Rider Biology 1.9 — Chloroplasts & Photosynthesis
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118 Terms
What is a chloroplast?
A double-membraned organelle in plant cells that captures light energy and uses it to make carbohydrate fuel through photosynthesis.
Which cells contain chloroplasts?
Plant cells.
Do plant cells also contain mitochondria?
Yes.
What is the main job of a chloroplast?
To capture sunlight and convert that energy into stored chemical energy in carbohydrates.
What process occurs in chloroplasts?
Photosynthesis.
Why does Rider compare chloroplasts to solar-powered power plants?
They capture energy from sunlight and store it as chemical energy.
How many surrounding membranes does a chloroplast have?
Two.
What are the two surrounding chloroplast membranes called?
Outer membrane and inner membrane.
How is the chloroplast inner membrane different from the mitochondrial inner membrane?
It is not highly folded like the mitochondrial inner membrane.
Where does much of the important photosynthetic work occur?
In the thylakoids.
What is a thylakoid?
A flattened membrane disc inside a chloroplast.
What pigment is found in thylakoids?
Chlorophyll.
What is chlorophyll?
A light-absorbing pigment used in photosynthesis.
Why are chloroplasts green?
Because they contain chlorophyll.
What is a granum?
A stack of thylakoids.
What is the plural of granum?
Grana.
What is a lamella?
A membrane bridge connecting thylakoid stacks.
What is the stroma?
The fluid-filled region surrounding the thylakoids inside the chloroplast.
How does Rider describe the stroma?
The cytosol of the chloroplast.
What is the thylakoid lumen?
The space inside a thylakoid.
Where is the stroma relative to the thylakoids?
Outside the thylakoids but inside the chloroplast.
Where is the lumen?
Inside the thylakoid.
Using the pancake analogy, what is one pancake?
A thylakoid.
Using the pancake analogy, what is a stack of pancakes?
A granum.
Using the pancake analogy, what connects the stacks?
A lamella.
What does the chloroplast nucleoid contain?
Circular chloroplast DNA.
What shape is chloroplast DNA?
Circular.
Do chloroplasts have their own ribosomes?
Yes.
What do chloroplast ribosomes do?
They help make proteins.
What do starch granules store?
Carbohydrate nutrients.
What does chloroplast DNA encode according to Rider?
rRNAs, tRNAs, proteins for photosynthesis, and other essential components.
Are all chloroplast genes still inside the chloroplast?
No.
Where are many chloroplast genes located now?
In the cell nucleus.
What happens to proteins made from nuclear chloroplast-related genes?
They are transported into the chloroplast.
Can chloroplasts reproduce by division?
Yes.
What type of bacteria are chloroplasts thought to be related to?
Cyanobacteria.
What are cyanobacteria?
Bacteria that contain chlorophyll and perform photosynthesis.
What evidence supports the bacterial origin of chloroplasts?
They have circular DNA, ribosomes, double membranes, and reproduce by division.
What is the endosymbiotic idea for chloroplasts?
An ancient photosynthetic bacterium lived inside a larger host cell and eventually became a chloroplast.
What does photosynthesis convert sunlight into?
Stored chemical energy in carbohydrates.
What organelle later uses carbohydrate fuel made by chloroplasts?
Mitochondria.
What is the basic chloroplast-to-mitochondria pathway?
Sunlight → chloroplast → carbohydrate → mitochondrion → ATP.
What are the major stages of photosynthesis we studied?
Light reactions and sugar-building reactions.
Where do the light reactions occur?
In the thylakoids.
What do the light reactions require?
Light.
What molecule is split during the light reactions?
Water, H₂O.
What gas is released during the light reactions?
Oxygen, O₂.
Where does the oxygen released during photosynthesis come from?
Water.
What two useful energy molecules are made in the light reactions?
ATP and NADPH.
What is PSII?
Photosystem II.
What does PSII do?
It absorbs light and helps obtain energized electrons from water.
Which acts first, PSII or PSI?
PSII.
Why can the names PSI and PSII be confusing?
Photosystem II acts before Photosystem I in the pathway.
What happens to electrons after PSII?
They travel through electron-transfer proteins in the thylakoid membrane.
What happens to H⁺ during electron transport?
H⁺ accumulates inside the thylakoid lumen.
What is PSI?
Photosystem I.
What does PSI do?
It absorbs light and gives the electrons another energy boost.
What is the simple electron pathway?
Water → PSII → electron transport → PSI → NADPH.
What is NADPH?
An energy-rich electron carrier.
What is the main job of NADPH?
To carry high-energy electrons to sugar-building reactions.
What is a proton gradient?
A difference in H⁺ concentration across a membrane.
Where do many H⁺ ions accumulate?
Inside the thylakoid lumen.
What protein allows H⁺ to flow back across the thylakoid membrane?
ATP synthase.
What does ATP synthase make?
ATP.
What powers ATP synthase?
The flow of H⁺ down its gradient.
What is the simple chloroplast ATP-making sequence?
H⁺ gradient → ATP synthase → ATP.
How is chloroplast ATP production similar to mitochondrial ATP production?
Both use an H⁺ gradient and ATP synthase.
Where does the Calvin cycle occur?
In the stroma.
What three important inputs does the Calvin cycle use?
CO₂, ATP, and NADPH.
What provides the carbon atoms used to build carbohydrates?
Carbon dioxide, CO₂.
What is the main job of the Calvin cycle?
To use CO₂ and energy from ATP and NADPH to help build carbohydrates.
Where do ATP and NADPH used by the Calvin cycle come from?
The light reactions.
What is the relationship between the light reactions and the Calvin cycle?
Light reactions make ATP and NADPH; the Calvin cycle uses them to help build carbohydrate.
What does Rider call the reactions outside the thylakoids that do not directly require light?
Dark reactions.
Do dark reactions happen only at night?
No.
What half-sugar does Rider mention?
Glyceraldehyde, C₃H₆O₃.
What does Rider say is combined with CO₂ to make half-sugars?
Hydrogen produced through the photosynthetic pathway.
Where does Rider say the half-sugar is produced?
Outside the thylakoids in the chloroplast.
What happens to the half-sugars after they leave the chloroplast?
They are converted into glucose and other saccharides in the plant cell cytosol.
What is the formula for glucose?
C₆H₁₂O₆.
What are saccharides?
Sugars and carbohydrates.
What is the overall simplified photosynthesis pathway?
Light + water + carbon dioxide → carbohydrate + oxygen.
What three major things does a plant need for photosynthesis?
Light, water, and carbon dioxide.
Where does most water used by a plant come from?
The roots.
Where does most CO₂ used in photosynthesis come from?
The surrounding air.
How does CO₂ enter a leaf?
Through tiny openings called stomata.
What are stomata?
Tiny openings in leaves that allow gas exchange.
What is the pathway of CO₂ to the Calvin cycle?
Air → stomata → leaf tissue → chloroplast → stroma → Calvin cycle.
Can plant mitochondria also produce CO₂?
Yes.
What is the main external source of CO₂ for photosynthesis?
The atmosphere.
Which stage uses CO₂?
The Calvin cycle.
Which stage uses water and light?
The light reactions.
Which stage releases oxygen?
The light reactions.
Which stage makes ATP and NADPH?
The light reactions.
Which stage uses ATP and NADPH to help build carbohydrate?
The Calvin cycle.
Where is chlorophyll located?
In the thylakoid membrane.
Where is ATP synthase located?
In the thylakoid membrane.
Where is the Calvin cycle located relative to the thylakoids?
In the surrounding stroma.
A student says a granum is one thylakoid. Is that correct?
No. A granum is a stack of thylakoids.
A student says the lumen is the fluid around the thylakoids. Is that correct?
No. The lumen is inside a thylakoid; the stroma surrounds the thylakoids.