Plant Cells (Part One) Flashcards
What is a granum?
A stack of thylakoids
What does the stroma contain?
- Carbon-fixing enzymes
- Chloroplast DNA
- Ribosomes
What does the inner membrane contain?
- Chloroplast import machinery
- Chloroplast export machinery
What is contained in the thylakoid space?
- A light-capturing system
- ATP synthase
What percentage of sunlight that hits the leaf is absorbed by the plant?
~1%
What percentage of the energy absorbed by the plant is chemically bound?
28%
Give the main steps to the electron transport chain.
- Red light absorbed by chlorophyll, cleaving water to generate 1 oxygen, 4 protons and 4 electrons.
- The electron is transferred across the membrane which pumps 1 proton across the membrane.
- The electron is further excited in the photosystem I
- The electron is transferred onto NADP+ resulting in NADPH
- The proton gradient is utilised to generate ATP
Give the possibilities of where sugar ends up at the end of the Calvin cycle.
- Exported into the cytosol, where synthesised with fructose to make sucrose, or converted into pyruvic acid
which gets metabolised in mitochondria. - Maintained in stroma, where into starch that is stored in chloroplast and consumed at night.
Why are plants green?
Chlorophyll absorbs red and blue light, but green light is reflected.
How many proteins are encoded in the circular genome of chloroplasts?
~75
What percentage of the proteins required for photosynthesis are encoded in the plant nucleus?
90%
What three structures can proplastids become?
What are the functions of these structures?
- Chloroplasts (photosynthesis)
- Amyloplasts (starch storage)
- Chromoplasts (colouring)
Explain the steps to the colour change of leaves.
- Reduced photosynthesis, controlled by phytohormones.
- Cellular compartments degraded and recycled.
- Chloroplasts degrade into gerontoplasts.
- Breakdown products are stored in the plant vacuole.
- Anthocyanins are formed that protect against too much light and oxidative stress.
- Cells are killed, and recycled cellular components/molecules are released from the vacuole and delivered to the plant.
Name a pigment that absorbs yellow light.
Xanophylls
What stains the leaf yellow?
Carotinoide-containing chromoplasts become visible