EXAM 4 Flashcards
Autotrophs
- self-feeding plants
- Algae, plants, some prokaryotes
- Usually photosynthetic but doesn’t have to be (chemotrophs)
- Organisms that use carbon from simple substances to make organic compounds
Heterotrophs
- Other-feeding plants
- Animals, fungi, some prokaryotes and protists
- Usually also get energy from organic compounds
- Organisms that use carbon from organic sources to make organic compounds
Systems of the Plant: Shoot System
Outgrowth that originates from the plumule of the seed’s embryo above the ground; can be interchanged with the word stem
-stem
-leaves
-reproductive organs
Systems of the Plant: Root System
Everything that is underground in the plant
- roots
Where does photosynthesis occur?
Photosynthesis occurs in certain organelles in specialized cells in the plant
Anatomy of the Leaf: Cuticle
- Non-cellular protective layer
- Waterproof - prevents water loss
- Typically very large because they need a large surface area for photosynthesis
- A waxy layer - this prevents air from getting in and out
Anatomy of the Leaf: Epidermis
- Cells that make the cuticle
- Protects the skin
Anatomy of the Leaf: Mesophyll
Middle of the leaf where photosynthesis takes place
- Spongy: more circular cells, less tightly packed; doing less photosynthesis (layer closer to the bottom of the leaf, this arrangement is to allow CO2 to spread easily throughout the leaf)
Anatomy of the Leaf: Palisade in the Mesophyll
Made up of these long, tightly packed cells; it is a wall of vertical tree trucks (what the cells look like)
- Have a columnar arrangement that maximizes light interception
Anatomy of the Leaf: Stoma
Mouth/opening of the leaf
- Holes that allows air in and out
Anatomy of the Leaf: Guard Cells within the Stoma
On either side of the opening
1. They can open and close without having muscles
2. They have pumps that will pump solute into the cell and channels that will allow solute to leave the cell
3. When K+ is pumped into the guard cells, its going to increase the osmotic pressure inside the cell and water is going to flow into the cell
4. There are microfibrils that are arranged around the water that goes into the cell, it causes an opening which is the stoma
Anatomy of the Leaf: Vascular Tissue
- In leaf, stem, and root
- Usually non-photosynthetic
- Specialize in transport
- Xylem and Phloem flowing through
- Likely located in the spaces between spongy mesophyll layer
C3 Plants
C3 plants open stomata during the day to allow CO2 in while the plant is doing photosynthesis
- High water loss during the day
CAM Plants
Open stomata at night and then close them during the day (cacti)
- Stores CO2 as other organic compounds
- Requires energy to use it
- Reduces the water loss
Where does dry weight in photosynthesis come from?
Dry weight comes from air
How does photosynthesis compare to cellular respiration?
Cellular respiration is the opposite of photosynthesis
What are the two parts of photosynthesis?
Light Reactions and Calvin Cycle
Light Reactions
“photo” portion of photosynthesis “light”
- Makes ATP, NADPH, and releases O2
Calvin Cycle
“synthesis” portion of photosynthesis “making”
- Takes in CO2 and makes sugars
How is photosynthesis similar to cell respiration?
The first 3 steps where it takes sugars and makes CO2 and NADPH
Chloroplasts
An organelle known as a plastid that is characterized by its two membranes
- These store chlorophyll, which is a green pigment (an inner and outer membrane)
Thylakoids
Flattened sacs in the inner membrane of the chloroplasts
1. Where the light-dependent reactions occur by absorbing light
2. Inside the thylakoid is the thylakoid lumen
Granum
Stacks of thylakoids within the chloroplasts
- Used to increase surface area for more absorption of sunlight
Stroma
Liquid matrix of chloroplasts
- This is the enzyme-rich fluid that is contained inside the chloroplast
- This is the site of light-independent reactions
Endosymbiont Theory of Chloroplasts
- Chloroplasts once were bacteria
- Chloroplasts have their own DNA and ribsomes
Input of Light Reactions within Photosynthesis
Sunlight, NADP+, ADP, H2O
Output of Light Reactions within Photosynthesis
ATP, NADPH, O2
Two Interconnected Systems of Light Reactions
Make ATP, make NADPH, then use both of these to make sugars in the Calvin Cycle
Chlorophyll
- This is the start of photosynthesis
- Reflects green light
- The Photosynthetic Complex (Antenna Complex)
Antenna Complex within Chlorophyll
When chlorophyll molecules absorbs light energy, their electrons jump to an excited state and transfer energy to the RCC which donates an electron to start the electron transport chain
1. Located within the thylakoid membrane
2. Site of light absorption
3. Large protein complex that contains:
- Lots of chlorophyll molecules
- A single Reaction Center Chlorophyll (RCC)
Reaction Center Chlorophyll
Specialized chlorophyll that loses its electron
1. Performs the light-dependent reactions of photosynthesis
Absorbance of Chlorophyll
- The least important color involved in photosynthesis is green
- Absorbs mainly red and violet
- This requires magnesium
- Accessory pigments - aids photosynthesis by absorbing light that chlorophyll cannot
Photolysis
Splitting water
- Reaction Center Chlorophyll left without an electron
- Steals an electron from water
a. O2 evolving complex
- Water is left without an electron
a. Oxidized
b. Water is split into H+ ions plus O-
c. O- combines with another O- to make O2
- O2 given off as waste gas
Photosystem 2 makes H+ Gradient
- Makes H+ from H2O
- Electron Transport Chain similar to in the mitochondria
- H+ is pumped from the stroma to the lumen of the thylakoid along with the electron from the RCC
- ATP synthase uses H+ gradient to make ATP as it goes down the ETC
Photosystem 1 makes
NADPH along with ATP
3 Steps of the Calvin Cycle
- Fixation: Adds CO2 to Carbon molecule
- Takes CO2 and adds it to a 5 carbon molecule
- Breaks into two and results in two of the same 3 carbons molecules (3-PGA) - Reduction: 3-PGA reduced to glyceraldehyde-3-phosphate
- Reduces ATP and NADPH
- Produces ADP and NADP+
- Produces 1 G3P molecule
- The Calvin Cycle has to repeat 6 times while allows
for 12 G3P - Regenerate: RuBP
- Requires more ATP
- Then 2 of them are used to make glucose and the
other 10 are used to regenerate the 5 Carbon starting product used in the cycle
Carbon Fixation
- RuBP aka Ribulose Biphosphate is a 5 carbon molecule
a. CO2 enters the chloroplast from the environment - CO2 combines with RuBP to form a 6 carbon molecule (this is unstable and does not last very long bc it breaks down)
a. Ribulose-Biphosphate Carboxylase-Oxygenase (RuBisCO) is an enzyme used to combine the RuBP and CO2; unstable intermediate falls apart - Forms 2 3-carbon molecules called 3-PGA
- RuBisCo Alternatives:
a. Carboxylase: adds CO2 to RuBP (good)
b. Oxygenase: adds O2 to RuBP (bad)
Reduction
- Carbon Input: 3PGA
a. The 3PGA is then phosphorylated (gains phosphate from ATP)
b. This creates PGA-P
c. Then each PGAP is reduced by accepting an electron and a proton from NADPH
d. This creates G3P - Carbon Output: G3P
a. One G3P out of every 6 is removed from the Calvin Cycle to help produce Glucose
b. The remainder (5 groups) of G3P is used to regenerate RuBP
Regeneration
- Rearrange 5 of the 3 carbon G3P molecules into 3 of the 5 carbon RuBP
- Requires more ATP
Sugar Synthesis
- G3P from Calvin Cycle is used
- 3-carbon building blocks are used to make sugars (glucose)
- Similar to glycolysis but backwards
- Requires NADPH and ATP
- Occurs in cytoplasm
Photorespiration
- C3 Photosynthesis
a. Normal Photosynthesis
b. Named for 3-PGA, first product of fixation, C3 - Photorespiration
a. RuBisCo takes O2 instead of CO2; regenerate RuBP
b. Happens more when stomata are closed because it is hot
c. This creates 2-PG (which is a 2 carbon molecule along with a 3 carbon PGA)
d. Requires ATP to redo the process
C4 Photosynthesis
- Bundle sheath cells arranged around vascular tissue (the area where photosynthesis takes place in the C4 plants which keeps the O2 out)
- There are however passageways within the sheath that allow CO2 through so that photosynthesis may occur
- Bundle sheath cells insulated from air by mesophyll cells
- Only mesophyll cells come into contact with air
The Process of C4 Photosynthesis
- CO2 captured by PEP carboxylase and combines with PEP (3 carbon molecule to form a 4 carbon molecule that then forms into another 4 carbon molecule) Then CO2 is produced and pyruvate is a byproduct
- This all occurs within the Bundle Sheath cells
- CO2 then enters Calvin Cycle and makes sugars
- Requires extra ATP
CAM Photosynthesis
Best for avoiding the most water loss
1. Night:
a. Stomata open- so that there is less water loss due to the heat
b. Stores CO2 that is brought in and as C4 acid in vacuoles
2. Day:
a. Light reactions
b. Stomata closed
c. The acid that is storing the CO2 is converted back to just CO2
d. Releases CO2 into the Calvin Cycle which goes to RuBisCo etc.
Xylem: Zombie Plants
Experiment in 1890
1. Cut root off plant and put in poison
2. Plant dies but anatomy stays intact
3. Put roots in water
4. Plant continues to draw up water for days
Xylem: The Stem
Vascular Plants, Angiosperms, and Gymnosperms
1. Epidermis: cover and protect
2. Ground Tissue: support and filler; these have the stiffening molecules that keep the plant upright
3. Vascular Tissue:
a. Different arrangements of vascular tissue in different lineages but always together
b. Xylem: transports water and minerals from roots to leaves
c. Phloem: Transports sugar proteins and hormones
