Cell Biology:
Cell Compounds and Biological Molecules
Lesson 2 – Acids, Bases, and Buffers (Inquiry into Life pg. 29-30)
Today’s Objectives

Describe the role of acids, bases, and buffers in biological
systems in the human body, including:


Differentiate among acids, bases, and buffers
Describe the importance of pH to biological systems in the
human body
Acids and Bases


When water ionizes, it releases an equal number of
hydrogen ions (H+) and hydroxide ions (OH-).
Ionization is the process of converting an atom or
molecule into an ion by adding or removing charged
particles such as electrons or ions
Acids and Bases

Acidic Solutions (High H+ Concentrations)

Acids are substances that dissociate in water, releasing
hydrogen ions (H+).

An example:
HCl
hydrochloric acid
H+ + Cl-
Acids and Bases

Basic Solutions (Low H+ Concentrations)

Bases are substances that dissociate in water, releasing
hydroxide ions (OH-) or take up hydrogen ions (H+).

An example:
NaOH
sodium hydroxide
Na+ + OH-
Acids and Bases

The pH Scale

Ranges from 0 - 14

A pH below 7 is acidic [H+] > [OH-]

A pH above 7 is alkaline

A pH of 7 is neutral
[OH-] > [H+]
[H+] = [OH-]
The pH Scale
Acids and Bases

The pH Scale

Each unit change in pH represents a change of 10X
Buffers and pH


A buffer is a chemical(s) that keep pH within normal
limits.
Bicarbonate ions (HCO3-) and carbonic acid (H2CO3)
found in human blood buffers the pH to 7.4




If bloods pH drops to 7, acidosis results
If blood pH rises to about 7.8, alkalosis results
Both conditions can be life threatening
Our bodies produce natural buffers that help keep our
blood at a healthy pH
Buffers and pH
If hydrogen ions (H+) are added to the blood,
this reaction occurs:
H+
+ HCO3bicarbonate ion
H2CO3
H+ ions removed from
blood, raises pH
If hydroxide ions (OH-) are added to the
blood, this reaction occurs:
OH- + H2CO3
carbonic acid
HCO3- + H2O
OH- ions removed
from blood, lowers
pH
Homework




Read pg. 31-40 – Carbohydrates, Lipids, Proteins, Nucleic
Acids
Create Flashcards for all bold terms found in these
pages
Each flash card should have the word on the front side
The back side should have:




Picture/diagram
Function
Composition
Location