1. Cool “Fires” Attract Mates and Meals
Fireflies use light, instead of chemical signals, to send signals to potential mates
Females can also use light flashes to attract males of other firefly species — as meals, not mates

2. The light comes from a set of chemical reactions, the luciferin-luciferase system
Fireflies make light energy from chemical energy
Life is dependent on energy conversions

3. Fireflies

4. Characteristics of organisms (light, pigment, sound, smell) are end products of chemical reactions
Chemical reactions are for the purpose of energy transformations. All reactions equal some form of transformation.

5. Energy

6. ENERGY AND THE CELL
Living cells are compartmentalized by membranes
Membranes are sites where chemical reactions can occur in an orderly manner
Living cells process energy by means of enzyme-controlled chemical reactions

7. 5.1 Energy is the capacity to perform work
Energy is defined as the capacity to do work
All organisms require energy to stay alive
Energy makes change possible

8. Kinetic energy is energy that is actually doing work
Heat = randomly moving molecules
Light, i.e. photosynthesis
Figure 5.1A
Potential energy is stored energy
Chemical energy = energy stored in the arrangement of atoms in molecules
Figure 5.1B

9. Laws of Thermodynamics

10. 5.2 How is chemical energy “tapped” by organisms?
Rearrangment of sugar molecules, releasing stored energy for cellular work
What makes a living organism an open system (?
Exchange of matter and energy with surrounds

11. 5.2 Two laws govern energy conversion
First law of thermodynamics (energy of conservation)
Energy can be changed from one form to another
However, energy cannot be created or destroyed, it is constant
Gasoline to the right get ignited, where does chemical energy end up?
Unspent chemical energy in unused gas
KE of spinning engine
Heat
Figure 5.2A

12. Second law of thermodynamics (entropy increases)
Energy changes are not 100% efficient
Energy conversions increase disorder, or entropy
Some energy is always lost as heat. See below: When gas is ignited PE is released causing flash of light and burst of heat, which heats up surrounding environment
Figure 5.2B

13. 5.2
Almost reactions produce heat, which is added to surroundings
All energy transfers follow 2nd law -> production of heat.

14. 5.3 Chemical reactions either store or release energy
Cells carry out thousands of chemical reactions
The sum of these endergonic and exergonic reactions constitutes cellular metabolism

16. Potential energy of molecules
There are two types of chemical reactions:
Endergonic reactions absorb energy and yield products rich in potential energy. Energy stored in covalent bonds of products.
i.e. photosynthesis, energy of sunlight to form organic compounds.
Products
Amount of energy INPUT
Potential energy of molecules
Reactants
Figure 5.3A

17. Amount of energy OUTPUT Potential energy of molecules
Exergonic reactions release energy and yield products that contain less potential energy than their reactants
Burning and cellular respiration, chemical energy of reactants released to form energy-poor products (heat and light)
Reactants
Amount of energy OUTPUT
Potential energy of molecules
Products
Figure 5.3B

18. Difference between Burning and Cell Respiration?
Burning = energy released all at once
Cell Resp. = Multiple steps of energy release

19. 5.4 ATP shuttles chemical energy within the cell
Most endergonic cellular reactions require small amounts of energy, rather than large amounts food in food storage molecules.
Food is like a $100 bill but you need $1’s.
In cellular respiration, some energy is stored in ATP molecules = small change. Transfer amounts of energy from exergonic , food energy-releasing reactions to endergonic.
ATP powers nearly all forms of cellular work
ATP molecules are the key to energy coupling

20. Adenosine triphosphate Adenosine diphosphate (ADP)
When the bond joining a phosphate group to the rest of an ATP molecule is broken by hydrolysis, the reaction supplies energy for cellular work (exergonic reaction)
Adenine
Phosphate groups
Hydrolysis
Energy
Ribose
Adenosine triphosphate
Adenosine diphosphate (ADP)
Figure 5.4A

22. Potential energy of molecules
How ATP powers cellular work
Phosphate group from ATP is one of the reactants and the energy source for endergonic reaction
Reactants
Products
Potential energy of molecules
Protein
Work
This energizing process is phosphorylation. ATP regeneration is the reverse process where ADP becomes ATP thru dehydration synthesis.

23. Dehydration synthesis
The ATP cycle – note the order of the cycle, exergonic into endergonic
Hydrolysis
Dehydration synthesis
Energy from exergonic reactions
Energy for endergonic reactions
Figure 5.4C

24. Energy conversations: Y or N
PE -> KE
Gas chem. E -> KE
Photosynthesis = KE -> chem. E.
Energy transformations = release heat E.
YES
Yes

25. HOW ENZYMES WORK
5.5 Enzymes speed up the cell’s chemical reactions by lowering energy barriers
Enzymes are large protein molecules that functional as biological catalysts, which speeds up reactions without being consumed.
For a chemical reaction to begin, reactants must absorb some energy
This energy is called the energy of activation (EA)
This represents the energy barrier that prevents molecules from breaking down spontaneously
Without this barrier, all ATP in your body could spontaneously combust.

26. A protein catalyst called an enzyme can decrease the energy barrier
EA barrier
Enzyme
Reactants 1
Products 2
Figure 5.5A

27. EA without enzyme EA with enzyme Reactants Net change in energy
Products
Figure 5.5B

28. 6 facts about enzymes
Protein molecule
Biological catalyst
Increases reaction rate
Not being used up
Does not add energy – lowers energy barrier
Speeds up metabolism for life processes

29. 5.6 A specific enzyme catalyzes each cellular reaction
Enzymes are selective
This selectivity determines which chemical reactions occur in a cell
Enzymes are specific and catalyze specific cellular reactions.

30. Reactant = the substrate
How an enzyme works
Reactant = the substrate
Active site = part of the enzyme that binds to substrate and facilitates reaction.
Substrate turns to product
Active site
Enzyme (sucrase)
Substrate (sucrose)
Glucose
Fructose 1 4
Enzyme available with empty active site
Products are released 3 2
Substrate is converted to products
Substrate binds to enzyme with induced fit
Figure 5.6
The enzyme is unchanged and can repeat the process

31. 5.7 The cellular environment affects enzyme activity
Enzyme activity is influenced by
temperature – some temp. speeds up reaction, but too much = denatures -> changes shape, and structure related to function
salt concentration – salt ions interfere with bonds
pH – extra H+’s interfere
Some enzymes require nonprotein cofactors
inorganic like metals, i.e. Magnesium for chlorophyll)
Some cofactors are organic molecules called coenzymes (vitamins)

32. 5.8 Enzyme inhibitors block enzyme action
Inhibitors interfere with enzymes
A competitive inhibitor takes the place of a substrate in the active site
A noncompetitive inhibitor alters an enzyme’s function by changing its shape
Substrate
Active site
Enzyme
NORMAL BINDING OF SUBSTRATE
Competitive inhibitor
Noncompetitive inhibitor
ENZYME INHIBITION
Figure 5.8

33. Irreversible inhibition/Negative Feedback
Inhibition is irreversible when there are covalent bonds but are reversible when there are Hydrogen bonds. Think of bond strength
Type of inhibition whereby enzyme activity is blocked by one of the products of the reaction it catalyzes
Too much of something, machine turns off, but once depleted, machine turns back on

34. 5.9 Connection: Some pesticides and antibiotics inhibit enzymes
Certain pesticides are toxic to insects because they inhibit key enzymes in the nervous system
Pesticide Malathion inhibits the enzyme acetylcholinesterase, involved in nerve transmission.
Many antibiotics inhibit enzymes that are essential to the survival of disease-causing bacteria
Penicillin inhibits an enzyme that bacteria use in making cell walls

36. 5.10 Membranes organize the chemical activities of cells
MEMBRANE STRUCTURE AND FUNCTION
5.10 Membranes organize the chemical activities of cells
Membranes organize the chemical reactions making up metabolism  
Cytoplasm
Figure 5.10

37. Membranes are selectively permeable
Membranes separate cells from outside environment, including the environment of other cells that perform different functions.
Membranes are selectively permeable
They control the flow of substances into and out of a cell
In eukaryotes partition function into organelles
Membranes can hold teams of enzymes that function in metabolism

38. 5.11 Membrane phospholipids form a bilayer
Phospholipids (are like fats) are the main structural components of membranes
They each have a hydrophilic (polar) head and two hydrophobic (nonpolar) tails
Head
Symbol
Tails
Figure 5.11A

39. B. Structure (Fluid mosaic model) (10nm.)
A. Functions
1. Regulates the movement of molecules into and out of the cell
2. Site of cell recognition and communication
B. Structure (Fluid mosaic model) (10nm.)
1. Phospholipids
a different types
b. Most common = phosphotidylcholine
c. Membrane fusion easily accomplished
d. Movement - 2 mm./sec.
2. Cholesterol - decreases fluidity of membrane

40. In water, phospholipids form a stable bilayer
The heads face outward and the tails face inward
Water
Hydrophilic heads
Hydrophobic tails
Water
Figure 5.11B

41. Plasma Membrane - all cells have them
- complex, dynamic structures, not passive
- differentially permeable

42. Going thru the membrane
If soluble in lipids, can pass = non-polar
If unsoluble in lipids, can’t pass without protein molecule help, = polar

44. 5.12 The membrane is a fluid mosaic of phospholipids and proteins
Phospholipid molecules form a flexible bilayer
Cholesterol and protein molecules are embedded in it
Carbohydrates act as cell identification tags
Mosaic = proteins
Fluid = individual molecules can more or less move freely laterally
Two sides with different proteins: glycoproteins and glycolipids.
Some proteins extend thru membrane and bind to cytoskeleton or extracellular matrix

45. The plasma membrane of an animal cell
Glycoprotein
Carbohydrate (of glycoprotein)
Fibers of the extracellular matrix
Glycolipid
Phospholipid
Cholesterol
Microfilaments of the cytoskeleton
Proteins
CYTOPLASM
Figure 5.12

46. 5.13 Proteins make the membrane a mosaic of function
Some membrane proteins form 1) cell junctions, 2) either attachment to other cells or internal cytoskeleton
Others 3) transport substances across the membrane (hydrophilic molecules)
Figure 5.13
Transport

47. Many membrane proteins are4) enzymes, catalyzing reactions
Some proteins function as 5) receptors for chemical messages from other cells
The binding of a messenger to a receptor may trigger signal transduction
Messenger molecule
Receptor
Activated molecule
Figure 5.13
Enzyme activity
Signal transduction

48. 6) Identification tags: particularly glycoproteins

49. 5.14 Passive transport is diffusion across a membrane
In passive transport, substances diffuse through membranes without work by the cell
They spread from areas of high concentration to areas of lower concentration
At equilibrium, molecules diffuse back and forth, but no net change in concentration
PE = concentration gradient
KE = movement of molecules
Molecule of dye
Membrane
EQUILIBRIUM
EQUILIBRIUM
Figure 5.14A & B

51. Different molecules diffuse independently of each another
Passive transport is an extremely important way for small molecules to get into and out of cells. For example, O2 moves into red blood cells and CO2 moves out of these cells by this process in the lungs.

52. 5.15 Osmosis is the passive transport of water
Hypotonic solution
Hypertonic solution
In osmosis, water travels from an area of lower solute concentration to an area of higher solute concentration
Osmosis can cause a physical force to be applied to the hypertonic solution. Force raises level of solution against force of gravity until weight difference in levels equals the osmotic force
Selectively permeable membrane
Solute molecule
HYPOTONIC SOLUTION
HYPERTONIC SOLUTION
Water molecule
Selectively permeable membrane
Solute molecule with cluster of water molecules
NET FLOW OF WATER
Figure 5.15

53. The direction of osmosis is determined only by the difference in total solute concentrations
Two solutions equal solute concentrations are isotonic to each other; therefore osmosis does not occur.
However, even in isotonic solutions separated by selectively permeable membrane, water molecules are moving at equal rates in both directions.

54. 5.16 Water balance between cells and their surroundings is crucial to organisms
Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution
The control of water balance (osmoregulation) is essential for organisms
Know terminology for plant/animal cells
ISOTONIC SOLUTION
HYPOTONIC SOLUTION
HYPERTONIC SOLUTION
ANIMAL CELL
(1) Normal
(2) Lysing
(3) Shriveled
Plasma membrane
PLANT CELL
Figure 5.16
(4) Flaccid
(5) Turgid
(6) Shriveled

55. Real life water issues Drinking too much saltwater = ?
Drinking too much fresh water = ?
High concentration in solution, water leaves cells = dehydrated
Low concentration in solution, water rushes into cells = lyses

56. 5.17 Transport proteins facilitate diffusion across membranes
Small nonpolar molecules diffuse freely through the phospholipid bilayer
Many other kinds of molecules pass through selective protein pores by facilitated diffusion .
A pored protein, spanning the membrane bilayer, allows solute to go down concentration gradient.
Solute molecule
Transport protein
Figure 5.17

57. The cell does not expend energy
The rate of facilitate diffusion depends on the number of such transport proteins, in addition to the strength of the concentration gradient.
Water is a polar membrane and therefore needs the assistance of transport proteins when crossing membranes.

58. 5.18 Cells expend energy for active transport
Transport proteins can move solutes across a membrane against a concentration gradient
This is called active transport
Active transport requires ATP to help the protein change its structure and thus move the solute molecule.
Active transport molecules often couple the passage of two solutes in opposite directions across the membranes.

59. Active transport in two solutes across a membrane
FLUID OUTSIDE CELL
Phosphorylated transport protein
Active transport in two solutes across a membrane
Transport protein
First solute 1
First solute, inside cell, binds to protein 2
ATP transfers phosphate to protein 3
Protein releases solute outside cell
Second solute 4
Second solute binds to protein 5
Phosphate detaches from protein 6
Protein releases second solute into cell
Figure 5.18

60. 5.19 Exocytosis and endocytosis transport large molecules
To move large molecules or particles through a membrane
a vesicle may fuse with the membrane and expel its contents (exocytosis)
FLUID OUTSIDE CELL
CYTOPLASM
Figure 5.19A

61. or the membrane may fold inward, trapping material from the outside (endocytosis)
Figure 5.19B

62. Material bound to receptor proteins
Three kinds of endocytosis
Pseudopod of amoeba
Food being ingested
Plasma membrane
Material bound to receptor proteins
PIT
Cytoplasm
Figure 5.19C
Cell mediated – receptors sense molecule and pinch around it

63. Chloroplasts and Mitochondria
The two are linked
Solar energy is used to build energy-rich molecules in endergonic reactions in chloroplasts.
Energy-rich molecules release their energy to form aTP in mitochondria
Chemicals involved as the reactants in chloroplasts are the products in mitochondria and vice-versa.
Energy in the form of heat is lost to the environment thus a constant supply of energy must be supplied to all organisms.