Energy in cells
(Photosynthesis and Respiration)
Photosynthesis
• Chemical process that captures light energy and stores it as Chemical Potential Energy, only occurs in autotrophs
• Is a series of reactions controlled by enzymes• Occurs in the …• 2 Stages
– Light phase 1– Dark phase 2
Structure of a chloroplast
Granum – stacked thylakoids containing chlorophyll.
Stroma – clear liquid interior
How can you tell which phase occurs where?
How has surface area been maximised?
What is the green colour from?
Photosynthesis
The purpose is to capture light energy from the sun and store it as chemical energy in glucose molecules for use inside the plants. It also:•Removes carbon dioxide from the air •Needs water, gained by osmosis from the soil into the root hair cells and up the xylem vessels•Makes oxygen gas for use in respiration in all living organisms
Photosynthesis reaction summary:
Carbon dioxide + water glucose + oxygen + water
CO2 + H2O C6H12O6 + O2 + H20
Stages in PhotosynthesisStage Raw
materialsSource of raw materials
Products
(waste)
Location within
Chloroplast
Phase 1. Light or Light Dependent (LD)
Phase 2. Dark or Light Independent (LI)
Stages in PhotosynthesisStage Raw
materialsSource of raw materials
Products
(waste)
Location within
Chloroplast
Phase 1. Light or Light Dependent (LD)
Light
Water
ADP
NAPH
Sun
Air
Dark Reaction
ATP
NADPH2
(Oxygen)
Thylakoids of Grana
Phase 2. Dark or Light Independent (LI)
Carbon Dioxide
ATP
NADPH2
Air
Light Reaction
ADP
NAPH
Glucose
Stroma
Carrier molecules in Photosynthesis
• ATP – the energy carrier– ADP (empty)– Transports energy from light phase to dark
phase
• NADP – the hydrogen carrier– NADPH2 (full)– Transports hydrogen from light phase to dark
phase
See handout and discuss this concept in relation to the leaf model and the chloroplast diagram
How plants maximise the rate of photosynthesis
Factors affecting photosynthesis reaction rate:
Photosynthesis is controlled by enzymes so anything that affects enzymes also affects photosynthesis, including;•Light intensity (can differ for different plants, canopy verses forest floor plants), no photosynthesis in the dark!•Temperature (most plants have an optimum range)•CO2 concentration (substrate concentration)•Low water availability causes the stomata to close and CO2 diffusion to stop so photosynthesis stops as well.
Respiration
All living cells must carry out cellular respiration and the purpose is too release the energy stored in food (glucose) and make it available to power all other metabolic reactions (in both autotrophs and heterotrophs)
•Occurs in the (name organelle here?)
•There are two types (aerobic and anaerobic)
Structure of a mitochondriaCristae are the folded inner membranes. Why are they folded?
The matrix is the liquid inside . What stages take place here?
Mitochrondria are found in all living cells but in general animals cells have more than plants and any cells that need more energy have more e.g. muscle and liver cells have high energy demands so have more….
Aerobic Respiration (with O2)
• Cellular respiration with oxygen
• Also a series of reactions controlled by enzymes
• Glucose (food) and oxygen convert to lots of energy (ATP) with waste products of CO2 and H2O
C6H12O6 + 6O2 6CO2 + 6H2O + ATP glucose oxygen carbon dioxide water energy
4 stages of aerobic respiration
Stage Name Location in cell
Energy (ATP) produced
Link to equation
1
2
3
4
4 Stages of aerobic respiration (with oxygen)
– Glycolysis, – Link reaction , – Krebs cycle, – Electron transport chain
These stages are linked by carrier molecules in a similar way to photosynthesis reactions…
4 stages of aerobic respirationStage Name Location in
mitochondria or cell
Energy (ATP) produced
Link to equation
1 Glycolysis
(breakdown of glucose)
Cytoplasm 2 ATP Forms Pyruvate
No O2 needed
2 Link reaction Matrix none Forms Acetyl Co enzyme A and CO2
No O2 needed
3 Krebs Cycle or Citric Acid Cycle
Matrix 2 ATP Produces H2
No O2 needed
4 Electron Transfer Chain
Cristae 32 ATP O2 needed, combines with H2 to produce H2O
Carrier molecules in respiration (molecules that link stages of aerobic respiration)
• Co-enzyme A – an acetyl carrier– Acetyl co-enzyme A (full)– Transports acetyl group from glycolysis to
Krebs cycle
• NAD – the hydrogen carrier– NADH2 (full)– Transports hydrogen from Krebs cycle to
Electron transport chain
Anaerobic respiration (no O2)
• Respiration without oxygen• Another series of reactions controlled by
enzymes• Stops after glycolysis (stage 1)• Much less energy (ATP) produced• Different waste or by-products produced
• PlantsGlucose carbon dioxide + ethanol + 2ATP
• AnimalsGlucose lactic acid + 2ATP
Factors affecting respiration
All respiration reactions are controlled by enzymes …so again all things that effect enzymes affect both types of respiration, plus:
• Too much toxic product. Too much carbon dioxide (aerobic respiration) and too much ethanol or lactic acid (anaerobic respiration) is toxic. Toxic products must be removed during respiration for it to continue efficiently.
See Factors Affecting Enzymes…
•Temperature, •pH, •Surface Area, •Substrate (reactant) concentration,•Enzyme concentration, •Co-Factors (enzyme helpers), •Inhibitors (heavy metals, poisons).
ATP
• Adenosine triphosphate (ATP) is the universal energy carrier in all cells
• Cellular respiration is the process of recharging ADP (Adenosine diphosphate) to ATP
P
P
P
P
P
P
Role of ATP (Energy carrier molecule)
ATP ADP
Energy releasedfrom breaking off onephosphate (-P) from ATP.Where?
-P
+P
Respiration recharges ADP to ATP using energy and adding one phosphate (+P). Where?
Energy in cells summary
P/S
Respiration
Light Energy
CO2and
H2OGlucose
O2
O2
All Autotroph and Heterotroph cells
ATP
Heat Energy
H2O
CO2
Photosynthetic Autotroph cells
ADPkJ