Photosynthesis and Cellular Respiration

(Fall 2018)

Energy is the ability to do work.Without the ability to obtain & use

energy, life would NOT exist!One of the most important

compounds that cells use to store and release energy is adenosine

triphosphate (ATP).

ATP consists of:- Adenine (Nitrogen base)- Ribose (a 5-carbon sugar)- 3 Phosphate groups

ATP can easily release and store energy by breaking and reforming the bonds between its phosphate

groups.

Releasing EnergyCells release the energy stored in ATP by breaking the bonds between the 2nd and 3rd phosphate groups

Storing EnergyAdenosine diphosphate (ADP) has 2 phosphate groups instead of 3- Contains some energy (not as much as ATP)- When a cell has energy available, it stores small

amounts by adding a phosphate group to ADP, making ATP

- ADP is like a rechargeable battery!

Battery Metaphor- Turning ADP into ATP =

storing energy = fully charged battery

- Turning ATP into ADP = releasing energy = used battery

Hetero- vs. AutotrophsAutotrophs - make their own food from energy absorbed from the sunHeterotrophs - get their food from the food that they eat - cannot make their own food

PhotosynthesisPhoto - “light”Synthesis - “to make or create”

→ So, photosynthesis is the the process plants use to make their food (glucose) using energy from sunlight

Sunlight- Energy from the sun travels to Earth in the form

of light- Sunlight is a mixture of different wavelengths

and make up a color spectrum

Pigments- Plants gather the sun’s energy with

light-absorbing molecules - pigments- Plants’ main pigment is chlorophyll

- Two types:- Chlorophyll a- Chlorophyll b

Marker Chromatography

Lab

Plant Pigment Chromatography

Lab

Plants do NOT absorb in the green region.Leaves reflect green light, which is why

plants look green.

Photosynthesis6CO2 + 6H2O + energy → C6H12O6 + 6O2carbon dioxide / water / light → glucose / oxygen

Main Photosynthesis Factorscarbon dioxide / water / light → glucose / oxygen

Water- If plants lose

water… they can’t make food

- This is why plants have a waxy cuticle

Temperature- Process requires

enzymes which have an optimal temperature range of 0-35℃

Light Intensity- Increasing this

increases photosynthesis… until a max rate is reached

1.Light Dependent Reactions

In the chloroplasts’ thylakoids...

Chloroplasts◉ Chloroplasts are found mostly in special cells in the top half

of the leaf called the palisade cells. ◉ They are organelles that contain lots of little sacs called

thylakoids that are filled with a pigment called chlorophyll◉ Chlorophyll is responsible for absorbing the BLUE and

RED light responsible for photosynthesis. ◎ Because green is reflected, we see plants as green!

Light Dependent ReactionsIn the thylakoids:◉ Light energy is absorbed by the chlorophyll◉ Water enters to help with reaction◉ Energy is bound to special molecules called ATP

and NADPH◉ Oxygen is released.

2.Light Independent Reactions

In the chloroplasts’ stroma...

Light Independent Reactions[Also called the Calvin Cycle]In the stroma (fluid inside chloroplasts):◉ Energy from ATP and NADPH is used to convert

CO2 to glucose

ATP[Adenosine Triphosphate]There is a LOT of energy released when a phosphate group is removed, forming ADP + P

**You do not need toworry about NADPH!

Cellular Respiration

Cellular RespirationDefinition: The process by which energy is extracted from the food an organism eats (glucose)

HAPPENS IN ALL EUKARYOTIC CELLS plants AND animals!

Cellular RespirationC6H12O6 + 6O2 → 6CO2 + 6H2O + energy glucose / oxygen → carbon dioxide / water / energy

Look familiar??

Cellular RespirationThree Steps1. Glycolysis2. Citric Acid Cycle (or Krebs Cycle)3. Electron Transport Chain

1.Glycolysis

In the cytoplasm...

GlycolysisIn the cytoplasm [fluid inside cell, not in an organelle]:◉ One molecule of glucose (6 carbons) is split into

two pyruvate molecules (3 carbons each)◉ Energy released from splitting the glucose

molecule is bound into 2 ATP molecules

2.Citric Acid Cycle/Krebs Cycle

In the mitochondria...

Citric Acid/Krebs CycleInside the mitochondria:◉ One pyruvate molecule (3 carbons) enters◉ Splits into three CO2 molecules◉ 1 ATP is produced

SO... for every molecule of glucose (2 pyruvate molecules): 6 CO2 and 2 ATP produced

3.Electron Transport Chain

In the mitochondria...

Electron Transport ChainInside the mitochondria:

◉ Complex series of reactions… ◉ O2 (oxygen) enters◉ H2O (water) leaves◉ About 34 ATP molecules are produced per

glucose molecule

What about if there is no oxygen?

Anaerobic RespirationMaking energy from food when there is no oxygen!Some organisms make carbon dioxide and ethyl alcohol (like yeast)Other organisms (like us) make lactic acid… that’s why your muscles burn after a workout!

Anaerobic Respiration◉ occurs in the cytoplasm of cells.◉ 2 types of Fermentation exist:

○ -Alcoholic Fermentation○ -Lactic Acid Fermentation

◉ Under anaerobic conditions, fermentation follows glycolysis.

Respiration Pathways1. Glucose → pyruvic acid → CO2 + H2O + 36 ATP2. Glucose → pyruvic acid → CO2 + ethyl alcohol + 2 ATP3. Glucose → pyruvic acid → lactic acid + 2 ATP

Alcoholic Fermentation◉ Yeast & a few other microorganisms use alcoholic

fermentation to produce ethyl alcohol & carbon dioxide.

◉ Used to produce alcoholic beverages & causes bread dough to rise.

Chemical equation: Glucose→Pyruvic acid → Ethyl Alcohol + CO2 + 2ATP

Lactic Acid Fermentation◉ Most organisms carry out fermentation that converts

pyruvic acid to lactic acid.○ (including humans during exercise)

Chemical equation:Glucose →Pyruvic acid → Lactic acid + 2ATP