Photosynthesis Biology

WE Want to Be able to 1) Describe structures and substates required for photosynthesis, 2) Understand the nature of light and how it is absorbed, 3) Understand how light energy is converted to chemical energy, 4) Describe the Calvin Cycle and Carbon Fixation. Textbook Connections: Chapter 8 Photosynthesis

Heterotrophs examples and function

Obtain energy from the organic molecules they eat (Ie animals, fungi, and most bacteria) They could do then do cellular respiration to create ATP

QUIZ: Heterotrophs use organic molecules produced by other organisms (T/F)

True

If it takes energy to create sugars, where to heterotrophs get these sugars from?

Autotrophs (Primary producers). Make organic -C, do photosynthesis and respiration

Photoautotrophs use what to make food

Use sunlight to make food (EX. plants, algae, cyanobacteria)

Photosynthesis equation

6Co2 + 6H2o ——> C6H12O6 + 6O2

Photosynthesis uses ______ ______ to produce sugar from carbon dioxide and water. O2 is a waste product

Solar Energy

Plants: Photosynthetic Reactions

How do plants source the reactants needed

1) ___ is absorbed by the roots from the soil

2) ___ is aquired from the air as a result of gas exchange through the stomata(small pores on the leaf underside)

3) Likewise, the ___ waste products exits through the stomata

4) _____

H2o, Co2, O2, Sunlight

Light Energy

Electromagnetic energy, composed of photon particles that travel as waves

Longer wavelengths (crests farther apart) carry ____ energy,

Shorter wavelengths carry _____ energy

less, more

What is light energy measured in and how is the color spectrum described interns of wavelengths and energy

Wavelength measured in nm (nanometer; 10^9 m; 1 billionth)

In the visible range (700-400nm), the violets have the shortest wavelengths (and most energy) and the reds have the longest

Solar light spectrum from the sun

Most intense wavelengths from the sun are visible, also the range photosynthesis takes advantage of

Absorption of Light

When a substance takes in light energy, usually causing its electrons to gain energy. Objects appear the color of what is NOT absorbed (reflected)

Photosynthetic pigments each absorb (gain energy) specific wavelengths of light; observed by its _____

absorbance spectrum

The main pigments of thylakoid membranes are:

chlorophyll a, chlorophyll b, B-carotene

Chlorpphyll

Chlorophyll a and b capture light for photosynthesis, the reason leaves are green (green wavelengths are reflected)

Caretenoids

B-carotene helps to protect photosystems by dissipating excess energy, also found in cells of carrots and oranges

QUIZ: Which colors of visible light can plants utilize

White

Red

Blue

Green

White, red, blue

Photosynthesis equation

Carbon Dioxide + Water —→ Sugar + oxygen

Just like cellular respiration, photosynthesis invovles complex metabolic pathways with _________

e- transfer steps

The two metabolic pathways of photosynthesis are

The light reactions, The Calvin cycle

The light Reactions

Convert light energy to chemical energy, energy capture/gain by the cell, high energy ATP and NADPH (e- carrier) formed, occurs in the thylakoid membranes of cholorplasts

What do light reactions do in general

cover light energy to chemical energy

Where do light reactions occur

thylakoid membranes of chloroplasts

The Calvin Cycle

Uses ATP and NADPH to make sugar, light-independent, energy required (from light), sugars created, occurs in the stroma of chloroplasts

What does the Calvin Cycle do in general

uses ATP and NADPH to make sugar

Calvin Cycle characteristics

light-independent, energy required (from light), sugars created, occurs in the stroma of chloroplasts

Where does the Calvin Cycle Occur

Stroma of chloroplasts

Chloroplasts structure

Double membrane (outer and inner)

Stroma - Inner fluid space

Grana - Stacks of thylakoids

Thylakoids - membrane bound structures with pigments where light reactions occur

Photosynthesis Part 1 - Light Reactions

Chorlophylls absorb light energy, turn light into chemical energy as ATP and NADH (will support sugar formation later), Occurring in thylakoid membrane in chloroplasts

The light reactions consist of Photosystem II and I (occur as II then I)

Light energy in needed for PS Ii and PS I

PS II

Photon absorbed by chlorophyll, splits water into waster O2, PSII releases e- to ETC

H+ is pumped into thylakoid space via ETC (PS II)

Proton gradient Established

PS I

E- finally transferred to NADP+ to create NADPH

— Highly reduced NADPH Formed

PS II

Photon absorbed by chlorophyll, splits water into waster O2, PSII releases e- to ETC

H+ is pumped into thylakoid space via ETC (PS II)

Proton gradient Established

PS I

E- finally transferred to NADP+ to create NADPH

— Highly reduced NADPH Formed

Photosynthesis Part 1 - Light reactions

Just like the ETC of Cellular respiration,

__ gradient is created as e- fall down the chain

Building PE

ATP synthase uses to gradient to generate ATP (chemioosmosis)

H+

Photosynthesis part 2 — Calvin Cyle

The ATP and NADPH from the light dependent reactions are made in the stroma for use in the Calvin cycle (sugar formation)

QUIZ:

Choose the correct order that the complexes would be used during the light reactions of photosynthesis.

(PS = photosystem)

PSII, ETC, PSI, ATP synthase 

ETC, PSII, PSI, ATP synthase

PSI, ETC, PSII, ATP synthase

PSI, PSII, ETC, ATP synthase

PSII, ETC, PSI, ATP synthase 

QUIZ: PSI (photosystem 1) can do all of the following EXCEPT

split water to generate an e- to ETC 

transfer electron to NADP+ to create NADPH

capture light energy to excite a central electron

receive electrons from the ETC

split water to generate an e- to ETC 

QUIZ: Photisystems (select ALL that apply)

Concentrate light energy into a single excited electron

Are large complexes of pigments

Can absorb energy from photons

Are food in the stroma of the chloroplast

Concentrate light energy into a single excited electron

Are large complexes of pigments

Can absorb energy from photons

QUIZ: Which of the following is the main output of the Calvin cycle:

Oxygen

g3P (glycerahyde 3 phosphate)

RuBP

Glucose

g3P (glycerahyde 3 phosphate)

QUIZ: Match the following components of the ETC (electron transport chain).

(e = electron)

e-donor in photosynthesis

H2O

QUIZ: Match the following components of the ETC (electron transport chain).

(e = electron)

e-acceptor in photosynthesis

NADP+ (to form NADH)