photosynthesis & respiration. ecology is the study of the relationships between organisms and...

Photosynthesis & Respiration

ENERGY TRANSFORMATIONS IN NATURE

• Ecology is the study of the relationships between organisms and their environment and an Ecosystem is a community of organisms in a habitat and how they interact with each other and the environment that they live in.

• One of the key parts to ecology is the study of how energy moves through an ecosystem.

• Where does this energy come from?• Why is it so important?• How does it flow through an ecosystem?• What factors can effect its movement?

• By developing an understanding of the answers to these questions, scientists can get a good sense of what drives an ecosystem and what is required to make that ecosystem sustainable

ENERGY in NATUREINTRODUCTION

ENERGY in NATURE

• All ecosystems depend on energy input for them to be able to work

• The energy is important because organisms use it for:

- movement - keeping warm - growth and repair - metabolic function - chemical synthesis

• Without this energy, organisms are unable to function/move/reproduce and the biotic components of ecosystem may die very quickly

THE NEED FOR ENERGY

ENERGY in NATURE• The original source of energy in an

ecosystem comes from the SUN

• Plants, algae and cyanobacteria are all able to trap the sun’s energy and use it to create energy rich organic material in a process called PHOTOSYNTHESIS

• These organisms are called AUTOTROPHS or PRODUCERS as they supply all of the organic matter and energy on which the other organisms in an ecosystem depend

THE SOURCE OF ENERGY

TYPES of AUTOTROPHS• Photosynthesis evolved as a way to

store the energy in solar radiation as high-energy electrons in carbohydrate molecules (solar energy chemical energy)

• Plants, algae and cyanobacteria, known as photoautotrophs, are the only organisms capable of performing photosynthesis

• Energy is acquired by living things in three ways: photosynthesis, chemosynthesis and consumption

• Photosynthetic and chemosynthetic organisms are grouped into a category known as autotrophs: organisms capable of synthesising their own food (more specifically, capable of using inorganic carbon as a carbon source)

• Autotrophs act as producers and are critical for ALL ecosystems. Without these organisms, energy would not be available to other living organisms and life itself would not be possible

TYPES of AUTOTROPHS

• A Photoautotroph is an organism that can synthesise its own food by using light as a source of energy

• Photoautotrophs, such as plants, algae, and photosynthetic bacteria, serve as the energy source for a majority of the world's ecosystems. These ecosystems are often described by grazing food webs

• Photoautotrophs harness the solar energy of the sun by converting it to Chemical energy in the form of ATP (and NADP). The energy stored in ATP is used to synthesise complex organic molecules, such as glucose

Photoautotrophs

Euglenia

TYPES of AUTOTROPHS

• VIDEO: David Attenborough on Geothermal Vents • A chemoautotroph is a simple organism, such as

bacteria or protozoans, that derives its energy from chemical processes rather than photosynthesis

• Chemoautotrophs are primarily bacteria that are found in rare ecosystems where sunlight is not available, such as in those associated with dark caves or hydrothermal vents at the bottom of the ocean . Many chemoautotrophs in hydrothermal vents use hydrogen sulfide (H2S), which is released from the vents, as a source of chemical energy. This allows chemoautotrophs to synthesise complex organic molecules, such as glucose, for their own energy and in turn supplies energy to the rest of the ecosystem.

• Chemoautotrophs make their food using chemical energy rather than solar energy.

• Chemoautotrophs are able to synthesise their own organic molecules from the fixation of carbon dioxide.

• Chemoautotrophs are able to thrive in very harsh environments, such as deep sea vents, due to their lack of dependence on outside sources of carbon other than carbon dioxide.

Hydrothermal vents

Chemoautotrophs

Swimming shrimp, a few squat lobsters and hundreds of vent mussels are seen at a hydrothermal vent at the bottom of the ocean. As no sunlight penetrates to this depth, the ecosystem is supported by chemoautotrophic bacteria and organic material that sinks from the ocean’s surfaceVIDEO: David Attenborough on Geothermal Ventshttps://www.youtube.com/watch?v=BXGF3XS-yAI

https://www.youtube.com/watch?v=BXGF3XS-yAl

https://www.youtube.com/watch?v=BXGF3XS-yAl

https://www.youtube.com/watch?v=BXGF3XS-yAI



Photosynthesis vs Chemosynthesis

PHOTOSYNTHESIS

PHOTOSYNTHESIS• Photosynthesis is the conversion of light energy

from the sun into chemical energy that can be utilised by living organisms as an energy substrate in cellular respiration

• The process occurs in organelles called CHLOROPLASTS. The grana of the chloroplasts (looks like a stack of 20 cent coins) contains the chemical CHLOROPHYLL.

• Chlorophyll is able to absorb the suns energy and

use it to excite molecules to a higher energy level. This sets off a series of chemical reactions that ultimately result in the formation of an organic molecule namely GLUCOSE

• Photosynthesis occurs in 2 stages: Light dependent phase (in the grana) Light independent phase (in the stroma)


PHOTOSYNTHESIS

PHOTOSYNTHESIS• Photosynthesis can be summarised by the following word and chemical

equations:Carbon Dioxide + Water Glucose + Oxygen

6CO2 (g) + 6H2O (l) C6H12O6 (s) + O2 (g)

• The Inputs are CO2 and H2O. Carbon dioxide comes from the atmosphere and enters plants through the stomata. Water enters the plants via the roots in the ground and travels to the leaves via the xylem

• The Outputs are Glucose and Oxygen. The glucose is then used in Cellular respiration and the Oxygen is released as a waste (although some can be used in Cellular Respiration)

• The rate of photosynthesis depends the concentrations of Carbon dioxide and Water as well as factors such as temperature and light intensity

VIDEO: Crashcourse Photosynthesishttps://www.youtube.com/watch?v=sQK3Yr4Sc_k


https://www.youtube.com/watch?v=sQK3Yr4Sc_k

https://www.youtube.com/watch?v=sQK3Yr4Sc_k

STAGES of PHOTOSYNTHESISLight Dependent Reaction• Sunlight excites the chlorophyll

molecule in PHOTOSYSTEM II• The energy produced helps break

down a water molecule (PHOTOLYSIS)

• H+ are released into the thylakoid space

• O2 is a by-product released• The removed electrons (e-) are

excited to a higher energy state and then excited again (by Photosystem I) to an even higher energy state

• These electrons are then used to convert the NADP into NADPH (a carrier molecule)

• Transports H+ across the thylakoid membrane

• This causes a CHEMIOSMOTIC gradient for H+ to diffuse back through the membrane which activates ATP SYNTHASE

• This combines ADP with inorganic phosphate to produce ATP

• The highly energetic NADPH and ATP molecules are then fed into the light-independant reaction

STAGES of PHOTOSYNTHESIS Light Independent Photosynthesis (THE CALVIN CYCLE)

• The second stage of photosynthesis takes place in the STROMA

• It can occur WITHOUT the presence of sunlight

• It is known as the CALVIN CYCLE - ATP & NADPH (the products of light dependant phase are used to convert

CO2 to GLUCOSE)

RuBP (Ribulose Biphosphate) is a 5-carbon sugar that binds C02 dissolved in the stroma

This unstable molecule quickly breaks down to two molecules of 3-carbon 3-phosphoglycerate (3PG)

The 2 3PG molecules are then converted into glyceraldehyde 3-phosphate (G3P)

(by adding a high energy phospahte group

from ATP and adding Hydrogen from NADPH)

2 molecules of G3P (multi turns of the Calvin cycle) combine to form 1 molecule of glucose

G3P is also the starting point for the synthesis of fats and proteins

RATE OF PHOTOSYNTHESIS

LIGHT-Brighter the light the faster the rate of photosynthesis-Photosynthesis greater on bright sunny day and out of the shade-Up until a point where another factor limits the rate of photosynthesis-Plants are adapted to certain conditions so if exposed to full light they will die eg. FernsCO2

-Raw material of photosynthesis-Changes in its concentration effect the rate of photosynthesis-More CO2, stomata open, greater the rate of photosynthesisWATER-Raw material of photosynthesis-Lack of water slows photosynthesis-May cause stomata to close thus reducing CO2 uptake-Other processes also affected by the lack of waterTEMPERATURE-Generally increases as the temperature increases-Only to a certain temperature as the enzymes denature at around 40oC-Certain plants are adapted to live in certain temperatures LIMITING FACTORS THE FACTOR WHICH IS LEAST AVAILABLE DETERMINES THE RATE AT WHICH PHOTOSYNTHESIS OCCURS. THE FACTOR IS THE LIMITING FACTOR.

LEAF ADAPTATIONS FOR PHOTOSYNTHESIS1. Waterproof Cuticle - prevents water escaping or being evaporated - water is crucial as a raw material for photosynthesis: transport medium and other functions2. Chlorophyll (palisade mesophyll) - palisade mesophyll are packed with green chloroplasts - packed on the upper side of the leaf which receives most sunlight3. Air Spaces - large air spaces exist between the spongy mesophyll - allows air to circulate freely through the interior of the leaf - CO2 is able to diffuse into these spaces - Contain water vapour which keeps cell surface moist and

allows CO2 to diffuse through membranes - O2 also can diffuse into these spaces (out during day/in during night)4. Transport Tissues - network of veins provide strength to the leaf and carry water

and minerals from roots to leaves - sugars carried from leaves to other parts of the plant5. Stomata - mostly on the lower (shaded) sides of leaves - cooler and less exposure to sunlight so minimal water

evaporation - allow CO2 and O2 diffusion in and out

C3, C4 and CAM PlantsC3 Plants-Plant species that fix carbon exclusively through the Calvin cycle-The most common pathway for carbon fixation-On hot days stomata close so C3 plants can conserve water, but CO2 then cannot diffuse inC4 Plants-CO2 is stored in mesophyll cells. It is joined to a 3-carbon molecule to form a 4-carbon molecule (hence name C4 plants)-It then fixed by Rubisco (enzyme that helps bind CO2 to RuBP) in the Calvin cycle-CO2 gradient remains low in mesophyll cells allowing it to naturally diffuse in, even when stomata are almost closed-Means that photosynthesis can occur more readily in hot conditions when the stomata would otherwise be closed

Eg. Corn, Sugar CaneCAM Plants (Crussulacean Acid Metabolism)-CO2 gathered at night and forms malate (4 Carbon)-CAM plants dont transport it away from mesophyll but store it during the night-Use these for the Calvin Cycle during the day-Requires 4 more ATP molecules than C3 so tend to grow more slowly-Lose up to 95% less water than C3 plants as stomata are only open at night-useful in arid zones-Can swap to C3 for brief periods when water is available or to keep stomata closed day & night during drought

VIDEO: Plant Adaptations for Photosynthesishttps://www.youtube.com/watch?v=DGpPHrLF-5M

https://www.youtube.com/watch?v=DGpPHrLF-5M



A.T.P – ADENOSINE TRIPHOSPHATE• ATP ADP + Pi ATP can be broken down into ADP and inorganic phosphate to release energy to drive other chemical reactions

• ADP + Pi ATP ADP and inorganic phosphate can be joined to create ATP. This stores energy and allows it to be transported around the cell

• To make 1 ATP requires 30.7KJ to be stored in the last bond• Any reactions that produce less than 30.7KJ can’t store the energy which is then lost as HEAT• Any reactions that produce more than 30.7KJ have the excess released as HEAT• HELPS KEEP US WARM + WHY ENERGY IS LOST OUT OF FOOD WEBS

• Catabolic ReactionHydrolysis

• Anabolic ReactionRephosphorylatio

n

HETEROTROPHS• Heterotrophs are organisms that are

unable to produce their own food, they function as consumers in the food chain.

• They rely on the carbohydrates produced by photosynthetic organisms for their energy needs

• They obtain energy in the form of organic carbon by eating autotrophs or other heterotrophs.

• They break down complex organic compounds produced by autotrophs into simpler compounds, releasing energy by oxidising carbon and hydrogen atoms into carbon dioxide and water, respectively.

• Unlike autotrophs, heterotrophs are unable to synthesise their own food. If they cannot eat other organisms, they will die.

• #NOTE: Both autotrophs and heterotrophs undertake cellular respiration. It is how they obtain the substrate (eg. Glucose) that differs

CELLULAR RESPIRATION

CELLULAR RESPIRATION

• The products are vitally important to all organisms.

• In particular the carbohydrate (glucose) produced is used as the substrate for the process of cellular respiration. This is the process all organisms use to make usable energy in the form of ATP.

• The Oxygen produced in photosynthesis is also a vital ingredient in cellular respiration

• During the process of cellular respiration not all energy is converted into ATP and some is lost as heat energy.

• This loss of energy as heat helps maintain the internal temperature of organisms but it also has a significant effect on how food chains and webs can function as we will see later

• Overall CELLULAR RESPIRATION can be summarised as:

Glucose + Oxygen Carbon Dioxide + Water

C6H12O6 (s) + O2 (g) 6CO2 (g) + 6H2O (l)

WHY IS PHOTOSYNTHESIS SO IMPORTANT

VIDEO: Photosynthesis & Cellular Respiration

https://www.youtube.com/watch?v=3XIyweZg6Sw



STAGES of CELLULAR RESPIRATIONGlycolysis and Krebs Cycle

GLYCOLYSIS KREB’S CYCLE

STAGES of CELLULAR RESPIRATIONOxidative Phosphorylation (The Electron Transport Chain)• Then Oxygen is used as the FINAL

ELECTRON ACCEPTOR• - the H+ ions combine with the • oxygen to form water

• 2H+ + ½ O2 + 2e- H2O

• Oxygen is crucial and the electron transport chain cant work without it

• - it helps create a concentration • gradient by taking away H+

• 1 NADH (from Glycolysis) = 3 ATP• 3 NADH (from Krebs) = 9 ATP• 1 FADH (from Krebs) = 2 ATP• 1 NADH (from Transition) = 3 ATP

• Total = 17 ATP per Pyruvate therefore • 34 ATP PER GLUCOSE

CELLULAR RESPIRATION – Where it all occurs

ANAEROBIC RESPIRATION• Cellular Respiration generally requires oxygen (for the removal of CO2 and as the last H+

acceptor during the electron transport chain)

• Aerobic Respiration generates A LOT OF ENERGY (36 ATP)

• Anaerobic Respiration is the partial breakdown of glucose to obtain energy WITHOUT OXYGEN

• It occurs in the cytoplasm of the cell

• The products of anaerobic respiration (ethanol & lactic acid) are toxic

• The reactions cant carry on indefinitely and do not produce a large amount of energy

VIDEO: BOZEMAN ANAEROBIC RESPIRATION SUMMARY

https://www.youtube.com/watch?v=cDC29iBxb3w



Anaerobic Respiration

The Ethanol Pathway In Yeast

The Lactate Pathway In Mammals

Alcoholic fermentation: SUGAR ETHANOL + CO2 + ENERGY

• Anaerobic respiration in muscle cells that produces lactic acid• Lactic Acid causes burning and tiring of muscles during strenuous exercise• Lactic Acid is transported to the liver via the blood converted into pyruvate requiring oxygen the O2 required is called OXYGEN DEBT

ANAEROBIC RESPIRATION

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Photosynthesis

Photosynthesis is the process where:

A) heterotrophs obtain food by eating plants.

B) autotrophs use sunlight to make organic molecules.

C) heterotrophs synthesize glucose from sunlight and CO2.

D) autotrophs depend on detritivores for their food source.

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Photosynthesis

Photosynthesis is the process where:

A) heterotrophs obtain food by eating plants.

B) autotrophs use sunlight to make organic molecules.

C) heterotrophs synthesize glucose from sunlight and CO2.

D) autotrophs depend on detritivores for their food source.

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Photosynthesis

Which structure specifically absorbs light in a plant cell?

A) mitochondrion

B) thylakoid membrane

C) stroma

D) guard cell


Photosynthesis

Light-independent reactions use energy harvested from light-dependent reactions to:

A) produce both NADPH and ATP.

B) drive the assembly of sugar molecules from carbon dioxide.

C) activate light reactions through enzymes.

D) convert chemical energy in one of two photosystems.


Cellular Respiration

Which of the following statements about cellular respiration is true?

A) Chemical energy, in the form of glucose and oxygen, is the primary source of energy.

B) Plants use solar energy to turn glucose into oxygen.

C) All organisms can use sunlight to produce chemical energy, stored as glucose and oxygen.

D) Cellular respiration occurs only in plants and cannot be performed by mammals.



Which of the following statements about cellular respiration is true?

A) Chemical energy, in the form of glucose and oxygen, is the primary source of energy.

B) Plants use solar energy to turn glucose into oxygen.

C) All organisms can use sunlight to produce chemical energy, stored as glucose and oxygen.

D) Cellular respiration occurs only in plants and cannot be performed by mammals.






What is the main difference between aerobic and anaerobic respiration?

A) Whether or not oxygen is used as final electron acceptors.

B) The stage where fermentation takes place.

C) The stage at which lactate dehydrogenase in used in the respiration process.

D) Whether the final electrons are positively or negatively charged.



Organisms that can make their own food using inorganic molecules are called__________, while organisms that make their own food using light energy are called___________.

A) heterotrophs; chemoautotrophs.

B) chemoautotrophs; photoautotrophs.

C) heterotrophs; photoautotrophs

D) photoautotrophs; chemoautotrophs



What is the net outcome of glycolysis from one molecule of glucose?

A) Two ATP, two NADH, and two pyruvate molecules

B) One ATP, one NADH, and one pyruvate molecule

C) Four ATP

D) One ATP and two NADH molecules

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