3 The Cell
3.1 Organelles: The Cell’s Structures
Cells share the same basic structure, which is left over from the time they likely originated as oil droplets in the ocean. They have various organelles, which you can think of to cells like our organs are to us, distinct parts of the cell’s “body” (it’s literally called that) with different functions.:
- A continuous cell membrane, which acts as a barrier to everything outside of the cells, and has its own
- A nucleus: a (literally) centrally located and (figuratively) central control unit that contains the DNA, which prints the instructions for synthesizing proteins, but does not actually synthesize them.
- Mitochondria: The powerhouse of the cell, and the site of cellular respiration where energy is produced from nutrients.
- Ribosomes are where the proteins are actually made. Proteins are little machines that do everything in cells. That’s why you need to eat your protein!
- Cytoplasm is the salty, viscous medium in which cellular processes take place. It’s the fluid the cell is full of.
- Vacuoles store essentials for the cell as well as waste for disposal. Also provide pressure in plant cells.
These components work, look, and interact differently in prokaryotes and eukaryotes (and inside the eukaryotes, plant cells are quite different from animal cells even though they are both eukaryotes). Here are diagrams of each illustrating the different organelles in both:
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You don’t need to know all of these for the NY Regents Exam. What you should know is that plant cells have two organelles that animals never have (prokaryotes can have them as well, especially cell walls, which all prokaryotes have):
- The cell wall: a hard surface surrounding the cell membrane, protecting it from damage and providing support.
Do not confuse the capsule of prokaryotes, which is a slimy coat that surrounds the cell wall, with their cell membrane, which is always underneath the cell wall’s protective hard material.
- Chloroplasts: organelles belonging to plants and some prokaryotes that synthesize food for the cell using photosynthesis.
Do not confuse the roles of chloroplasts and the mitochondria. Chloroplasts make the food from sunlight through photosynthesis. Plants still have mitochondria like we do to break down the food into energy for the cell.
3.2 The Memory Palace Technique
In this section, we will explore a powerful mnemonic strategy known as the memory palace technique to help you memorize the various cell processes. This technique involves visualizing a familiar place and associating different pieces of information with specific locations within that place. Let’s take a journey through our imaginary palace, where each room or location will represent a different cell process.
Memory Palace Layout:
Entrance Hall – Diffusion and Osmosis
Living Room – Active Transport
Kitchen – Cellular Respiration
Sunroom – Photosynthesis
Library – Cell Division (Mitosis and Meiosis)
1. Entrance Hall: Diffusion and Osmosis
Diffusion: As you step into the entrance hall, imagine it filled with people (molecules) randomly moving about. Over time, these people spread out evenly across the room, symbolizing the movement of molecules from an area of high concentration to low concentration, which is diffusion.
Osmosis: In the center of the hall, visualize a large aquarium divided by a semi-permeable membrane. Water flows from the less concentrated side to the more concentrated side, representing osmosis, the diffusion of water through a membrane.
2. Living Room: Active Transport
Active Transport: Moving into the living room, picture doormen actively carrying packages (molecules) against a current, up a flight of stairs. These doormen need energy (ATP) to move the packages from a low concentration to a high concentration, illustrating active transport.
3. Kitchen: Cellular Respiration
Glycolysis: Imagine chefs in the kitchen breaking down large sugar crystals (glucose) into smaller pieces (pyruvate) on the countertop, releasing a bit of energy (ATP) in the process. This represents glycolysis, the first step of cellular respiration occurring in the cytoplasm.
Krebs Cycle: Visualize a large pot on the stove where ingredients (acetyl-CoA) are continuously added and processed, releasing more energy and other products (ATP, NADH, FADH2). This is the Krebs cycle happening in the mitochondria.
Electron Transport Chain: See an assembly line of cooks passing along plates (electrons) to the end of the counter, where a generator (ATP synthase) is producing lots of energy (ATP). This represents the electron transport chain in the inner mitochondrial membrane.
4. Sunroom: Photosynthesis
Light Reactions: In the bright sunroom, sunlight streams in, hitting solar panels (chlorophyll) on the walls. These panels convert light energy into chemical energy (ATP and NADPH), symbolizing the light-dependent reactions of photosynthesis occurring in the thylakoid membranes.
Calvin Cycle: In the corner of the sunroom, see plants growing in pots using the energy from the light reactions to convert carbon dioxide (CO2) into glucose. This represents the Calvin cycle in the stroma of the chloroplasts.
5. Library: Cell Division (Mitosis and Meiosis)
Mitosis: In the library, books (chromosomes) are being carefully copied and split into two identical sections. Librarians (spindle fibers) ensure each new library (daughter cell) gets an exact set of books. This is mitosis, the process of cell division for growth and repair.
Meiosis: Imagine two separate reading rooms where books are mixed and halved (recombination and segregation). Each room ends up with a unique collection of books (haploid cells), symbolizing meiosis, the process of cell division for sexual reproduction resulting in genetic diversity.
3.2.1 Summary
By associating each cell process with a distinct location and activity in your memory palace, you can create strong mental images that enhance recall. Here’s a quick summary of the memory palace:
Entrance Hall: Diffusion and Osmosis
Living Room: Active Transport
Kitchen: Cellular Respiration (Glycolysis, Krebs Cycle, Electron Transport Chain)
Sunroom: Photosynthesis (Light Reactions, Calvin Cycle)
Library: Cell Division (Mitosis and Meiosis)
Walking through these rooms in your mind helps reinforce the processes, making them easier to remember. This technique is particularly useful for mastering the complex concepts in biology.