C1 Flashcards
True or False
Diffusion and osmosis are forms of active transport
False
True for False
Xylem in plant cells transports water to different parts of plants
True
True or False
Humans produce oxygen through cellular respiration
False
True or False
Chlorophyll is the only pigment in plant cell
False
Photosynthesis
A process that converts solar energy into chemical energy
6 CO2 + 6 H2O → C6H12O6 + 6 O2
___ energy is the ultimate source of energy for mostliving things
Solar energy
Organisms use energy indirectly from _____ organisms at first trophic levels
Photosynthetic
As our populations grow, rates of ____ grow, and we become ______ dependent on photosynthesis
- Consumption
- More
What does light travel in
Waves called photons (small units of energy)
Short vs. Long wavelenghts
- Short wavelenghts have high energy
- Long wavelenghts have low energy
What type of radiation is light
Electromagnetic
Includes X-rays, radiowaves
What colors is visible light composed of
White light is a mixture of all visible light/colors
What wavelenght is light from the sun
Light from the sun is a mixture of different wavelenghts
What energy is required for photosynthesis
Light energy
Chlorophyll
- Green coloured pigment
- Found in plants, algae, protists, cyanobacteria
- Absorbs photons and begins photosynthesis
Different types of Chlorophyll found in photosynthetic organisms
- Chlorophyll-A (blue-green) is the primary light absorbing pigment
- Chlorophyll-A and B absorb photons with energies in the blue-violet and red regions of the spectrum and reflect/transmit those wavelenghts
Accessory Pigments
- Chlorphyll B (yellow-green)
- Carotenoid (orange)
Role of accessory pigments
Accessory pigments abosrb other photon wavelenghts and pass the energy to chlorophyll A
Spectrophotometer
Can determine the absorption spectrum of pigments, shows which pigments absorb which wavelenghts of colors
Chromatography
Technique used to seperate pigments
- Pigments dissolved in fluid
- Fluid passes through material
- Pigments move at different speeds (distances)
Chloroplast Structure
Stroma
Gel-like enzyme-rich substance filling chloroplast
Protein-rich semilquid material. This is where chemical reactions and synthesis of carbs occurs
Chloroplast Structure
Thylakoids
A system of membrane-bound sacs that stack on top of each other to form columns
Plant cell requirements to undergo photosynthesis
- Chlorophyll
- Be able to obtain CO2 and H2O
- Be able to capture solar energy from the environment
Chloroplast Structure
Membranes
2 limiting membranes: Inner and Outer
Chloroplast Structure
Grana Stacks
- Stacks of thylakoid discs
- One chloroplast may have 60 grana; each containing 30-50 thylakoids
Lamellae
Unstacked thylakoids that connect adjacent grana
Chloroplast Structure
Thylakoid Membrane
Contains light gathering pigment molecules and other molecules and complexes essential to the process.
Enclose an interior (water filled) thylakoid space
Chloroplast Structure
Lumen
A fluid-filled space inside thylakoid
Leaf Structure
Where are chloroplasts found
In the palisade mesophyll
Leaf Structure
How does sunlight reach the palisade mesophyll layer
Sun passes through waxy cuticle, through the upper epidermis into the palisade mesophyll layer
Leaf Structure
Palisade Tissue Cells
- Long, narrow cells packed with chloroplasts.
- Under the uppper surface of the leaf
- Where most photosynthesis occurs in the leaf
Leaf Structure
Vascular Tissue Cells
- Xylem tubes carry water and minerals from the roots to the leaves
- Phloem tubes carry sugars to various parts of the plant
Leaf Structure
Spongy Tissue Cells
- Round and more loosely packed than palisade cells, with many air spaces between them
- These cells have chloroplasts so they perform some photosynthesis
- Their structure helps the cells to exchange gasses and water with the environment
Leaf Structure
Stomata
- Small opening in the outer (epidermal) layer that allow CO2 into the leaf and O2 out of the leaf
- H2O also diffuses out of the leaf through stomata
Products of Photosynthesis
ATP
- High energy molecule used by all living cells
- Provides an immediate source of energy for cellular processes
- Formed by addition of ADP and Pi
ADP
- A molecule containing 2 high-energy phosphate bonds that may be formed by breaking one of the phosphate bonds in ATP
- ADP + Pi + Energy → ATP
- Energy comes from the chemical potential energy in the bonds of glucose molecules during cell resp.
Products of Photosynthesis
NADPH
- During photosynthesis NADP+ accepts 1 H atom and 2 e- to form NADPH
- NADPH is an electron donor, thus it becomes NADP+ again
- Involved in energy transfers
Products of Photosynthesis
Glucose
- Transport Molecule (blood sugar)
- Medium-term energy storage (bonds)
Light dependent reactions
- Directly energized by light
- Require chlorophyll
- Occur in thylakoid membrane
Stages of Photosynthesis
Light independent reaction (dark reaction)
Calvin Cycle
Light-Dependent Reactions
Photosystems
Membrane proteins; cluster of photosynthetic pigments responsible for capturing light
Photosystems are named in the order they were discovered. Photosystem I was discovered first but actually comes second in this process
Light-Dependent Reaction
Reduction + Oxidation Reaction
LEO the lion goes GER
- Lose Electrons → Oxidation
- Gain Electrons → Reduction
Occurs with NADP+ and NADPH
When electrons transfer between two substances, both oxidation and reduction reactions occur simultaneously
What type of reaction is photosynthesis
Photosynthesis is a redox reaction
- CO2 & C6H12O6 is reduced
- H2O & O2 is oxidized
Light-Dependent Reaction
Step 1
Photo-excitation:
1. Photon from the sun strikes a molecule of chlorophyll inside of PS II (wavelenght of 680)
2. That electron absorbs the energy from the photons and gets excited (low energy to high energy due to the photon)
3. It leaves photosystem II to travel down the ETC towards PS I
The missing electron will be replaced by step 3
Light-Dependent Reaction
ETC
A series of progressively stronger electron acceptors; each time an electron is transferred energy is released
Light-Dependent Reaction
Step 2
ETC (PS II → PS I):
* Electrons move through the proteins in the ETC
* As it moves through the ETC, the electron releases energy (decreased potential energy)
* The chain uses energy released from the electron to bring hydrogen ions into thylakoid
Occurs at the same time as step 3
Light-Dependent Reaction
Step 3
Photolysis:
* Occurs within the thylakoid
* Water is split into Hydrogen, Oxygen and an electron
* 2 H2O + solar energy → 4 H+ + 4 e- + O2
* Oxygen: released from leaf back into air
* Hydrogen: continue to build up hydrogen ions in the thylakoid
* Electron: replaces the missing electron from PS II
Occurs simultaneously with step 2
Light-Dependent Reaction
Step 4
Chemiosmosis:
- Hydrogen is pumped into thylakoid lumen and the resulting energy helps generate ATP through a REDOX reaction
- ATP Synthase Complexes: Protein complexe embedded in thylakoid membrane that allows H+ ions to escape from lumen and uses the resulting energy to generate ATP
Light-Dependent Reaction
Step 5
Reduction ADP → ATP:
* Once the hydrogen ions pass through ATP synthase a reduction reaction occurs
Light-Dependent Reaction
Step 6
ETC (PS I → Stroma):
* Occurs within the thylakoid membrane
* Electron absorbs the energy from the photons (photoexcitation)
* Once it absorbs a lot of energy, it leaves PS I to head towards the stroma
Light-Dependent Reaction
Step 7
Reduction NADP+ → NADPH:
- NADP+ + H+ + 2e- → NADPH → Calvin Cycle
- NADP+ is reduced
- NADPH is oxidized
- NADPH had reducing power because it can donate an electron
4 Main Steps in ETC
- e- from PS II are transferred along an ETC and across the thylakoid membrane to inner surface
- Some of their energy is uised to pull H+ ions across the membrane = positive charge building in lumen
- e- that have lost lots of original energy are transferred to chlorophyll molecules in PS I where they absorb energy again and reach excited state
- High-energy e- from PS I are transferred to NADP+ to form NADPH
Light Independent
Calvin Cycle
- Does not require en energy from photons
- Occurs in the stroma (empty space in chloroplast)
- Mechanism: Carbon fixation - forms high-energy organic molecules from CO2
Calvin Cycle
Step 1
Carbon Fixation:
* Inorganic carbon is turned converted into organic compounds (carbs)
- CO2 + RuBP → 6 Carbon Molecule → 3-PGA + 3-PGA
- CO2 + RuBP → 6 Carbon Molecule → 3-PGA + 3-PGA
- CO2 + RuBP → 6 Carbon Molecule → 3-PGA + 3-PGA
An ezyme called rubisco is required in order to make this reaction happen
- 6 carbon molecule is unstable and breaks into 2 3-PGA molecules immediately
Calvin Cycle
Step 2
Activation and Reduction:
- Requires 6 NADPH and 6 ATP molecules (from light dependent reaction)
- 3-PGA + ATP → active 3-PGA + NADPH → G3P
- 3-PGA + ATP → active 3-PGA + NADPH → G3P
- 3-PGA + ATP → active 3-PGA + NADPH → G3P
- 3-PGA + ATP → active 3-PGA + NADPH → G3P
- 3-PGA + ATP → active 3-PGA + NADPH → G3P
- 3-PGA + ATP → active 3-PGA + NADPH → G3P
ATP “activates” 3-PGA and NADPH donates electrons to or reduces, a three-carbon immediate to make G3P
Calvin Cycle
Step 3
Replacement of RuBp:
* Requires 5 G3P molescules; 3 ATP (9 total now)
* Production: regenerates RuBP molecules; makes ½ glucose molecule
- ATP activates 3-PGA
- G3P is the building block of glucose; it is still a 3 carbon compound
Calvin Cycle
Molecules Used
- 3 ATP and 2 NADPH consumed for every 1 CO2 that enters
- 18 ATP and 12 NADPH produces 1 glucose
- 6 H2O consumed for every glucose formed
Where does the Calvin Cycle occur
In the stroma of the chloroplast
How does CO2 enter plant leaf cells
CO2 doffises directly into the photosynthesizing plant leaf cells and chloroplasts from air spaces within the leaves
The air spaces are connected to the outside environment via tiny openings in the surface of the leaves
Effect of temperature on Rubisco
IB
- Rubisco (enzyme) has an optimal temperature
- Increasing temp. increase the likelihood of a collision between Rubisco, RuBP and CO2 until the enzyme denatures because temp. is too high
- Optimal temp. is at which photosynthesis rate is at its fastest
Effect of light intensity on chlorophyll
IB
- As light intensity increases, more chlorophyll becomes photo-activated until all of it is activated in which photosynthetic rate will plateau
- This is because there are a limited number of chlorophyll molecules
