photosynthesis- chapter 11

Question 1

where is the site of photosynthesis

Answer 1

-The leaf is a main photosynthetic structure in eukaryotic plants.
-Chloroplasts are the cellular organelles within the leaf where photosynthesis takes place.

Question 2

what are the adaptations of the structure of the leaf

Answer 2

1. A large surface area that absorbs sunlight.
2. An arrangement of leaves on the plant that minimises overlapping
3. Thin to keep diffusion distance short and absorb as much light as possible.
4. A transparent cuticle and epidermic that let light through to the photosynthetic mesophyll cells beneath.
5. Long, narrow upper mesophyll cells packed with chloroplasts that collect sunlight.
6. Numerous stomata for gaseous exchange so that all mesophyll cells are only a short diffusion pathway from one.
7. Stomata that open and close in response to change in light intensity
8. Many air spaces in the lower mesophyll layer to allow rapid diffusion in the gas phase of carbon dioxide and oxygen
9. A network of xylem that brings water to the leaf cells, and phloem that carries away the sugars produced during photosynthesis

Question 3

what are the three main stages of photosynthesis and describe them shortly

Answer 3

1. Capturing of light energy- by chloroplasts pigments such as chlorophyll
2. The light-dependent reaction, in which some of the light energy absorbed is conserved in chemical bonds. An electron flow is created by the effect of light on chlorophyll, causing water to split (photolysis) into protons, electrons and oxygen. The products are reduced NADP, ATP and oxygen.
3. The light-independent reaction, in which these protons are used to produce sugars and other organic molecules.

Question 4

what is the equation for photosynthesis

Answer 4

Carbon dioxide + Water 🡪 Glucose + Oxygen
6CO2 + 6H2O 🡪 C6H12O6 + 6O2

Question 5

what is the structure of chloroplasts

Answer 5

-Chloroplasts vary in shape and size but are typically disc-shaped, 2-10um long, and 1um in diameter.
-Surrounded by a double membrane

Question 6

what are the two distinct regions inside the chloroplasts

Answer 6

grana and stroma

Question 7

describe the grana

Answer 7

-They are stacks of up to 100 disc-like structures called thylakoids where the light-dependent stage of photosynthesis takes place.
-Within these is the pigment chlorophyll.
-Some thylakoids have tubular extension that join up with thylakoids in adjacent grana, these are called intergranal lamellae

Question 8

describe the stroma

Answer 8

-The fluid-filled matric where the light-independent stage of photosynthesis takes place.
-Within the stromata are a number of other structures such as starch grains