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 Central vacuole Not in animal cells Chloroplast Cell wall Golgi apparatus Nucleus Microtubule Cytoskeleton Intermediate filament Microfilament Ribosomes Smooth endoplasmic reticulum Mitochondrion Peroxisome Plasma membrane Rough endoplasmic reticulum 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 9,750  Chloroplast Stroma Intermembrane space Inner and outer membranes 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 CO 2 H2OH2O Chloroplast LIGHT REACTIONS (in thylakoids) CALVIN CYCLE (in stroma) NADP + ADP +P ATP NADPH OSugar Electrons

2. Carboxylation 3. Reduction 1. Preparation CO 2 + H 2 O 3-Phosphoglycerate ATP + NADPH ADP 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