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
+
H2 O
C6H12O6 + O2 + H20
Stages in Photosynthesis
Stage
Phase 1.
Light or
Light
Dependent
(LD)
Phase 2.
Dark or Light
Independent
(LI)
Raw
Source
Products Location
materials of raw
within
(waste)
materials
Chloroplast
Stages in Photosynthesis
Stage
Phase 1.
Light or
Light
Dependent
(LD)
Phase 2.
Dark or Light
Independent
(LI)
Raw
Source
Products Location
materials of raw
within
(waste)
materials
Chloroplast
Light
Sun
ATP
Thylakoids
Water
Air
NADPH2 of Grana
ADP
Dark
(Oxygen)
Reaction
NAPH
Carbon Air
ADP
Dioxide
NAPH
ATP
Light
Glucose
NADPH2 Reaction
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
How plants maximise the rate of photosynthesis
See handout and discuss
this concept in relation to
the leaf model and the
chloroplast diagram
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 mitochondria
Cristae 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
1
2
3
4
Name
Location in
cell
Energy (ATP)
produced
Link to equation
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 respiration
Stage
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
• Plants
Glucose  carbon dioxide + ethanol + 2ATP
• Animals
Glucose  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
Role of ATP
(Energy carrier molecule)
-P
ATP
Energy released
from breaking off one
phosphate (-P) from ATP.
Where?
ADP
+P
Respiration
recharges ADP to ATP
using energy and
adding one phosphate
(+P). Where?
Energy in cells summary
Photosynthetic Autotroph
cells
Light Energy
All Autotroph and
Heterotroph cells
O2
CO2
and
P/S
H2O
Glucose
kJ
ADP
Respiration
ATP
H2O
Heat Energy
CO2
O2