Organelles
• Membrane surrounds them• Important organelles:
• Nucleus• Cell membrane• Lysosomes/peroxisomes• Rough endoplasmic reticulum• Smooth endoplasmic reticulum• Golgi apparatus• Special organelles involved in energy:
• Mitochondrion—produces ATP (in all eukaryotes)• In plants and some algae: Chloroplast—produces sugar
from light energy
– A typical plant cell has some structures that an animal cell lacks
• Such as chloroplasts and a rigid cell wall
CentralvacuoleNot in
animalcells
Chloroplast
Cell wall
Golgiapparatus
Nucleus
Microtubule
CytoskeletonIntermediatefilament
Microfilament
Ribosomes
Smoothendoplasmicreticulum
Mitochondrion
Peroxisome
Plasma membrane
Roughendoplasmicreticulum
Figure 4.4B
Chloroplasts conver t solar energy to chemical energy– Chloroplasts, found in plants and some protists – conver t solar energy to chemical energy in sugars
TEM
9,7
50
Chloroplast
Stroma
Intermembranespace
Inner and outermembranes
Granum
Figure 4.14
Chloroplast Structure
Chloroplast
Photosynthesis
• Chlorophylls have Mg at center
Perceived Color
Let There Be Light
The ‘Z’ scheme of photosynthesis
ATP
Synthase
Figure 7.5
Light
CO2H2OChloroplast
LIGHTREACTIONS
(in thylakoids)
CALVINCYCLE
(in stroma)
NADP+
ADP+ P
ATP
NADPH
O Sugar
Electrons
2. Carboxylation
3. Reduction
1. Preparation
CO2 + H2O
3-Phosphoglycerate
ATP
+
NADPHADP
Pi+
Glyceraldehyde-3-phosphate
(PGAL)
Triose phosphates
Sucrose, starch
ATP
ADP
Pi
Ribulose-1,5-bisphosphate
+
Left: a starch grain that has formed inside the chloroplast.
Metabolism: Sugars & Starches• Starch forms in
chloroplast• Sucrose forms in
cytoplasm outside chloroplast
• In the chloroplast, sugars & starches compete for the same metabolic pathways in order to be made
• Enzyme involved is fructose-2,6-bisphosphate
• If cell is in light, it makes sugar; if in dark, makes starches
C3 Photosynthesis: problems
• The enzyme rubisco (ribulose bisphosphate carboxylase):– 1. Stops working at or above 90F– 2. Equal affinity for oxygen & carbon
photorespiration• Light: only uses ~30% of available light
energy• --no way to concentrate CO2
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