the math just ends up working out

Also remember: 23 daltons = 23g/mol; js the math explained in terms of yk math

What is an isotope?

An Isotope of an element; is still the same element just with a different number of neutrons

How do you find neutrons in an element?

Top number - Bottom number

Top = protons + neutrons

Bottom = protons

so yk cancels

12 neutrons

What are unstable isotopes?

The nucleus’s proton-neutron ratio is thrown off from what that specific element’s ideality is. (either having too many neutrons or too little neutrons). Therefore the nucleus isn’t sitting in the lowest state of energy and has extra energy. It doesn’t hold on to that extra energy and so it spits out to become more stable (this may even result in a change of element); which results in radioactive decay

Different elements have different tolerencces

Some are fine with slight change of proton: neutron ratio and can still be considered stable; some are more sensitive

Where are electrons found?

Found in electron shells

These shells are like rings at increasing distances from the nucleus

• First Shell: closest to the nucleus = lowest energy level

• Second Shell: further out = higher energy

• Third Shell: furthest down = highest energy level

The Farther a shell is from its nucleus, the more energy an electron has sitting there

The Nucleus is essentially pulling the electrons inward (pos attracts neg)'; and electrons out in shell 3 is basically fighting against that pull more; so it takes more energy for it to sit that far out

Hence: it takes more energy for an electron to go from an inner to outer level; thus electron has more energy when it goes outer

Likewise; it takes less energy for an electron to from outer to inner

Elements combine to make….

Compounds

What is radioactive decay? And what typically undergoes it?

Radioactive Decay: Essentially when something (typically isotopes in this concept) slowly break down over time into something more stable

What is happening here?

This is showing the unstable isotope undergoing radioactive decay

• Neutron changes into a proton

• An Electron is being released

• An Antineutrino is released

Basically this happening remember nature always wants to be in its most stable form

To this; it releases electrons; and becomes Nitrogen (by taking extra neutron and turning it into a proton)

Check doc for more detailed theory

What is half-life?

The amount of time it takes for half of a radioactive substance to decay into (break down into something else) (usually into smth more stable)

• This is usually unstable isotopes

• Isotopes decay at a constant rate

Uses for isotopes in reasearch and med

rlly simple js go over how researchers would use this

isotopes: atoms with a built-in tag so basically u can see how much it takes for the isotope thingy to change (radioactive) and can track that way

What does half-life describe? Does a longer half-life means stability is more or less?

Stability

Cuz think; half life is telling us the time it takes for ½ the substance to go away

• Longer half-life means the isotope is stable; because think abt its not in a rush to change and its fine with being how it is longer

• Shorter half-life means the isotope isnt stable; because think abt its in a rush to change and changes easily

Where are electrons found? (go in detail; valence, orbital)

Electrons are found in electron shells.

Valence shell: the outermost electron shell that contains electrons

Orbital: a place where an electron is very likely to be found; REMEMBER this doesn’t mean electrons will be there but typically u can find them here

Think of an electron shell like a hotel; and the floors/levels in a hotel (1st, 2nd, 3rd); and the rooms on each floor; orbitals are like the rooms are on the floor; u may or may not find people in the room at a specific given time; but thats definitely where ppl live

Why does it make sense that # of electrons in valence shell determine reactivity?

1. They are on the outer shell so they can react and connect with other atoms and participate in a chemical reaction 

2. They also are at an higher energy than other electrons in the other shells; so in a way they also have more energy to partake in a chemical reaction

What is chemical bonding essentially

• Atoms can share or transfer electrons in their valence shells to form a chemical bond

What is a covalent bond?

Sharing of electrons

Either:

• Polar: the electrons are shared equally

• Nonpolar: the electrons are shared unequally

Examples: H2, O2, H2O, CH4

What is a ionic bond?

Transfer of electrons

Nacl, NaF, Kcl

What is a hydrogen bond?

• Hydrogen Bond: forms between a Hydrogen bonded to an electronegative atom (N or O or F)

• Remember FON

• This is through electrostatic attraction

How are bases in DNA connected?

Through Hydrogen Bonds!!!

What are van der waals interactions?

“transient regions of polarity that become attractive, and induce polarity in neighboring molecules”

• things like LDFs, Dipole-Dipole, Dipole induced dipole

• Typically LDFS are js when electrons in a nonpolar molecule become temporarily polarized and then influence a nonpolar molecule and form bond

• Dipole -Dipole: btwn 2 semi permanente

• Dipole induced dipole: a polarized molecule influences non-polarized molecule

What are the 2 weak bonds in chemistry?

Hydrogen Bonds

Van Der Waals