BIO/PLS 210

Jan Smalle

jsmalle@uky.edu

Website: Smalle Lab(http://www.uky.edu/~jasmal3/)

Syllabus

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http://www.uky.edu/~jasmal3/

TEACHING

PLS 210 Resources

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Results of the quiz discussed at the beginning of the next lecture

PLS/BIO210 Grades distribution over the past 7 years:

A: 21% (16-28%)

B: 21%

C: 28%

D: 22%

E: 8% (0-13%)

The Chemistry of LifeChapter 2

David Latimer and his bottle garden

Photosynthesis and Respiration

Photosynthesis:

6CO2 + 6H2O + energy C6H12O6 + 6O2

Respiration:

C6H12O6 + 6O2 6CO2 + 6H2O + energy

Atomic Particles

Particle Charge Mass Units Location

Proton + 1 Nucleus

NeutronNo

electrical charge

1 Nucleus

Electron -Negligible(0.0005 units)

Orbitals around nucleus

Twelve Most Common Elements in Living Organisms

Element Symbol Number of Protons

Hydrogen H 1

Carbon C 6

Nitrogen N 7

Oxygen O 8

Sodium Na 11

Magnesium Mg 12

Phosphorus P 15

Sulfur S 16

Chlorine Cl 17

Potassium K 19

Calcium Ca 20

Iron Fe 26

hydrogen

carbon

• Hydrogen has one proton and one electron located in one orbital surrounding the nucleus.

• Carbon has six protons and (thus) six electrons. One electron pair is located in the inner orbital. The other four are distributed over four outer orbitals organized in a tetrahedron structure.

hydrogen

carbon

• Carbon has six protons and (thus) six electrons. One electron pair is located in the inner orbital. The other four are distributed over four outer orbitals organized in a tetrahedron structure.

• Electrons of the Carbon atom are distributed over two energetically different electron shells.

Covalent Bonds

• Single bond– Atoms share two electrons– Represented by single line (-) in

structural formula

H - C - H

H

H

Methane

Overall Photosynthesis Reaction

6CO2 + 6H2O + energy C6H12O6 + 6O2

Carbon dioxide Water Glucose Oxygen

Overall Photosynthesis Reaction

6CO2 + 6H2O + energy C6H12O6 + 6O2

24 C-O bonds+

12 H-O bonds

36 covalent bonds

7 C-O bonds+

5 C-C bonds+

7 C-H bonds+

5 H-O bonds+

12 O-O bonds

36 covalent bonds

Overall Respiration Reaction

C6H12O6 + 6O2 6CO2 + 6H2O + energy

24 C-O bonds+

12 H-O bonds

36 covalent bonds

7 C-O bonds+

5 C-C bonds+

7 C-H bonds+

5 H-O bonds+

12 O-O bonds

36 covalent bonds

hydrogen

carbon

• Carbon has six protons and (thus) six electrons. One electron pair is located in the inner orbital. The other four are distributed over four outer orbitals organized in a tetrahedron structure.

• Electrons of the Carbon atom are distributed over two energetically different electron shells.

Electron energy levels

Carbon (C) Oxygen (O) Inner shell

(Low potential energy)

Outer shell

(high potential energy)

Nitrogen(N)

NucleusElectron

Carbon: six protons and six electrons

Nitrogen: seven protons and seven electrons

Oxygen: eight protons and eight electrons

Carbon (C) Carbon (C)

Inner shell

(Low potential energy)

Outer shell

(high potential energy)

C-C bond

Carbon (C) Carbon (C)

C-C bond

Electron energy levels

Carbon (C) Oxygen (O)

Inner shell

(Low potential energy)

Outer shell

(high potential energy)

Oxygen has 8 protons in its nucleus. The result is a higher positive charge that exerts a stronger attraction force on the electrons of the outer shell. On average, these electrons will be located closer to the nucleus (compared to Carbon).

Carbon (C) Oxygen (O)

Inner shell

(Low potential energy)

Outer shell

(high potential energy)

C-O bond

Carbon (C) Oxygen (O)

C-O bond?

No !

Yes !

C-O bond?

No !

Yes !

C O

- Oxygen has a higher electronegativity than Carbon (Oxygen nucleus has 8 protons compared to 6 in the carbon nucleus. The higher proton number results in a higher positive charge).

- Electron pair is pulled towards the O nucleus

- Bonding electron pair contains a lower level of potential energy compared to when it is in the middle between nuclei (see waterfall analogy).

High potential energy

Earth center

Gravitational force

Low potential energy

Waterfall analogy

LAKE

RIVER

C

O

C

C

High potential energy

Low potential energy

Electrical force

Electrical force

C

O

C

C

Carbon-Carbon bonds contain useful energy

Bonding electron pair of C-C contains more energy than C-O pair

Hydrogen (H) Carbon (C)

Inner shell

(Low potential energy)

Outer shell

(high potential energy)

H-C bond

Hydrogen (H) Carbon (C)

Inner shell

(Low potential energy)

Outer shell

(high potential energy)

The potential energy of the bonding electron pair of a H-C bond is defined by the distance to the C nucleus. The distance to the H nucleus is in this case irrelevant since the single electron orbital of the H atom already defines the lowest possible energy state of an electron (or electron pair).

H-C bond

The potential energy of the bonding electron pair of a H-C or H-O bond is defined by the distance to the C or O nucleus. The distance to the H nucleus is in this case irrelevant since the single electron orbital of the H atom already defines the lowest possible energy state of an electron (or electron pair).

H-O bond

H

O

H

C

Carbon-hydrogen bonds contain useful energy

Bonding electron pair of C-H contains more energy than H-O pair

C

C

Basis of photosynthesis:Light energy is used to transform C-O and H-O bonds into C-C and H-C bonds + Energy

C

O

+ Energy

Basis of respiration:Energy is liberated by transforming C-C and C-H bonds into C-O and H-O bonds

+ +

C

C

+ +

Increased potential energy

Decreased potential energy

H

C

H

C

H

O

C

O

H

O

Photosynthesis and Respiration

Photosynthesis:

6CO2 + 6H2O + energy C6H12O6 + 6O2

Respiration:

C6H12O6 + 6O2 6CO2 + 6H2O + energy