Fall2025-week02-Proteins, Cells, and Organelles Unpacked

Eric Marquette

Welcome back to Bio 259 Recap, everyone! I'm Eric—here as always with the ever-thoughtful Avery Lin. Hope you're ready to nerd out about proteins, cells, and organelles, because we've got some epic biology coming your way. Avery, how are you doing over there?

Avery Lin

Hey Eric! I’m jazzed as usual. Did you know if you take out all the water, bones, and fat, about 75% of what’s left in your body is just… protein? That blew my mind in lecture.

Eric Marquette

Yeah, it’s wild! Most folks just associate protein with muscle, but it's way more fundamental. Proteins are everywhere—your hair, skin, ligaments. Kind of like the duct tape and super glue of the human body rolled into one.

Avery Lin

But Eric, let me flip it: Is it possible to get too much of a good thing? Like, what actually happens if someone overdoes the protein shakes? I’m betting our listeners are just as curious.

Eric Marquette

Yeah, there are some legit risks! Excess dietary protein can put your kidneys into overdrive, leading to strain over time—especially because breaking down all those amino acids creates nitrogenous waste that the kidneys have to filter. Overdo it for long enough, and you could be looking at real kidney issues, or worse. Some studies also link super high protein diets—especially from lots of red meat—to higher risks of heart disease. Oh, and extra calories from protein? They get stored as fat, just like anything else. It's all about balance.

Avery Lin

Exactly! So next time you’re considering a third scoop of powder, remember: your body’s got limits. And speaking of the body... let’s get into how these proteins actually work on the tiniest scale. Because the way proteins fold and organize is, honestly, just as fascinating as what they do, right?

Eric Marquette

Totally. So, quick run-through: proteins have four levels of structure. Primary structure—think of this as a beaded necklace, just a sequence of amino acids. Secondary structure adds shape—so your necklace starts twisting into an alpha helix, or folding in these zigzag beta sheets. I always flash back to Dr. Rosario getting tangled in his microphone cable, demonstrating helices and folds. Classic.

Avery Lin

I loved that analogy! Then we step up to tertiary structure, which is like taking those coils and folds and twisting them all together—getting that complex, 3D, functional protein ball. Usually, most proteins we use day-to-day, like enzymes, reach at least this level. And then there’s quaternary structure—the bonus round. That’s when two or more polypeptide chains come together. Hemoglobin is the big example: it acts kind of like a literal claw machine, grabbing oxygen and transporting it through your blood. It’s that multichain interaction that lets hemoglobin do its thing.

Eric Marquette

Yeah, and you don’t always get quaternary structure—single-chain proteins won’t have it, but for multi-chain ones, it’s vital. So every time you breathe or move, thank a quaternary-structured protein! All this folding magic is why the structure of a protein completely determines its function. Mess up even a little, and, well, things can go very wrong.

Avery Lin

And it all comes down, again, to how structure supports function. All right—ready to unravel even more cell mysteries?

Avery Lin

Let’s do it! So… what I always find hilarious is that textbook diagrams show this so-called “generalized cell”—a perfect circle with labeled blobs. But, have you ever seen an actual cell under a microscope? They look nothing like the books! We’ve got red blood cells that are donut-y, skin cells that are cubes, muscle cells that are ridiculously long, and neurons… well, like alien spaghetti.

Eric Marquette

Yeah, if real cells looked like the textbook average, we’d all be walking cartoons. But those diagrams still help, since they pull together the core features we need to recognize—and let us compare how cells specialize for their unique jobs. It’s that structure-meets-function thing again.

Avery Lin

Exactly. And the first barrier between “outside” and “inside” is the cell’s plasma membrane. I love Dr. Rosario’s cable analogy for this: imagine molecules with water-loving (hydrophilic) heads pointing out and water-fearing (hydrophobic) tails tucked safely away inside the “sandwich.” That’s the phospholipid bilayer—no energy needed, it just forms naturally if you gather enough phospholipids in one place. Free self-assembly—nature’s lazy genius.

Eric Marquette

It is genius! The membrane’s unique setup—hydrophilic heads on both sides, hydrophobic tails sandwiched in the middle—creates a selectively permeable barrier. It lets in what your cell needs, keeps out the riff-raff, and embeds proteins and cholesterol to adjust its properties. Also, the heads are charged, which attracts them to all the watery fluid, while the tails are nonpolar, so they hide out from water. That’s crucial for cell survival—anything that permanently slips between those tails has to be hydrophobic, like cholesterol.

Avery Lin

Little biochemistry tip for folks who love labels: “extracellular” means outside the cell, “intracellular” means inside. I mix those up way too often in my notes, so that’s your free flashcard for the week.

Eric Marquette

And inside? Most of it is water! The main spaces are the cytoplasm (fluid plus organelles) and the cytosol, which is just the fluid. Oh, and the nucleus gets its own suite, not even counted within cytoplasm. But before we zoom in on organelles, let’s talk about a story that always makes me pause: the story of HeLa cells and Henrietta Lacks.

Avery Lin

That story still gives me chills. The line between scientific advancement and ethics can get seriously blurry. Henrietta Lacks was treated for cervical cancer in the 1950s, and, without her knowing or consenting, scientists took her cells—they just didn’t die, unlike most cell samples. These so-called HeLa cells multiplied endlessly, fueling some of the biggest medical breakthroughs ever, like the polio vaccine. But for decades, her family never knew. The medical world kept benefiting, while the Lacks family wasn’t even informed. Now, every time I study a generic “cell,” I remember that behind all this science, there are real people and stories that demand respect and reflection.

Eric Marquette

It’s a powerful reminder. Progress in biology isn’t just molecules and membranes—it’s people, histories, ethics—all tangled together. All right, Avery, ready to do a tour of the cell? Because those cartoon diagrams are about to come alive with organelles.

Eric Marquette

Absolutely. Ok, so let’s start with the most hyped—mitochondria! The classic “powerhouse” line is famous for a reason. Mitochondria take in sugars like glucose and crank out ATP, the cell’s main energy currency. But here’s what’s cool: it’s the folds—the cristae—inside the mitochondria that make this all possible. The inner membrane folds over and over, packing a ton of machinery into a tiny space. The more folds, the more spots for energy reactions. Need more energy? Add more folds. Actually kind of like how your brain crams in gray matter with all those convolutions—you get more action in less room.

Avery Lin

Nature really loves maximizing surface area, right? Whether it’s your gut, the lung’s alveoli, or here in mitochondria, folds everywhere! And, when it comes to efficiency, nothing beats the cristae at loading in those ATP factories. By the way, anyone else picture a “hot dog with mustard” every time they see a mitochondrion? Dr. Rosario totally ruined me for textbook diagrams.

Eric Marquette

Guilty as charged. After you see it, you really can’t unsee it. So after mitochondria, let’s talk ribosomes—the tiny 3D printers of the cell. They take info from messenger RNA and string together the primary structure of proteins, one amino acid at a time. Most are either hanging out solo in the cytosol or studded all over the rough endoplasmic reticulum—“rough” literally because of the ribosomes stuck on the surface.

Avery Lin

And that brings us to the ER! So, rough ER is for protein assembly—tons of it in those antibody-churning immune cells and liver cells. Then there’s smooth ER, which does more with lipids and glycogen metabolism—plus it morphs into the sarcoplasmic reticulum in muscle cells. That’s a sneak peek for future muscle geek-outs.

Eric Marquette

Oh, and the proximity of rough ER to the nucleus isn’t an accident. The DNA lives in the nucleus, messenger RNA hops right out to the ribosomes across the hall—shortest distance for maximum productivity. What’s your take on the Golgi apparatus, Avery? I always imagine it as post-production at a media studio—taking raw footage, editing, labeling, packaging, and mailing it off exactly where it needs to go.

Avery Lin

That’s spot on! The Golgi is like the cell’s dispatch center—sorting, modifying, packaging up proteins into vesicles. It slaps on destination labels—maybe those proteins need to be exported out of the cell, delivered to a specific compartment, or even help grow the cell’s membrane.

Eric Marquette

And to finish off our organelle parade, let’s hit my favorite analogy—the cell skeleton! Your cell has “bones” and “muscles” too: microtubules provide strength and support, while microfilaments create movement. A mnemonic I heard in class: “microfilaments = muscles and movement, microtubules = bones for structure.” Took me too many flashcards to finally stick that in my brain.

Avery Lin

I use that too! It’s such a lifesaver during exam time. And you know, it kind of ties everything together: cell function is all about specialized structure, right down to the organelles and even their placement in the cell. This is basically Biology’s greatest hits album, and every part plays its role so precisely.

Eric Marquette

Absolutely. And, as Dr. Rosario would say, “if you know your organelles, you’re already halfway to understanding physiology.” Let’s wrap things here for today—this was such a packed episode. Avery, any last words for our anatomy crew?

Avery Lin

Just that biology is a blend of chemistry, history, and a bit of humanity—so don’t be afraid to dig into the details, and always remember there’s a story behind every “textbook diagram.” I can’t wait to keep peeling back more layers with you all next time.

Eric Marquette

Glad to have you on this journey, Avery—and thanks to everyone for tuning in. Until next week, take care, review your organelles, say hi to your mitochondria, and we’ll see you in the next one. Bye, Avery!

Avery Lin

Bye Eric! Bye everyone!