Transcript
BROOKLYN COLLEGE
Of The City University of New York
Spring 2011
Bio 1002 – General Biology 2 – Mon/Wed 3:40-4:55 pm, Room 113 NE
Sections: MW3A, MW3B, MW3AF, MW3C, MW3BF
Lecturer: Prof. Dan Eshel
Email: deshel@brooklyn.cuny.edu, Telephone: 718-951-5000, ext. 2015
Office Hours: Wednesday: 2-3 pm, Room 300 NE or by appointment.
Blackboard
This syllabus, all announcements, PowerPoint presentations and exam grades will be posted on the course page on CUNY’s Blackboard.
Course Requirements and Policies
Textbook: Biology by Campbell and Reece. Seventh Edition or newer.
Laboratory: All information regarding the laboratory part of this course will be given by your lab instructor.
Grading: Lecture and lab are 50% each of your final grade. Point distribution for lecture is as follows:
3 midterm exams, 12.5% each
Final exam (not cumulative) 12.5%
Lecture Exam Dates
Feb 23
Mar 23
Apr 27
Final: May 25
Lecture evaluation
Three midterm exams and a final exam will be given on the dates listed above. The exams will assess your ability to retain and recall the material covered in lecture as well as your ability to integrate and extrapolate the material covered by solving problems. All exams will consist of multiple choice questions.
There are no make-up exams. If you miss one exam it will be entered as a 0. Failure to take 2 exams constitutes an F for the course.
Attendance and Policies
-It is expected that students will attend every lecture.
-Tardiness is not a socially acceptable practice. You should be in your seat and set up before the instructor begins.
- If you miss a lecture you are responsible for the material covered.
-You are responsible for all announcements made in lecture. If you miss a class or come late, be sure you obtain missed information from a classmate.
-All initial inquiries regarding your grade for the course should be directed to the laboratory instructor.
-You are expected to turn off your cell phone before class starts.
PLEASE NOTE:
There are no negotiations for grades. Your grade is the sum of the components listed above. There will be no curving or scaling of grades. There are no extra credit, make-up or “pity” points. It is expected that you give 100% effort in all your endeavors including this course. Therefore there are no extra points for “working hard”.
How to succeed in Biology:
-Attend all lectures and labs.
-Read the text BEFORE class.
-Review your class notes as soon as possible after lecture and immediately before lecture.
-Know the vocabulary! The study of biology is like learning a new language. You need to know the vocabulary in order to understand the concepts.
Chapter 2
The Chemical Context of Life
Biology is a multidisciplinary science
Living organisms are subject to basic laws of physics and chemistry
Matter consists of chemical elements in pure form and in combinations called compounds
Organisms are composed of matter
Matter is anything that takes up space and has mass
Elements and Compounds
Matter is made up of elements
An element is a substance that cannot be broken down to other substances by chemical reactions
A compound is a substance consisting of two or more elements in a fixed ratio
A compound has characteristics different from those of its elements
Fig. 2-3
Sodium
Chlorine
Sodium
chloride
Essential Elements of Life
About 25 of the 92 elements are essential to life
Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter
Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur
Trace elements are those required by an organism in minute quantities
Table 2-1
Fig. 2-4a
(a) Nitrogen deficiency
Fig. 2-4b
(b) Iodine deficiency
Goiter
(thyroid enlargement)
An element’s properties depend on the structure of its atoms
Each element consists of unique atoms
An atom is the smallest unit of matter that still retains the properties of an element
Subatomic Particles
Atoms are composed of subatomic particles
Relevant subatomic particles include:
Neutrons (no electrical charge)
Protons (positive charge)
Electrons (negative charge)
Neutrons and protons form the atomic nucleus
Electrons form a cloud around the nucleus
Neutron mass and proton mass are almost identical and are measured in daltons
Cloud of negative
charge (2 electrons)
Fig. 2-5
Nucleus
Electrons
(b)
(a)
Atomic Number and Atomic Mass
Atoms of the various elements differ in number of subatomic particles
An element’s atomic number is the number of protons in its nucleus
An element’s mass number is the sum of protons plus neutrons in the nucleus
Atomic mass, the atom’s total mass, can be approximated by the mass number
Fig. 2-9
Hydrogen
1H
Lithium
3Li
Beryllium
4Be
Boron
5B
Carbon
6C
Nitrogen
7N
Oxygen
8O
Fluorine
9F
Neon
10Ne
Helium
2He
Atomic number
Element symbol
Electron-
distribution
diagram
Atomic mass
2
He
4.00
First
shell
Second
shell
Third
shell
Sodium
11Na
Magnesium
12Mg
Aluminum
13Al
Silicon
14Si
Phosphorus
15P
Sulfur
16S
Chlorine
17Cl
Argon
18Ar
Isotopes
All atoms of an element have the same number of protons but may differ in number of neutrons
Isotopes are two atoms of an element that differ in number of neutrons (same atomic number but different atomic mass)
Radioactive isotopes decay spontaneously, giving off particles and energy
Electron Distribution and Chemical Properties
The chemical behavior of an atom is determined by the distribution of electrons in electron shells
Atoms are electrically neutral: The number of protons equal the number of electrons
The periodic table of the elements shows the electron distribution for each element
Fig. 2-9
Hydrogen
1H
Lithium
3Li
Beryllium
4Be
Boron
5B
Carbon
6C
Nitrogen
7N
Oxygen
8O
Fluorine
9F
Neon
10Ne
Helium
2He
Atomic number
Element symbol
Electron-
distribution
diagram
Atomic mass
2
He
4.00
First
shell
Second
shell
Third
shell
Sodium
11Na
Magnesium
12Mg
Aluminum
13Al
Silicon
14Si
Phosphorus
15P
Sulfur
16S
Chlorine
17Cl
Argon
18Ar
Valence electrons are those in the outermost shell, or valence shell
The chemical behavior of an atom is mostly determined by the valence electrons
Elements with a full valence shell are chemically inert
The formation and function of molecules depend on chemical bonding between atoms
Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms
These interactions usually result in atoms staying close together, held by attractions called chemical bonds
Covalent Bonds
A covalent bond is the sharing of a pair of valence electrons by two atoms
In a covalent bond, the shared electrons count as part of each atom’s valence shell
Fig. 2-11
Hydrogen
atoms (2 H)
Hydrogen
molecule (H2)
A molecule consists of two or more atoms held together by covalent bonds
A single covalent bond, or single bond, is the sharing of one pair of valence electrons
A double covalent bond, or double bond, is the sharing of two pairs of valence electrons
The notation used to represent atoms and bonding is called a structural formula
For example, H–H
This can be abbreviated further with a molecular formula
For example, H2
Fig. 2-12a
(a) Hydrogen (H2)
Name and
Molecular
Formula
Electron-
distribution
Diagram
Lewis Dot
Structure and
Structural
Formula
Space-
filling
Model
Fig. 2-12b
(b) Oxygen (O2)
Name and
Molecular
Formula
Electron-
distribution
Diagram
Lewis Dot
Structure and
Structural
Formula
Space-
filling
Model
Fig. 2-12c
(c) Water (H2O)
Name and
Molecular
Formula
Electron-
distribution
Diagram
Lewis Dot
Structure and
Structural
Formula
Space-
filling
Model
Fig. 2-12d
(d) Methane (CH4)
Name and
Molecular
Formula
Electron-
distribution
Diagram
Lewis Dot
Structure and
Structural
Formula
Space-
filling
Model
Covalent bonds can form between atoms of the same element or atoms of different elements
A compound is a combination of two or more different elements
Bonding capacity is called the atom’s valence
Electronegativity is an atom’s attraction for the electrons in a covalent bond
The more electronegative an atom, the more strongly it pulls shared electrons toward itself
In a nonpolar covalent bond, the atoms share the electron equally
In a polar covalent bond, one atom is more electronegative, and the atoms do not share the electron equally
Unequal sharing of electrons causes a partial positive or negative charge for each atom or molecule
Fig. 2-13
? –
?+
?+
H
H
O
H2O
Ionic Bonds
Atoms sometimes strip electrons from their bonding partners
An example is the transfer of an electron from sodium to chlorine
After the transfer of an electron, both atoms have charges
A charged atom (or molecule) is called an ion
Fig. 2-14-1
Na
Cl
Na
Sodium atom
Chlorine atom
Cl
Fig. 2-14-2
Na
Cl
Na
Cl
Na
Sodium atom
Chlorine atom
Cl
Na+
Sodium ion
(a cation)
Cl–
Chloride ion
(an anion)
Sodium chloride (NaCl)
A cation is a positively charged ion
An anion is a negatively charged ion
An ionic bond is an attraction between an anion and a cation
Compounds formed by ionic bonds are called ionic compounds, or salts
Salts, such as sodium chloride (table salt), are often found in nature as crystals
Fig. 2-15
Na+
Cl–
Weak Chemical Bonds
Most of the strongest bonds in organisms are covalent bonds that form a cell’s molecules
Weak chemical bonds, such as ionic bonds and hydrogen bonds, are also important
Weak chemical bonds reinforce shapes of large molecules and help molecules adhere to each other
Hydrogen Bonds
A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom
In living cells, the electronegative partners are usually oxygen or nitrogen atoms
Fig. 2-16
? ?
?+
?+
? ?
?+
?+
?+
Water (H2O)
Ammonia (NH3)
Hydrogen bond
Van der Waals Interactions
If electrons are distributed asymmetrically in molecules or atoms, they can result in “hot spots” of positive or negative charge
Van der Waals interactions are attractions between molecules that are close together as a result of these charges
Molecular Shape and Function
A molecule’s shape is usually very important to its function
Biological molecules recognize and interact with each other with a specificity based on molecular shape
Molecules with similar shapes can have similar biological effects
Fig. 2-18a
Natural endorphin
Morphine (opiate)
Key
Carbon
Hydrogen
Nitrogen
Sulfur
Oxygen
Structures of endorphin and morphine
(a)
Fig. 2-18b
Natural
endorphin
Endorphin
receptors
Brain cell
Binding to endorphin receptors
Morphine
(b)
Chemical reactions make and break chemical bonds
Chemical reactions are the making and breaking of chemical bonds
The starting molecules of a chemical reaction are called reactants
The final molecules of a chemical reaction are called products
Fig. 2-UN2
Reactants
Reaction
Products
2 H2
O2
2 H2O
Some chemical reactions go to completion: all reactants are converted to products
All chemical reactions are reversible: products of the forward reaction become reactants for the reverse reaction
Chemical equilibrium is reached when the forward and reverse reaction rates are equal