CHAPTER 17 - ENERGY FOR BIOLOGICAL PROCESSES Flashcards
1
Q
What examples of metabolic activities require energy
A
Active transport - (Essential for the uptake of nitrates by root hair cells, loading sucrose into sieve tube cells, selective reabsorption of glucose and amino acids in the kidney and the conduction of nerve impulses)
Anabolic Reactions - (Building of polymers such as Proteins, Polysaccharides and nucleic acids essential for growth and repair)
Movement - (brought about by cilia, flagella or the contractile filaments in muscle cells)
2
Q
What are the flows of energy through living organisms
A
pg 460
3
Q
How do plants make use of energy in glucose molecules
A
Photosynthesis, glucose formed,
light is trapped by chlorophyll molecules, which is used to drive the synthesis of glucose from CO2 and Water
4
Q
What is Respiration
A
The process which organic molecules, such as glucose, are broken down into smaller into smaller inorganic molecules like carbon dioxide and water
5
Q
Where is the energy stored within the bonds of organic molecules
A
Within the bonds of organic molecules that synthesise ATP (Adenosine triphosphate)
6
Q
What are the two most important reactions in the living world
A
Photosynthesis (produces most of the biomass on earth) and Respiration (breakdown of the biomass to provide ATP for reactions)
7
Q
What is the equation and purpose of Photosynthesis
A
6CO2 + 6H2O <—> C6H12O6 + 6O2
Trap energy
8
Q
What is the equation and purpose of Respiration
A
C6H12O6 + 6O2 —–> 6CO2 +6H2O
Release energy
9
Q
How is energy used in regard to bond breaking and forming
A
Energy is used to break bonds
Energy is released to form bonds
10
Q
What is an exothermic reaction
A
Releasing of energy, heat to surroundings, more energy needed to form bonds than break them
11
Q
What is an endothermic reaction
A
Takes in energy, heat to surroundings, more energy needed to break bonds than form them
12
Q
Explain why it is incorrect to say that energy is produced
A
Energy cannot be created (or destroyed) energy is transferred
ATP is produced
13
Q
Explain why ATP is not a good energy storage molecule but why organic molecules like lipids or carbohydrates are
A
ATP is not very stable easy to remove phosphate group
organic molecules are (more) stable
organic molecules are more energy dense
14
Q
Explain the interrelationship between respiration and photosynthesis in organisms
A
In photosynthesis light energy is converted into chemical energy
inorganic molecules are
converted into organic molecules
water and carbon dioxide are converted to glucose (and oxygen)
Respiration uses oxygen produced in photosynthesis
organic molecules are broken
down into inorganic molecules
energy released is used to synthesise ATP
carbon dioxide
produced is used in respiration
15
Q
What is broken down in respiration to form small inorganic molecules
A
Large organic molecules (eg. glucose)
16
Q
Is respiration endo- or exothermic and why
A
Exothermic
Total energy required to break all of the bonds in a complex organic molecule Is less than the total energy released in the formation of all the bonds in the smaller inorganic products
17
Q
What is the excess energy released during the formation of bonds in respiration used for
A
Synthesising ATP
18
Q
What polarity of bond forms between Carbon and hydrogen
A
Non-polar, which means they are weak, and not a lot of energy is required to break them
19
Q
Where does the extra energy required to make large molecules from small inorganic molecules in photosynthesis come from
A
The Sun
20
Q
Why does respiration release large quantities of energy
A
The carbon and hydrogen released from large molecule form strong bonds with oxygen atoms, forming water and carbon dioxide - less energy needed to break bonds than form them
21
Q
How is ATP produced in photosynthesis and respiration primarily synthesised
A
Chemiosmosis
22
Q
What is Chemiosmosis
A
The diffusion of protons from a region of high concentration to a region of low concentration through a partially permeable membrane
23
Q
How does the movement of protons in chemiosmosis synthesise ATP
A
Movement of protons down their concentration gradient releases energy that is used in the attachment of an inorganic Phosphate (Pi) to ADP, Forming ATP
24
Q
What is Chemiosmosis dependant on
A
The creation of a proton concentration gradient
25
Where does the energy needed to create a proton concentration gradient come from
High energy electrons - Excited electrons
26
How are Electrons raised to higher energy levels, or excited?
Electrons present in pigment molecules (eg. chlorophyll) are excited by absorbing light from the sun
High energy electrons are released when chemical bonds are broken in respiratory substrate molecules (eg. glucose)
27
Where do Excited electrons pass into after the have been raised to higher energy levels
Electron transport chain to generate a proton gradient
28
What is the electron transport chain made up of
A series of electron carriers, each with progressively lower energy levels
(pg 464)
29
How is a concentration difference maintained
As High energy electrons move from one carrier to another, energy is released, which is used to pump protons across a membrane
Proton gradient is maintained as the membrane is still impermeable to Hydrogen ions
(pg 464)
30
What is the only way Hydrogen ions (protons) can move back through the membrane
Hydrophilic membrane channels linked to the enzyme ATP synthase (catalyses formation of ATP from ADP and Pi)
(pg 464)
31
Explain the importance of ATP to living organisms
Universal energy currency
energy transfer is, quick/immediate
energy is in, small/usable,
quantities
(energy transfer) is quick, (energy transfer) in quantities that can be used; ATP can be
resynthesised
32
Describe the properties of cell membranes necessary for the formation of a proton gradient
Impermeable to, ions/protons
idea that there can be different concentrations of protons on each
side of a membrane
contains, embedded / integral, proteins
e.g., ATP synthase enzyme
responsible for synthesis of ATP
33
Name the type of diffusion which enables protons to move through ATP Synthase and explain the role of ATP synthase in the production of ATP
Facilitated diffusion
ATP synthase provides hydrophilic channel for diffusion of protons
catalyses the synthesis of ATP
lowers activation energy
34
The Synthesis and breakdown of ATP is an example of a reversible reaction
ADP + Pi <----> ATP
ATPase is often the name given to the enzyme which hydrolyses ATP, producing ADP and Pi. ATPase and ATP Synthase are, in fact, the same enzyme. Explain how this is possible
Reversible reaction
the products formed from reaction in one direction are the
substrates of reaction in reverse direction (1);
active site is complementary to both substrates and
products
so substrates and products can bind to same active site
direction of reaction
depends on relative concentrations (of substrates/products) on either side of reaction
35
What are Autotrophic organisms
Organisms that can make their own food, mostly through photosynthesis
eg. plants and algae
36
What are Heterotrophic organisms
Organisms that obtain their food from eating other organisms
37
What is the equation for photosynthesis
6CO2 + 6H2O ---> C6H12O6 + 6O2
38
What do the network of membranes provide in a chloroplast
Large surface area (to maximise absorption of light essential to first step of photosynthesis)
39
Where does photosynthesis take place
Chloroplasts
40
What is a Thylakoid
The flattened sacs in a chloroplast
41
What is a Granum (pl. Grana)
Stacks of Thylakoids
42
What are the membraneous channels Grana are joined together by
Lamellae
43
Which part of the chloroplast is the pigment Chlorophyll (and other pigments) located
Embedded in thylakoid membranes
44
What is the fluid enclosed within a chloroplast
Stroma
45
What do pigment molecules do
Absorb specific wavelengths (colours) of light and reflect others
Different pigments absorb and reflect different wavelengths
46
What is the primary pigment in photosynthesis
Chlorophyll A
47
What colours does chlorophyll absorb and reflect
Absorbs red and blue
Reflects green
48
What are some other pigments involved in photosynthesis
Chlorophyll b, Xanthophylls and Carotenoids - gives different shades and colours of leaves
49
What is the light harvesting system (antennae complex)
A combination of photosynthetic pigments and other proteins
50
What is the role of the Light harvesting (antennae complex)
To absorb, or harvest, light energy of different wavelengths and transfer this energy quickly and efficiently to the reaction centre
51
What pigment is present in the reaction centre
Chlorophyll A
52
What are the 2 different types of pigment in photosystems
Primary and accessory pigments
(pg 468)
53
What colour are carotene and Xanthophyll
Orange
Yellow
54
What happens to chlorophyll if sunlight is too intense
Chlorophyll is destroyed
55
What is Anthocyanin
Red/purple pigment, formed from a reaction between sugars and proteins in cell sap
56
When is Anthocyanin produced
When concentration of sugars is high
High light intensity also promotes production of Anthocyanin
More light = more Photosynthesis, makes sugar
More sugar = more Anthocyanin
57
What is the role of Anthocyanins
Sunscreen, absorbing blue-green and Ultraviolet light, inhibiting destruction of Chlorophyll
58
What determines the colour of Anthocyanins
pH - red to purple scale
Red in apples
Purple in black grapes
59
Suggest explanations for the following observations
a) Apples are often red on one side and green on the other
b) Leaves with more vibrant red colours are seen during years when there has been lots of sunlight and dry weather. When it has been raining and overcast there will not be as much red foliage present
A) Anthocyanins are red pigment
produced when light intensity and sugar concentration is high
apples have high sugar concentration; high intensity light affects one side more than the other.
B)Produced by enzymes
enzyme activity is temperature dependent
60
Suggest why the production of anthocyanin is temperature-dependent
Enzymes involved in metabolic pathway
3D shape of enzyme is different at different temperatures
shape of active site changes
enzymes activated/inactivated
61
What can be used to identify photosynthetic pigments
Chromatography
62
How do you calculate Rf value
Distance travelled by solute / Distance travelled by solvent
63
What are the two stages of photosynthesis
Light-dependant and Light-independent
64
What happens in the light-dependent stage
Energy from sunlight is absorbed and used to form ATP
Hydrogen from water is used to reduce coenzyme NADP to form reduced NADP
(pg 469)
65
What happens in the light-independent stage
Hydrogen from reduced NADP and Carbon dioxide is used to build organic molecules, such as glucose
ATP supplies required energy
(pg 469)
66
What is the order to the two photosystems involved in the non-cyclic photophosphorylation stage of the light dependant-stage
Photosystem II (PSII) followed by Photosystem I (PSI)
67
Which of the photosystems absorbs higher wavelength, PSI or PSII
PSI (700nm) (PSII absorbs 680nm)
68
Where does electron excitation occur
Reaction centres of photosystems
69
Describe the events in non-cyclic photophosphorylation
Suns (light/UV) energy excites electrons at reaction centre in PSII
Excited electrons are released from reaction centre of PSII and passed to electron transport chain
ATP is produced in chemiosmosis
The electrons lost at PSII reaction centre are replaced by photolysis
Excited electrons are released from reaction centre at PSI and passed onto another electron transport chain
ATP is produced by chemiosmosis
Electrons lost at PSI reaction centre are replaced by electrons passed along the ETC after being released from PSII
Electrons leaving PSI are accepted, along with a hydrogen ion, by coenzyme NADP to form Reduce NADP
NADP provides hydrogen or the reducing power in the production of organic molecules, eg. glucose, in the light independent stage
(pg 470)
70
What is photolysis
The splitting of water molecules into Hydrogen ions, electrons and oxygen molecules using energy from the sun
71
What is the equation of photolysis
H2O ---> 1/2 O2 + 2e- + 2H+
72
What does the oxygen-evolving complex in PSII do
it is an enzyme that catalyses the breakdown of water
73
Where do each of the products of Photolysis go
Electrons (2e-) - go to electron deficient PSII
Hydrogen (2H+) - Released into Lumen of thylakoids, increasing proton concentration across the membrane, moving down a concentration and electrochemical gradient driving the formation of ATP, then return to storm combining with NADP to form reduced NADP with an electron from PSI
Oxygen gas (1/2 O2) - Released as by-product
(pg 470)
74
Describe cyclic-photophosphorylation
Electrons leaving the Electron transport chain after PSI can be returned to PSI, instead of being used to form Reduced NADP, leading to Cyclic photophosphorylation
PSI can still produce ATP without any electrons being supplied from PSII
Reduced NADP is not produced when this process occurs
(pg 471)
75
What are the 3 stages that take place in light-dependant stage of photosynthesis
Non-cyclic photophosphorylation
Cyclic photophosphorylation
Photolysis
76
What are the two stages in the light-independent stage of photosynthesis
Calvin Cycle
Regeneration of RuBP (Ribulose Bisphosphate)
77
Where does the Light dependant stage take place
Thylakoid membranes (maybe)
78
Where does the light independent stage take place
Stroma (fluid enclosed within a chloroplast)
79
What is the raw material used in the Light-independant stage of photosynthesis
Carbon Dioxide (ATP and reduced NADP are also required, and produced from Light dependent stage)
80
Describe the events in the Calvin Cycle
FIXATION:
Carbon dioxide enters the intracellular spaces within spongy mesophyll by diffusion through stomata
Diffuses into cells and into stroma of chloroplasts where it combines with 5C molecule - Ribulose Bisphosphate (RuBP)
Carbon in Carbon dioxide is therefore fixed, now incorporated into an organic molecule
REDUCTION:
The enzyme Ribulose Bisphosphate Carboxylase (RuBisCo) catalyses reaction and unstable 6C intermediate is produced
(RuBisCo is inhibited by oxygen)
Unstable 6C compound immediately breaks down into 2x 3C Glycerate 3-phosphate (GP) molecules
Each GP molecule is converted into Triose Phosphate (TP) using Hydrogen atom released from reduced NADP and energy from ATP (both from light dependent stage)
(leaves 2 TP molecules)
REGENERATION
Most of TP is recycled to regenerate RuBP so Calvin cycle can continue, the rest is sued as a starting point to synthesise Carbohydrates (glucose mostly), Lipids, Proteins and amino acids
(pg471)
81
What are the 3 summarised steps of the Calvin cycle
Fixation: CO2 is fixed (incorporated into RuBP)
Reduction: GP is reduced to TP by addition of H atom from reduced NADP using Energy supplied by ATP
Regeneration: RuBP is regenerated from the recycled TP
82
How is RuBP regenerated
Each turn of Calvin Cycle produces 2 TP molecules
For one glucose molecule to be produced, 6 CO2 molecules will have to enter Calvin cycle, so 6 full turns of cycle
Overall production - 12 TP molecules (each has 3C)
2 TPs will be removed to make Glucose
Leaves 10 TP molecules (30 Carbons)
10 x 3 Carbon TP = 30 Carbons = 6 x 5 Carbon RuBP molecules
83
Why does photorespiration reduce efficiency of photosynthesis
In high temperatures, stomata close to reduce transpiration
Prevents entry of CO2, CO2 conc falls and O2 levels increase
O2 competitively inhibits RuBisCo, leading to production of Phosphoglycolate, reducing production of GP
Phosphoglyolcate (2C) is a toxic molecule thy needs to be removed, or converted, which uses ATP
RuBisCo has higher affinity for CO2 than O2, and around 25% of products of Calvin cycle are lost in photorespiration
84
Explain why photorespiration is not something commercial producers would want to encourage
Less carbon dioxide fixed
less, organic molecules / named examples, synthesised
reduced yield
85
Suggest why plants evolved with such an important enzyme as a RuBisCO being inhibited by such a common molecule as oxygen
Photosynthesis produces oxygen
little / no, oxygen present in atmosphere when plants began to evolve
86
SUMMARY OF PHOTOSYNTHESIS DIAGRAM!!!!!!! PAGE 473
LOOK AT IT
87
Explain the meaning of the term photophosphorylation
Synthesis of ATP/addition of phosphate group to ADP
using energy from light
88
Explain why photosynthesis stops when plants are exposed to green light only
Green light is reflected/not absorbed
no energy for light-dependent stage
no ATP and reduced NADP for light-independent stage
89
Explain what is meant by the term fixation
Inorganic carbon
added to organic molecule
90
A) the Calvin cycle used to be called the dark reaction. This time is now rarely used. Explain why this time is incorrect.
B) explain why the alternative name of the Calvin cycle, the light, independent stage, is not completely accurate
A) Calvin cycle happens during the light as well
B) Calvin cycle requires ATP
and reduced NADP
supplied from light-dependent stage
91
Suggest the possible benefits of Cyclic photophosphorylation
ATP produced and reduced NADP not produced
electrons not required from PSII/photolysis
less ATP used in Calvin cycle
more ATP available for other metabolic processes
92
Describe how RuBP is regenerated from TP in the Calvin cycle.
10 molecules of TP every six turns of cycle
using ATP
6 molecules of RuBP formed
reference to (3/5) carbon shuffle
reference to individual steps/named light, enzymes, coenzymes, ATP
carbon dioxide does not combine directly with water
93
What are the 3 factors that affect the rate of photosynthesis and what impacts do they have
Light intensity - Needed as energy source, As light intensity increases, ATP and NADP are produced at a higher rate
Carbon Dioxide concentration - Needed as a source of carbon, increasing CO2 conc increases rate of fixation in Calvin Cycle, therefore rate of TP production,
Temperature - Affects the rate of enzyme-controlled reactions. As temperature increases, enzyme activity increases until the point at which they denature - increases carbon fixation, and photorespiration, due to high temps to reduce water loss, stomata will close
94
State two ways rate of photosynthesis can be measured
Data logger - with oxygen and light sensors which are computerised
Potometer/Gas syringe/ bubble technique - Measure release of gas in a certain time frame under many conditions
95
What effect does reducing the light intensity have upon the Calvin cycle
Reduces quantity of ATP and reduced NADP, which are needed to convert to convert GP to TP
Concentration of GP will increase as reduced conversion rates to TP
Less TP as less GP is converted
Less RuBP as less TP is present to regenerate it
Reverse will happen with increasing light intensity
96
How does Temperature affect the Calvin Cycle
Catalysed by enzymes
At lower temps, particles have less KE and DFOSC, meaning lower Concentrations of DP, TP and RuBP
At high temps, Enzymes will denature, same effect seen
97
How does the Carbon dioxide concentration affect the Calvin cycle
Low conc leads t predictions in DP and TP, RuBP will increase as it is not being used to fix carbon dioxide
Opposite for high conc
98
Suggest what you think would be the basic components of an artificial photosynthesis
Pigment/cell, to absorb light energy
catalyst to split water
enzyme to reduce carbon dioxide
any other sensible suggestion
99
When is C3 photosynthesis (normal) most efficient
Cool wet climates with average sunshine values
100
What are the 3 types of Photosynthesis
C3 photosynthesis
C4 photosynthesis
CAM photosynthesis (Crassulacean acid metabolism)
101
What are plants adapted for that use C4 photosynthesis
High temperatures and limited water supply
102
How does C4 photosynthesis differ from regular C3
Able to fix Carbon dioxide more efficiently, so their somata can close quicker so they lose less water by transpiration
PEP carboxylase in mesophyll cells, also fixes oxygen first, which increases frequency of fixation, then transported, decarboxylated then fixed to RuBisCo and enters Calvin Cycle
eg. corn
103
How does CAM photosynthesis work
Open stomata at night and close them during the day, reducing water loss by transpiration.
Carbon Dioxide converted to an acid and stored during the night
During the day, acid is broken down releasing CO2 to RuBisCo
During very dry spells, stomata can remain closed for day and night
Oxygen released by photosynthesis is used for respiration
eg. Cacti
104
Some plants drop their leaves and twigs and become dormant during dry spells. Describe the way in which a cactus survives dry spells and the advantages of this method
Cactus swells
storing water in wet periods
leaves are spines
small surface area
spines collect water (from atmosphere)
extensive and shallow root system
open stomata at night cactus / CAM plants, use PEP carboxylase to fix carbon dioxide
carbon dioxide stored until daytime
limited quantity stored limited photosynthesis so limited growth
105
Suggest why CAM plants can only keep their stomata closed night and day for short periods
Carbon dioxide required for photosynthesis
carbon dioxide enters plant through stomata
no, organic molecules / named examples, so no respiratory substrate
essential reactions / named examples, cannot take place
106
Describe what is meant by a limiting factor
Factor which limits rate of a process
e.g., light in photosynthesis
107
Suggest why the rate of oxygen production is only an estimate of the rate of photosynthesis
Oxygen is used in respiration
so not all oxygen produced is released
108
Discuss, using what you have learnt in this chapter, how an understanding of the effect of limiting factors on the rate of photosynthesis is used to design more efficient glasshouses
Limiting factors light, temperature, and carbon dioxide concentration
light is required for light- dependent stage
glasshouses are transparent / built from glass
carbon dioxide is required for light-independent stage
ventilation of glasshouse so concentration of carbon dioxide does not fall
temperature affects reactions in light-independent stage (and light-dependent stage)
use of heater
fossil fuel burners also release carbon dioxide
idea that each factor is maintained at a level that maximises the rate of photosynthesis but minimises waste
