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