METABOLISM

METABOLISM

What is metabolism?

Total of all chemical reactions occurring within the

body

Categories of metabolic reactions

Catabolic reactions

Degradation pathways

Anabolic reactions

Synthesis pathways

2

METABOLISM

3

ENERGY

What is energy?

No mass; does not take up space

Has the capacity to do work (potential energy) or to

put matter into motion (kinetic energy)

Can be converted into different forms but is not

created or destroyed

4

ENERGY

What types of energy are there?

Chemical

Energy stored in chemical bonds

Electrical

Involves movement of charged particles

Mechanical

Involves movement of matter

Electromagnetic (radiant)

Energy traveling in waves

5

Quick Quiz: Potential energy can be

“stored” in all of the following forms

except…

A) Electromagnetic energy

B) Electrical energy

C) Mechanical energy

D) Chemical energy

6

ENERGY

Where does our energy for metabolism come from?

Chemical energy

Nutrients (food)

Electromagnetic energy

Heat (thermal)

Sun or geothermal sources

Visible light

7

ENERGY

Energy for cellular metabolism must be “refined”, or converted to useful types of energy

Photosynthesis

Electromagnetic energy (sunlight) chemical energy

Aerobic respiration

Chemical energy (chemical bonds of certain molecules) chemical energy (more usable form for cells)

8

ATP (adenosine triphosphate)

9

10

Quick Quiz: ATP is an example of

which of the following energy forms?

A) Electromagnetic energy

B) Thermal energy

C) Mechanical energy

D) Chemical energy

11

Energy Flow & Nutrient Cycling

in Biological Systems

Energy

1-way flow

Ultimately lost as

heat

Nutrients

Cycled

12

Nutrients

What are nutrients?

Chemical substances needed for normal metabolism &

growth

O C H N

Ca P K S Na Cl Mg I Fe

Organic vs. inorganic nutrients

Macronutrients

Proteins

Carbohydrates

Lipids

Nucleic acids

13

Quick Quiz: Which of the following is

NOT recycled in an ecosystem?

A) Carbon

B) Electromagnetic energy

C) Water

D) Nitrogen

14

ENZYMES

Chemical reactions

Reactants are converted into products

Atoms become combined in new forms

O2 + 2 H2 2 H2O

15

ENZYMES

Reaction rates

Typically too slow to sustain life

Need help to speed up

Enzymes are biological catalysts

Catalysts speed up reactions

They do not make a reaction happen that wouldn’t

have happened otherwise

Enzymes are usually made out of protein

16

ENZYMES

Reaction rates

Typically too slow to sustain life

Need help to speed up

Enzymes are biological catalysts

Catalysts speed up reactions

They do not make a reaction happen that wouldn’t

have happened otherwise

Enzymes are usually made out of protein

17

ENZYMES

In order to react, molecules go through awkward

transitions

Unstable, high-energy states: Transition states

Enzymes help to speed up reactions by stabilizing

transition states

18

Reactants:

2H2 O2

Activation energy

Difference between free energy

of reactants and products

Products: 2H2O

Time

Fre

e e

nerg

y

ENZYMES

Quick Quiz: True or false: An enzyme

makes a reaction that wouldn’t have

happened

A) True

B) False

20

Quick Quiz: The difference between

the amount of energy in reactants and

the maximal amount of energy in the

transition state is called…

A) Activation energy

B) Free energy

C) Catalyst

D) Potential energy

21

Photosynthesis

22

C6H12O6

Photosynthesis

Occurs in chloroplasts

Outer membranes (2)

Thylakoid membrane system

Stroma

23

Photosynthesis

Two distinct events

Light-dependent reactions (light reactions)

Occurs in thylakoids of chloroplasts

Energy from sunlight used to generate ATP &

NADPH

Splits H2O, releasing O2 as a byproduct

Light-independent reactions (dark reactions)

Occurs in stroma of chloroplasts

Uses CO2, ATP &

NADPH to synthesize

glucose

24

Photosynthesis

Process summary

25

Photosynthesis

How is light energy actually captured and

converted into chemical energy?

Photopigments capture photons of light

Chlorophylls (a, b)

Accessory pigments (carotenoids, phycobilins)

Electron carriers transfer energy to form ATP &

NADPH

Calvin-Benson cycle uses the ATP & NADPH to “fix”

CO2 into sugars (glucose)

26

Quick Quiz: Which stage of

photosynthesis requires carbon

dioxide?

A) Light-dependent reactions

B) Light-independent reactions

27

Quick Quiz: True or false: the goal of

photosynthesis is to produce oxygen.

A) True

B) False

28

Light-Dependent Reactions

Photopigments & the Electromagnetic Spectrum

29

Photopigments & the Electromagnetic Spectrum

30

Englemann’s Experiment

31

Light Capture & Energy Transport

Two photosystems for capturing light energy

32

Quick Quiz: In a plant cell, which of the

following is NOT where you would find

chlorophyll?

A) Photosystem I

B) Photosystem II

C) ATP synthase

D) Thylakoid membrane

33

Quick Quiz: What is the final product

of the “light reactions”?

A) glucose

B) starch

C) ATP

D) NADPH

E) C and D only

F) All of the above

34

Light-Independent Reactions

Calvin-Benson cycle

Occurs in stroma of chloroplast

Use ATP & NADPH generated during light-dependent

reactions

Carbon fixation

6 CO2 + 6 RuBP 1 glucose

Rubisco (enzyme)

35

RuBP = ribulose bisphosphate

36

Photosynthesis

Process summary

ATP + NADPH

37

C6H12O6

Quick Quiz: How many carbon atoms

does RuBP have?

(Just press the number on your

keypad that corresponds with your

answer.)

38

Quick Quiz: Which of these is a

product of the Calvin-Benson cycle

(aka the “dark-reactions” or “light-

independent reactions”)

A) ATP

B) glucose

C) NADPH

D) CO2

39

Variations to Photosynthetic Systems in Plants

Differences in environments (light intensity,

temperature, rainfall, soil conditions, etc) can

affect how photosynthesis proceeds in plants

How to deal with hot, dry conditions

40

Stomata

Allow gas exchange through leaves (O2, CO2,

H2O)

Close in hot dry weather to prevent excess water loss

Causes increase in O2 levels; decrease in CO2 levels

Triggers photorespiration (bad news!)

41

C3 Plants

E.g., evergreen trees (temperate zones)

With stomata closed…

Rubisco fixes O2 when CO2 levels drop

Efficiency reduced

by 1/2

42

C4 Plants

E.g., grasses, corn, tropical plants

Two carbon fixation steps

Each fixed in different types of cells

Maintain higher internal

CO2 levels in the cells that

make sugar than C3’s

Lose less water, make more glucose than C3 plants during hot/dry conditions

43

CAM Plants

E.g., cactus, desert plants

Stomata close during the day and open at night

Carbon fixation occurs at night

Most efficient under

hot/dry conditions

44

Quick Quiz: Which of the following

plants uses a 4-carbon molecule in the

Calvin cycle?

A) Corn

B) Douglas fir

C) Saguaro cactus

D) A and B

E) A and C

45

“The Circle of Life”

46

“The Circle of Life”

36 ATP

47

Aerobic Respiration

C6H12O6 + 6 O2 6 CO2 + 6 H2O + 36 ATP

glucose oxygen carbon dioxide water

48

Aerobic Respiration

Involves 3 linked processes

Glycolysis

Citric acid cycle

TCA (tricarboxylic acid cycle) / Krebs cycle

Oxidative phosphorylation

Respiratory transport chain / electron transport

chain

ATP synthase

49

Aerobic Respiration

50

Glycolysis

“Sugar splitting”

Occurs in cytoplasm

Net reaction:

1 glucose 2 pyruvate + 2 ATP + 2 NADH

C6H12O6 C3H3O3

51

Glycolysis (part 1)

52

Glycolysis (part 2)

53

Glycolysis

Bottom line…

1 glucose 2 pyruvate + 2 ATP + 2 NADH

Glucose (6 C) split into 2 molecules of pyruvate (3C)

To TCA cycle

54

Glycolysis

Bottom line…

1 glucose 2 pyruvate + 2 ATP + 2 NADH

Glucose (6 C) split into 2 molecules of pyruvate (3C)

Uses 2 ATP, produces 4 ATP net yield of 2 ATP

Available for immediate energy needs

55

Glycolysis

Bottom line…

1 glucose 2 pyruvate + 2 ATP + 2 NADH

Glucose (6 C) split into 2 molecules of pyruvate (3C)

Uses 2 ATP, produces 4 ATP net 2 ATP

Produce reducing potential (NADH)

To electron transport (oxidative phosphorylation)

56

Quick Quiz: The end result of

glycolysis is 2 molecules of ________.

A) Carbon dioxide

B) Oxygen

C) Glucose

D) Pyruvate

57

Quick Quiz: True or false: Plant cells

have mitochondria.

A) True

B) False

58

TCA Cycle

Occurs in mitochondria

Matrix (inner compartment)

Net reaction:

2 pyruvate 6 CO2 + 2 “ATP” + 8 NADH + 2 FADH2

59

TCA Cycle

60

TCA Cycle

Bottom line…

2 pyruvate 6 CO2 + 2 “ATP” + 8 NADH + 2 FADH2

Glucose now completely oxidized to CO2

Diffuses from cell

Generates lots of reducing potential (NADH, FADH2)

To electron transport chain (ETC)

61

Quick Quiz: Which of the following is

NOT a product (or byproduct) of the

TCA cycle?

A) NADH

B) FADH2

C) ATP

D) Pyruvate

E) CO2

62

Oxidative Phosphorylation

Occurs in mitochondria (inner membrane)

Most efficient system for ATP generation

Net reaction:

10 NADH + 2 FADH2 + 6 O2 32 ATP + 6 H2O

63

Oxidative Phosphorylation

64

ATP

ADP + Pi

INNER

COMPARTMENT

Oxidative Phosphorylation

65

Oxidative Phosphorylation

66

Oxidative Phosphorylation

Bottom line…

10 NADH & 2 FADH2 + 6 O2 32 ATP + 6 H2O

Use “energy carriers” (NADH, FADH2) from glycolysis and

TCA cycle to generate ATP

O2 is the terminal acceptor for the transferred electrons

Involves ATP synthase

Uses H+ concentration gradient

67

Aerobic Respiration

68

Quick Quiz: Where is the electron

transport chain located?

A) Cytoplasm

B) Mitochondrial matrix

C) Outer mitochondrial membrane

D) Inner mitochondrial membrane

E) Intermembrane space (outer compartment)

69

Quick Quiz: What would happen to

oxidative phosphorylation if oxygen

were not available?

A) Oxidative phosphorylation would cease

B) Oxidative phosphorylation would increase

C) Oxidative phosphorylation would occur at

the same rate

70

Anaerobic Respiration

ATP generation in the absence of O2

Involve terminal electron acceptors other than

oxygen

E.g., O-containing salts (nitrates, nitrites, sulfates,

sulfites)

Anaerobic bacteria

71

Anaerobic Respiration

ATP generation in the absence of O2

ATP produced through glycolysis with lactic acid

and/or ethanol and CO2 as end products

Fermentation

Lactic fermentation

Alcoholic fermentation

Decreased efficiency; have to deal with by-products

72

Lactic Fermentation

73

Alcoholic Fermentation

74

Alternate

Energy

Sources &

Biosynthesis

75

Quick Quiz: True or False – The TCA

cycle can only be used to oxidize

(process) pyruvate.

A) True

B) False

76