Journey To The Center Of Leaf

​ ​ It might seem unintuitive, but a plant's leaf is a(n)​ ​ (a)   , just like a heart, a bone, or a lung.

The whole redwood we are observing is a(n) ​ (b)   .

Together, all the redwoods in the forest are the ​ (c)   , and the redwoods with the other types of tree, the squirrels, and the ant climbing along this leaf is a(n) ​ (d)   . If you include the air and water, that's the ​ (e)   .

Unfamiliar with any of the words in the drop-down? Learn them using the link for "Biological Organization" on Canvas.

• organ
• tissue
• organism
• organelle
• community
• population
• ecosystem
• cell
• molecule

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This structure, the pore in the leaf we are passing is called the:

I used this word when we talked it through. If you need to make this mistake, make this mistake; you'll get the feedback with the right answer next, and the next question has a diagram with this word that you can label and learn from.

• stoma

• stroma

• cytosol

• chloroplast

• matrix

Answer explanation

Stoma; not to be confused with stroma, another word we will learn soon.

For the love of all things hole(y), please don't google stoma without adding 'plant'. They are a result of a surgical procedure in humans and it's a bit grisly if you're not expecting it.

A stoma is a pore in a leaf. Just like your pores in your face, the stoma can be closed or ​ ​ (a)   , to allow substances to pass through.

Control of the stoma is performed by the ​ (b)   . This organelle can be more or less full of water; when it is full, it swells and causes the shape of the cells around the stoma to close the gap.

• open
• vacuole
• vesicle
• cytoplasm
• membrane
• chloroplast
• shut

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We are looking at a plant cell. Here is quick review of some major organelles.

​ (a)   prevents this plant cell from blowing up when given too much water, or shrinking and collapsing; it's structural protection that is made of cellulose.

​ (b)   manages transport. Reactants must be imported, products are often exported.

​ ​ (c)   supports and nourishes the organelles. The gaseous reactants and products that pass into the cell must diffuse and permeate through this substance.

​ (d)   generates energy from the oxidation of simple sugars; that was last week's work.

​ (e)   converts solar energy into chemical energy; it's the focus of this lesson.

​

• Membrane
• Chloroplast
• Cytosol
• Mitochondria
• Ribosome
• Nucleus
• Endoplasmic Reticulum
• Wall

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We are swimming through the...

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We have just passed into the chloroplast.

DESCRIBE the theory of the origin of the chloroplast, and PROVIDE at least TWO pieces of evidence for this theory.

Struggling? Can you draw it instead?

Please don't research. There will be feedback after in the form of a GUIDED question, instead of free-response and it's better that you know you don't know.

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Support for DESCRIBE the theory of the origin of the chloroplast:

The theory of ​ (a)   describes how ​ (b)   , with their complex organelles, evolved from ​a precursor cell that engulfed (c)   .

​ (d)   are descended from aerobic bacteria and chloroplasts are descended from ​ (e)   .

• endocytosis
• evolution
• endoplasmic reticulum
• plant cells
• animal cells
• endosymbiosis
• eukaryotes
• prokaryotes
• Mitochondria
• cyanobacteria

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Select true discovered evidence for the theory of endosymbiosis.

• Chloroplasts and mitochondria have DNA that reflects a prokaryotic ancestor capable of the same processes they are capable of.

• Chloroplasts and mitochondria independently reproduce in the manner of bacteria.

• Chloroplasts and mitochondria have double membranes; the external from the proto-eukaryote, the internal from the prokaryote.

• Chloroplasts and mitochondria each have cell walls, like prokaryotes.

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This substance that we are passing through is the stRoma, the 'cytosol' of the chloroplast. It is not to be confused with the matrix, which is the 'cytosol' of the mitochondria.

StRoma should also not be confused with the ???, which is a pore in the surface of the leaf that we passed through at the start of this video.