Chapter 17 Energy For Biological Processes Flashcards
State how energy is used for biological processes
-Active transport
-Anabolic (building) and catabolic (breaking) reactions
-Movement of cilia, flagella or contractile filaments
-DNA replication, cell division and protein synthesis
What is an autotrophic organism?
Organisms which absorb light energy via photosynthesis to synthesis glucose by converting light energy into stored chemical energy.
What is a heterotrophic organism?
Organisms which obtain glucose through the consumption of other organisms.
Outline how respiration is used to release energy
Autotrophic and heterotrophic organisms break down organic molecules to release the energy needed for metabolic processes.
Outline how ATP is synthesised during photosynthesis
Light energy is used to form the chemical bonds in ATP, which then break to release the energy required to form glucose.
Outline how ATP is synthesised during respiration
Organic molecules like glucose are broken down to release the energy used to synthesise ATP.
Describe the structure of a chloroplast
-Double membrane bound known as the chloroplast envelope
-Thylakoids are fluid- filled sacs which stack to form Grana
-Grana are linked by thylakoid membranes known as lamellae
-Fluid filled interior known as the stroma containing enzymes, sugars and organic acids.
-Photosystems are composed of the light harvesting system and reaction centre which contain photosynthetic pigments attached to proteins and are used by plants to absorb light energy.
-Starch grains in stroma
-Circular DNA in the stroma
What are reaction centres of chloroplasts?
Photosystems which contain primary photosynthetic pigments which absorb light energy for the light dependent reaction.
What are light harvesting systems of chloroplasts?
Photosystems containing accessory pigments embedded within the thylakoid membrane. They surround reaction centres and transfer light energy to them to increase energy availability for excited electrons.
State the primary pigment within the reaction centre of Photosystems
Chlorophyll A which absorbs red and blue light and reflects green
State the accessory pigments within the light harvesting systems of Photosystems
Chlorophyll B
Carotenoid
Xanthophyllis
State the difference between Photosystems I and II
Photosystem I absorbs light at a higher wavelength - 700nm
Photosystem II absorbs light at a lower wavelength - 680nm and contains the enzyme which catalyses the splitting of water molecules via hydrolysis
State the two stages of photosynthesis
Light dependent stage
Light independent stage
What is the light dependent stage of photosynthesis?
Energy from sunlight is absorbed and used to form ATP
Hydrogen from water is used to reduced coenzyme NADP into reduced NADP
Where does the light dependent stage take place?
Thylakoid membrane
What is the light independent stage of photosynthesis?
Hydrogen from reduced NADP and Carbon dioxide is used to build organic molecules
Energy for this is provided via ATP from the light dependent stage
Where does the light independent stage take place?
Stroma
Describe the process of the light dependent stage of photosynthesis
-Light energy is absorbed by Photosystem II and excites electrons at the reaction centre
-Excited electrons are released from the reaction centre and move to a higher energy level where they are passed onto an Electron transport chain to Photosystem I
-The electrons lost from the reaction centre of Photosystem II are replaced by the photolysis of water. H2O —> 1/2 O2 + 2e- + 2H+
-The electrons move down the electron transport chain via electron carriers, losing energy
-The energy that is released is used to allow H+ ions into the thylakoid via proton pumps so the thylakoid then has a higher concentration of protons than stroma.
-The protons move back down the concentration gradient via channel proteins, the movement activates ATP synthase to catalyse to reaction of ADP and Pi to form ATP by phosphorylation- the overall process is known as chemiosmosis
-Light energy is then absorbed by the Photosystem I which excites electrons to a higher energy level so chemiosmosis can occur again
-The electrons leaving the electron transport chain following Photosystem I are accepted alongside and electron by co enzyme NADP forming reduced NADP.
-This reduced NADP and the ATP formed is used during the light independent stage.
What is non- cyclic photophosphorylation?
The synthesis of ATP and reduced NADP using Photosystem I and II.
What is cyclic photo phosphorylation?
Synthesis of ATP involving Photosystem I only as the electrons are not passed onto NADP, but are passed back to Photosystem I via electron carriers to produce small amounts of ATP.
