Energy and Life

1
Energy and Life

• Autotrophs
• Organisms that make their own food.
• Heterotrophs
• Organisms that can not make their own food, and
  obtain energy from the food that they eat.

2
ATP and ADP

• ATP
• Basic energy source.
• Energy is released then ATP looses a phosphate
  group.

3
ATP and ADP

• The third phosphate group is added and removed to
  store and release energy

4
Photosynthesis

• Do plants need light????
• Joseph Priestley and Jan Ingenhousz
• Based on their experiments, we know that plants
  need light to grow.

5
Photosynthesis

• The process of trapping light energy from the
  sun and converting it to chemical energy
  (Carbohydrates)

6
Photosynthesis -Light is the Key-

• Light from the Sun
• White (visible) light is
• a mixture of many
• colors (wavelengths)
• Visible light drives
• photosynthesis
• But are all colors
• (wavelengths) of light
• involved?

7
Photosynthesis -Colors of Light-

• Colors of Light
• We see objects as being certain colors because
  they reflect those colors
• What color are most plant leaves?
• So, what color do the leaves reflect?

8
Photosynthesis -Chlorophyll-

• Most leaves appear
• green because they
• have a pigment called
• chlorophyll that
• reflects green light
• This word comes from
• the Greek Chloros,which means yellowish green,
  and from -phyll for leaf

9
Photosynthesis Colors of Light Used

• Chlorophyll makes leaves appear green because
  it absorbs little green light
• (green is mostly reflected)
• As shown here,
• chlorophyll mostly
• absorbs red and blue light,
• the colors of light most
• effective for photosynthesis

10
Photosynthesis -How Chlorophyll Works-

• When chlorophyll absorbs light energy, an
  electron in chlorophyll is excited from a lower
  energy state to a
• higher energy state
• 
  This higher energy state is unstable and the
  electron cannot remain there for long

11
Photosynthesis -Electron Transfer-

• This excited electron is
• then transferred to another
• molecule and starts a chain
• of electron- transfer steps
• The process of light-
• harvesting occurs in an
• organization of pigments,
• proteins and other organic
• molecules called a
• photosystem

12
Photosynthesis -Photosystem Location-

• The chlorophyll and
• other molecules that
• make up a
• photosystem are
• located in cell
• organelles called
• chloroplasts

13
Photosynthesis

• Inside of the chloroplasts are stacks of
  membranes called thylakoids.
• This is where the actual conversion of light
  energy to chemical energy occurs.

14
Photosynthesis -Photosystems 1 and 2-

• The excited, high energy electron can be used by
  the cell to perform work.
• Essentially, solar power is used to generate ATP
  and NADPH, which provide chemical and reducing
  power, respectively, for sugar- making reactions.
• An incidental by- product of these reactions is
  oxygen.

15
Photosynthesis -The Calvin Cycle-

• Also know as
• Light-Independent reaction
• ATP and NADPH power the Calvin Cycle Carbon
  fixation occurs Molecules of inorganic
• CO 2 and H 2 0 are
• connected to produce
• Glucose (a high-energy sugar).

16
Photosynthesis -In summary-

• Photosynthesis
• The process of trapping light energy from the sun
  and converting it to chemical energy
  (Carbohydrates)
• TWO SEPARATE REACTIONS-
• LIGHT REACTION- USES CHLOROPHYLL
• CALVIN CYCLE- SUGARS ARE FORMED
• Overall Equation
• 6CO2 12H2O LIGHT ? C6H12O6 6O2 6H2O
• Carbon dioxide Water Glucose
  Oxygen Water
• The Sugars produced can then be used in
  respiration
• to provide.

17
Cellular Respiration

• THE PROCESS BY WHICH FOOD IS BROKEN DOWN TO
  RELEASE ENERGY.
• Glycolysis
• One molecule of glucose is broken in half
  producing two molecules of pyruvic acid
• Produces 2 molecules of ATP

18
Cellular Respiration

• In the absence of Oxygen
• Anaerobic Respiration
• Alcoholic Fermentation
• Used by yeast and a few other microorganisms
• End waste products Ethyl Alcohol and CO2
• Lactic Acid Fermentation
• End waste product Lactic Acid
• Exercise?
• Lactic Acid is produced by your muscles during
  rapid exercise when your body runs out of oxygen
  for your tissues.

19
Cellular Respiration

• In the presence of Oxygen
• Aerobic Respiration
• Requires oxygen to produce energy.
• Krebs Cycle (AKA Citric acid cycle)
• Pyruvic acid is broken down into carbon dioxide
  in a series of energy-extracting reactions.
• Electron Transport Chain
• Uses the high-energy electrons from the Krebs
  Cycle to convert ADP to ATP (Energy).

20
Cellular Respiration

• In summary
• Overall Equation
• 6O2 C6H12O6 ? 6CO2 6H2O Energy
• The products of photosynthesis are similar to the
  reactants of cellular respiration and the
  products of cellular respiration are the
  reactants of photosynthesis.
• Total number of ATP molecules formed during
  cellular respiration 36
• That is only 38 of the total energy in 1
  molecule of glucose.
• Where does the rest of it go?
• It is released as heat. Which is why your body
  feels warmer after vigorous exercise.

21
Enzymes

• Catalysts speed up a chemical reaction by
  lowering energy barriers
• Large proteins
• Names end in ase and are often named after their
  substrate

22
Enzyme-substrate complex

• An enzyme acts upon a specific compound called a
  substrate
• The enzyme will bind at an active site on the
  substrate just like a key in a lock
• The enzyme stays at the active site until the
  reaction reaches completion
• At the end the substrate changes into the product
  and the enzyme is released unchanged

23
Enzyme (hexokinase
Glucose
Substrates
ADP
Products
Glucose-6- phosphate
ATP
Products are released
Active site
Substrates bind to enzyme
Enzyme-substrate complex
Substrates are converted into products
24
Enzymes-special Proteins

• Enzymes are proteins that act as biological
  catalysts.    Enzymes speed up chemical reactions
  that take place in cells. Like other catalysts,
  enzymes act by lowering the activation energies,

Reaction pathway without enzyme
Reaction pathway with enzyme
25
Enzymes

• Substrate- site on an enzyme which binds to the
  enzyme.
• Active site is on the enzymes.
• Enzymes and substrates are like locks and keys.
  Each is specific.