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Bio 101 Chapter 2 in Class Notes, Lecture notes of Biology

Mercer County Community CollegeBiology

Class notes for chapter 2 - chemical context of life. Provides all information that will be on test 1 from this chapter.

Typology: Lecture notes

2022/2023

Available from 01/14/2023

CinderIsStudying
CinderIsStudying 🇺🇸

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Bio 101 Chaper 2 – Chemical Context of Life
A Chemical Connection to Biology
Living organisms are subject to basic laws of physics + chemistry
Matter, Elements, and Compounds
Organisms are composed of matter – anything that takes up space + have mass
Element – substance cannot be broken down to other substances by chemical reactions
Compound – two or more elements in a fixed ratio
Essential elements of life
oTrace elements – required by an organism in minute amounts
Element’s Properties Depend on Atomic Structure
Elements consist of unique atoms
Atoms are composed of subatomic particles
oNeutrons – no charge
oProtons – positive charge (+)
oElectrons – negative charge (-)
Neutrons + protons form the atomic nucleus
Electrons form a cloud around nucleus
Atomic Number + Atomic Mass
Atomic number – number of protons in nucleus (subscript left)
Element’s mass – sum of protons + neutrons in nucleus (superscript right)
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Bio 101 Chaper 2 – Chemical Context of Life A Chemical Connection to Biology  Living organisms are subject to basic laws of physics + chemistry Matter, Elements, and Compounds  Organisms are composed of matter – anything that takes up space + have mass  Element – substance cannot be broken down to other substances by chemical reactions  Compound – two or more elements in a fixed ratio  Essential elements of life o Trace elements – required by an organism in minute amounts Element’s Properties Depend on Atomic Structure  Elements consist of unique atoms  Atoms are composed of subatomic particles o Neutrons – no charge o Protons – positive charge (+) o Electrons – negative charge (-)  Neutrons + protons form the atomic nucleus  Electrons form a cloud around nucleus Atomic Number + Atomic Mass  Atomic number – number of protons in nucleus (subscript left)  Element’s mass – sum of protons + neutrons in nucleus (superscript right)

 Ex. Mass Number C Atomic number  Ex. 12 C ★(test question) 6 o How many protons? – 6 o How many neutrons? – 6 o How many electrons? – 6 Isotopes  All atoms of an element have the same number of protons but may differ in the number of neutrons  Isotopes – two atoms of an element that differ in number of neutrons  Radioactive isotopes – nucleus decays spontaneously, giving off particles + energy Electron Distribution + Chemical Properties  Chemical behavior is based on distribution of electrons (e-) in the electron shell  Valence electrons – electrons in the outermost shell (valence shell)  Chemical behavior mostly determined by valence electrons  Elements w/ full valence shell are chemically inert  Valence number – number of electrons needed to complete outer shell by adding or losing electrons Formation + Function of Molecules Depend on Chemical Bonding Between Atoms  Atoms w/ an incomplete valence shell can share or transfer electrons  Chemical bonds – atoms interacting + staying close together 

 Weak chemical bonds are also important o Help reinforce shapes of large molecules + help molecules adhere to each other  Hydrogen bond – forms when hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom  In living cells, electronegative partners are usually O2 + N  Van der Waals interactions o When electrons are distributed asymmetrically in molecules or atoms, can result in ‘hot spots’ of positive or negative charge o Van der Waals interactions are attractions between molecules that are close together as a result of these charges  Ex. Geckos ‘sticking’ to walls Molecular Shape + Function  Shape determined by positions of atom’s valence orbitals  Biological molecules recognize + interact w/ each other w/ a specificity based on molecular shape o Molecules w/ similar shapes can have similar biological effects Chemical Reactions Make + Break Chemical Bonds  Chemical reactions – making + breaking of chemical bonds  Reactants + products  Chemical equilibrium is reached when forward + reverse reaction rates are equal