Photosynthesis and Plant Anatomy Lecture Notes

Comprehensive practice questions covering the history of photosynthesis discovery, leaf anatomy, chemical reactions, and the endosymbiosis theory.

According to the initial hypothesis before the 17th century, where was it assumed plants got their matter from?

It was assumed that plants grew by “eating” soil.

In Jean Baptiste Van Helmont's five-year experiment with a Willow tree, what were the final mass results for the tree and the soil?

The tree increased to $76.8\,kg$ (from $2.3\,kg$), while the soil mass only decreased slightly to $90.76\,kg$ (from $90.8\,kg$).

What molecule did Joseph Priestley discover in his 1804 experiment using a mouse, a mint plant, and a bell jar?

Oxygen ($O_2$).

What are the primary components of air as mentioned in the lecture?

Nitrogen (Element), Oxygen (Element), Carbon dioxide (Compound), and Water (Compound).

What did Jan Ingenhousz demonstrate by observing underwater plants in sunlight and darkness?

He demonstrated that energy is needed for the process to occur, as plants only released Oxygen bubbles in the light.

How is energy classified in the context of sunlight vs. plant tissues?

Sunlight is kinetic energy because it travels in waves, while plant tissues are potential energy because they contain many chemical bonds.

What are the three wavelengths of electromagnetic radiation released by the sun that primarily affect life on Earth?

Ultraviolet (can damage living tissue), Visible (detectable by the human eye), and Infrared (heat energy).

Which specific wavelengths of visible light do plants use for photosynthesis, and which are reflected?

Plants use blue, orange, and red wavelengths; they reflect yellow and green wavelengths.

What was the conclusion of Nicolas de Saussure’s experiment with periwinkles?

Plants gain mass by absorbing Carbon dioxide from the air and converting it to sugars using sunlight.

What is the exact chemical equation for photosynthesis?

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$$

What is the function of the epidermis and the cuticle in a leaf?

The epidermis is a single cell layer that regulates gas exchange and protects inner tissues, while the waxy cuticle prevents the leaf from drying out.

How do guard cells maintain homeostasis in plants?

They surround the stomata and regulate gas exchange ($CO_2$ in, $O_2$ out) and water loss (transpiration) by changing turgor pressure.

What is the difference between xylem and phloem?

Xylem tubules transport and store water, while phloem tubules transport sugars and proteins.

Compare the functions of spongy mesophyll and palisade mesophyll.

Spongy mesophyll is porous tissue for gas exchange, while palisade mesophyll has the highest concentration of chloroplasts and is the primary site of photosynthesis.

What is the structure of a chloroplast?

It is a double-membraned organelle containing stacks of flattened disks called thylakoids and a fluid called stroma.

Where do the light-dependent reactions occur, and what happens when a photon strikes photosystem II?

They occur in the thylakoid membrane; the photon's energy excites electrons in water, causing it to split into oxygen and $H^+$ ions.

What is the role of ATP synthase in the light-dependent reactions?

It is a protein that $H^+$ ions flow through to generate ATP from ADP.

Distinguish between Chlorophyll a and Chlorophyll b based on their absorption.

Chlorophyll a (Photosystem I) absorbs blue-violet light best; Chlorophyll b (Photosystem II) absorbs red and blue light.

What is the Calvin Cycle, and where does it take place?

The Calvin Cycle is the light-independent reaction pathway that takes place in the stroma of chloroplasts.

Which enzyme is known as the “gateway to life” during the carbon fixation stage of the Calvin Cycle?

Rubisco, which helps attach Carbon dioxide to the 5-carbon molecule RuBP.

What occurs during the reduction phase of the Calvin Cycle?

ATP is dephosphorylated and NADPH is oxidized to produce G3P; two molecules of G3P can make one molecule of glucose.

What are amyloplasts?

Organelles in plant tissues where glucose molecules combined into starch are stored.

What is transpiration?

The process by which plants lose water through their stomata.

What is the Endosymbiosis Theory?

The theory that mitochondria and chloroplasts were once independent prokaryotic organisms that were engulfed by another cell.

What four unique structures do mitochondria and chloroplasts possess that support the Endosymbiosis Theory?

Inner and outer membranes, their own DNA, the ability to process energy, and they are self-replicating.