Photosynthesis

Photosynthesis

Process whereby green plants convert the radiant energy of light into chemical energy that is then stored in food molecules

light, carbon dioxide, and water

What do plants utilize to produce oxygen and carbohydrates?

Chloroplasts

Where does photosynthesis take place in?

Glucose

What is the main product of photosynthesis?

6 carbon dioxide, 12 water, and light energy

What are the reactants in the photosynthesis equation?

6 glucose, 6 oxygen, and 6 water

What are the products in the photosynthesis equation?

Chromatography; chromatogram

_______________ is a method of separating closely related compounds, as in the case of pigments, by allowing the mixture of substances to diffuse through an absorbent called _______________

Thylakoid membrane

Where does the light-dependent reaction happen?

Stroma

Where is the site of the Calvin cycle?

Light Dependent Reaction and Light Independent Reaction (Calvin Cycle)

What are the two stages of Photosynthesis

light and water

What is needed in the light-dependent reaction?

oxygen, atp, nadph

what are the outputs of the light-dependent reaction?

because it requires light to excite electrons

Why is it called a light-dependent reaction?

True

True or False

Photosystem II (PSII) occurs before Photosystem I (PSI), even if PSI was discovered first.

Photosystems

Composed of either integral or peripheral proteins embedded in the phospholipid bilayer.

Integral proteins

proteins that are embedded within the phospholipid bilayer of cell membranes; typically involved in transport and structural functions

Peripheral proteins

proteins found on the surface of the membrane; signaling and enzymatic activities.

Chlorophyll

absorbs light

PQ (Plastoquinone)

transfers electrons from PSII to Cytochrome complex.

Cytochrome complex

acts like a turbine, helps create a proton gradient

PC (Plastocyanin)

carries electrons to PSI

Ferredoxin (FD)

carries electrons to NADP+ reductase

NADP+ Reductase

enzyme that converts NADP+ to NADPH

Splitting of Water (Photolysis) Process

1. 2 electrons go to PSII.

2. 4 protons contribute to the gradient.

3. O₂ is released via stomata (must combine two ½ O₂).

4. O₂ diffuses out because it's a gas and can escape through the phospholipid bilayer.

Energy Transfer Process

1. Light excites electrons at PSII → PQ → Cytochrome → PC → PSI.

2. Electrons lose energy along the way and need re-excitation at PSI.

3. Energy from excited electrons drives protons (H⁺) into the lumen, creating a proton gradient.

4. ATP Synthase uses the proton gradient to convert ADP + Pi → ATP.

Chemiosmosis

Movement of H⁺ through ATP synthase to produce ATP.

Z-scheme

What is the flow of electrons from water → PSII → PSI → NADP+

atp, nadph, carbon dioxide

What is needed in the calvin cycle?

carbohydrates (glucose, starch)

What is the output of the calvin cycle

rubisco (RuBP)

What is the enzyme used during carbon fixation

Carbon Fixation Process

1. CO₂ attaches to RuBP (5-carbon compound) to form unstable 6-carbon.

2. Splits into two 3-carbon compounds (3-PGA).

1. Carbon Fixation

2. Reduction

3. Regeneration

What are the steps in Calvin Cycle?

Reduction Process

1. 3-PGA → G3P (Glyceraldehyde 3-phosphate).

2. Requires: ATP and NADPH.

3. From 3 CO₂ molecules → 6 G3P molecules.

   • 1 G3P is used to make glucose.

   • 5 G3P regenerate RuBP (cycle continues).

Regeneration Process

1. Uses ATP to convert G3P back to RuBP.

2. To make 1 glucose:

   • 6 CO₂, 18 ATP, 12 NADPH are needed.

False

True or False

Glucose can enter the mitochondria without being broken down to pyruvate

To remove chlorophyll pigments

Why do we soak the mayana leaves (Coleus sp.) in ethanol?

to soften the tissues and stops cellular activity or deactivate cellular processes

Why do we boil the mayana leaves (Coleus sp.) in water?

True

True or False

Iodine test detects starch, not glucose directly.

the more the intense the light, the higher the rate of photosynthesis and vice versa

What is the relationship between the intensity of light and photosynthesis?

the longer the wavelength, the less the energy and vice versa

What is the relationship between the wavelength of light and photosynthesis?

violet light

Which wavelength carries the most energy?

red light

Which wavelength carries the least energy?

thylakoid and intergranal lamella

Where is photosynthetic pigment found?

Photosynthetic Pigment

A coloured biological compound that is present in chloroplasts and photosynthetic bacteria, and which captures light energy for photosynthesis.

chlorophylls and carotenoids

What are the type of pigments present in chloroplasts?

Chlorophyll

pigment that gives plants their green colour by reflecting green light.

Carotenoids

pigment that gives plants their warm colour by reflecting red, orange, or yellow light.

to absorb visible light

What is the function of photosynthetic pigments?

380nm to 750nm

What is the range of the wavelength that photosynthetic pigments absorb light?

Phaeophytin

• A yellow-gray band color on the chromatogram

• It primarily functions as an electron acceptor, receiving electrons from the P680 phase after absorbing light.

Xanthophyll

• A yellow-brown band color on the chromatogram

• absorbs blue-violet light wavelengths and also transfers the energy to chlorophyll a

• it is also a pigment for light absorption.

Chlorophyll a

• A bright green/blue green band color on the chromatogram

• Used in the light phase of photosynthesis where it absorbs the photons and converts it to chemical energy.

• Absorbs blue and red light the most efficiently along with chlorophyll b.

Chlorophyll b

• A yellow green/olive green band color on the chromatogram

• accessory pigment used for absorbing light wavelengths that chlorophyll a has difficulty in absorbing

A. Carotene

B. Xanthophyll

C. Chlorophyll a

D. Chlorophyll b

Identify A, B, C, and D

By the distance they travel through the chromatogram (Rf)

Aside from band color, how else can pigments be identified?

Retention factor (Rf)

This value is the ratio that can be calculated and compared to identify unknown compounds

distance of pigment from origin / distance of solvent front from origin

How to compute for Rf

1. Carotene – 0.95

2. Phaeophytin – 0.83

3. Xanthophyll – 0.71

4. Chlorophyll a – 0.65

5. Chlorophyll b – 0.45

What are the known Rf values for each pigment?

A. Phaeophytin

B. Chlorophyll a

C. Chlorophyll b

Identify A. B, and C

Identifies the solubility of the pigment and the molecular weight

What does the distance travelled say about the pigment?

True

True or False

More soluble pigments and lighter molecular weighted pigments travel faster

Carotene

• yellow band color on the chromatogram

• used for photoprotection by reflecting excessive light towards the plant

False

True or False

ATP is produced during the Calvin cycle.

2 G3P molecules (carbohydrates or your glucose)

When carbon dioxide is fixed during the calvin cycle, what will be the product?

Iodine solution

What was the solution used to detect the presence of the product of Calvin cycle?

Carbonic Acid

What product was produced when you blew the straw in a phenol red solution?

False

True or False

In paper chromatography, Xanthophyl is the top/highest pigment observed.

True

True or False

Water > Ethanol > Iodine

False

True or False

The product of Calvin cycle is produced in the roots

NADP+

What is the final electron acceptor during photosynthesis?

Phenol Red

pH indicator that changes from yellow to red over pH below 6.8 (more acidic), and then turning a bright pink color above pH 8.2 (more basic)

the higher the distance, the lesser the intensity, the lower the photosynthetic rate

What is the relationship between the distance of light and photosynthesis?

It was reflected. Chlorophyll gives plants their green color because it does not absorb the green wavelengths of white light

Why was green color not absorbed by chlorophyll?