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BIS2A – W
Lecture 03
Bonds and Water
1 https://youtu.be/IsBZx0tv6dQ
1.1 Explain the nature of the different types of molecular bonds associated in biomolecules. 1.2 Define the “steady state” of a reaction and explain what happens when the “steady-state” is perturbed. 1.3 Explain the concept of equilibrium and what the equilibrium constant K represents. 1.4 Define pH, and understand the relationship between pH and water to predict the potential influence of changes of pH on biomolecules. Be able to use the 1.5 Define pKa and understand how pH can influence the protonation state of an acid or base. 1.6 Explain how water is used for condensation and hydrolytic reactions. 1.24 Define electronegativity and explain how this concept is used to predict bonding patterns and how two atoms interact. Learning Goals Lecture 03
Predominant atoms in biomolecules
98% of the mass of every living organism is made up of the following six elements:
- Carbon (C)
- Hydrogen (H)
- Nitrogen (N)
- Oxygen (O)
- Phosphorus (P)
- Sulfur (S) 3
How do atoms interact? How do molecules interact?
- (^) different icon^ differentrow
Sketch Pads Draw an ionic bond and covalent bond Show where the electrons are
6 Question: What is electronegativity? Can you rank the following atoms from least to most electronegative: C, H, N, O, P, S more pull less pull
Electrons are not always shared equally
7 more pull less pull
Consequences of electronegativity:
**1. Ionic bonds
- Polar covalent bonds VS non-polar covalent bonds
- Hydrogen-bonding**
te"pull"ofan^ atom to^ attractan electron 342156
lonic Bond^ Na-
covalentBond^02 A^ polar 1-> H^ nompolar
C-C H-O
Equal sharing of the electrons. Unequal sharing of the electrons. What do the d+ and d- represent? Polar covalent VS Nonpolar covalent
Polar covalent VS Nonpolar covalent
H-O
15
- What do the different letters represent?
- The lines between the letters represent bonds. What type of bond is represented by a solid line and what are its characteristics?
- What do the dots represent
- Where would we draw the dipoles on this compound?
Question 3.
Copy this in your sketch pad
Consequences of electronegativity:
**1. Ionic bonds
- Polar covalent bonds VS non-polar covalent bonds
- Hydrogen-bonding**
carboxylic 8 - - i I (^) ↑ ↑ (^) covalent bond are very ciscans
arere
pairs side group Strong love e molecule)
- What type of bond is represented by a dotted line and what are its characteristics?
- What types of compounds can dissolve in water? 17
Let’s look at a simple molecule, water.
Question 3.
18 From your pre-lecture assignment: why don’t nonpolar molecules interact with water? Question 3.
Hydrogen bonds are not limited to water
19
http://159.226.64.162/image/ be7c38ad6eed&groupId=30728&t=1383295384637image_gallery?uuid=998a9601- 1045 - 4276 - 87f2- Glycolytic bonds
- What type of Molecule is this?
- Below is a diagram of cellulose. What type of bonds are indicated by the red dotted lines?
- Are they intermolecular, intramolecular or both? 20
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by hydrogen^
bonds! hydrogen bonds Both carbohydrate G-2 is^ stronger^ than onlynas" A^ = (^) A-T, because here are^ a^ Bonds^ in^ a^ =c hydrogen bonds^ are transient->^ easily formed? easily bowen
Question: What does Steady-State mean? What is an equilibrium? How do we represent an equilibrium? A B Keq Keq=[B]/[A]
Recall…. 27 =
Brief review of pH from the reading assignment 28
For the sake of simplicity, we write 29 H 2 O <-----> H
and define pH = - log 10 [H
]
an equilibrium) interactions aredoneroute
no notchange in^ A^ or^ B.
University of California, Davis: Facciotti M.T. © Understand this concept! From the book. How much more or less is the proton concentration in a solution that has a pH = to one that has pH = 7? For instance: 30
