AP® Biology—Semester A

Sample Lesson - Introduction

Lesson 2.03: Eukaryotes

"Dude. Get out of my cesspool."
(Source)

Back in the good old days, being a prokaryote was fun. A bacterium could relax and let its hair down. They didn't have to share the cesspool, the archaeal cell next door was always excreting the tastiest treats, and the local softball team, the Chemotrophs, were off to a great start. Then one day, some bacterium got a little too big for his breeches and decided to eat that archaeal cell next door. And just like that, blamo! A eukaryote was born.

Scientists believe that eukaryotes likely evolved when one prokaryote ate another and the one that got eaten just kept doing its thing from inside the other cell. After several billion years of evolution, we now have protists, fungi, algae, plants, and animals all wiggling around on planet Earth.

Even though we are pretty different from plants and fungi (well, at least we like to think so), our cells have a lot of similarities thanks to that common eukaryotic ancestor. In this lesson, we'll go over the structure and function of organelles found in eukaryotic cells. We'll also do some comparing and contrasting between the prokaryote and eukaryote camps.

Sample Lesson - Reading

Reading 2.2.03: The Inside Stuff

Let's look inside you. Say "Ahhhh." If you have a microscope handy, we can take a swab of your cheek cells and look at them up close and personal. Or you can read about the inner workings of your eukaryotic cells without lifting a finger, or donating part of your cheek, by checking out this reading.

Pay attention to all of the terms in the reading. There are a lot of cellular components to get familiar with, and in future units, we'll be referring back to these organelles. Take some notes on their form and function, and perhaps even make a few sketches in your notes. Colored pencils and 3D rendering optional.

Now that introductions are over, let's deep dive into the different organelles eukaryotic cells can have. They're what set the eukaryotes apart from the prokaryotes, after all. This reading has all the deets.

These cellular mini organs aren't stand-alone units. They interact with each other like dancers in a ballet (or if ballet isn't your thing, like the way trainers interact with their Pokémon). Each organelle has a specific job to do, and once they've completed that job, they send their products to the next organelle to be processed, packaged, or shipped, much like the way the post office handles packages. Luckily for us, our organelles are a lot more efficient than human-involved mail handling.

Cells with Walls

Whew. Cells have lots of organelles, but the fun doesn't stop there. There are a few organelles that are unique to plant and fungi cells. Animals are all jealous, so best not to mention their lack of chloroplasts or cell walls if you don't want a passive aggressive episode on your hands.

They'll get over it, because there are a few cell structures of which animals can be proud. Read about the animal-only organelles here.

Summary

• Eukaryotes are cells with organelles, like nuclei and mitochondria. They're more complex than their prokaryote cousins are.
• Eukaryotes and prokaryotes share a few common features, like cytoplasm and cytoskeletons. Just like in prokaryotes, the cytoskeleton helps give the cell its shapely figure and move components around the cell.
• Eukaryotic cells are full of organelles, so know which ones go where and what they do. Here's a very brief description (in alphabetical order), but go back to the linked readings or the Terms list for more info.
  • Cell wall: In plants and fungi (and prokaryotes), the cell wall provides added structural stability for the cell and serves as a permeability barrier.
  • Centrioles: Barrel-shaped protein tubes found in animal cells that aid in cell division.
  • Chloroplasts: The photosynthetic organelles found in plants. These guys absorb energy from the sun and use it to start a chain reaction that leads to sugar formation.
  • Cytoplasm: The liquid insides of the cell (called cytosol) plus all the organelles.
  • Endoplasmic reticulum: Comes in rough and smooth varieties. Rough ER makes proteins and smooth ER makes lipids.
  • Golgi body: The shipping department at Cell & Co. The Golgi receives lipids and proteins from the endoplasmic reticulum and processes them and packages them into vesicles for transport or secretion.
  • Lysosomes: These are the garbage men of the cell. They gobble up cellular debris and waste products through phagocytosis and then digest them.
  • Mitochondria: The energy factories of the cells. These little guys are the site of cellular respiration and turn sugar into ATP energy.
  • Nucleus: The brain of the cell. This is where the DNA lives and where it gets transcribed into RNA to direct protein synthesis.
  • Plasmodesmata: Spaces in the cell wall of plants that allows intercellular communication to occur.
  • Ribosomes: The site of protein synthesis in the cell. These are found in all forms of life. The rough ER is bound with lots of ribosomes to facilitate polypeptide production.
  • Vacuole: In plants, the vacuole is the largest structure in the cell and is a water tank that fills with water to maintain turgor pressure. Animals and fungi have vacuoles too, but they're much smaller and are storage compartments for all sorts of chemical necessities.
  • Vesicles: Little membrane bubbles that bud off the Golgi body. These are like shipping containers that take proteins and lipids to their final destination.

Sample Lesson - Activity

Activity 2.03a: Organelle Report Cards

Remember elementary school? Those were the days. We brought home report cards with stickers and good grades for sitting crisscross applesauce (spoon in the middle, optional). Today we're going to draw on the good ole days and send some organelles back to kindergarten.

Today, let's imagine that we're kindergarten teachers for a subcellular classroom full of organelles. Soon it will be report card time, and it is your responsibility to tell the proud parents how their little organelles are doing within your cell. Everyone knows that kindergarten is where you learn to play well with others. Do these organelles play well with others? With whom do they interact? What are their favorite activities? Can they color inside the lines?

Pick two organelles, one common to all eukaryotes and one that's unique to only one type of cell (animal, plant, or fungi), and write up report cards for each of them. Go back to the information from this lesson's Reading to help you. If you need to fill in any gaps, the British Society for Cell Biology has some useful information on cells and their organelles (scroll about halfway down the page and there are links for each organelle).

At a minimum, your report card needs to answer the following questions:

• What is the organelle's name?
• How does the organelle spend its time in class (i.e. in the cell)?
• How does the organelle interact with others in the class?
• What is the quality of work the organelle produces and how/where are those products used in the cell?
• How does the organelle contribute to the cell's overall function?
• What would happen to the cell if the organelle is absent or refuses to participate?

You should format your report card like an actual report card. There are tons of templates on the interwebs that you can use that will provide inspiration. It's also totally fine to give your student bad grades if you're drunk with power from being teacher for a day. Just make sure you explain why the organelle isn't cutting it and ways it could improve.

When you're done, you should have two report cards ready to send home to some anxious organelle parents. Since organelles don't have parents, though, just upload them to your teacher using the button below.

Sample Lesson - Activity