Episode 8 will recap how cell organization is crucial to efficient functioning. Melanie distinguishes between prokaryotic and eukaryotic cells in domain and design.
Episode 8 will recap how cell organization is crucial to efficient functioning. Melanie distinguishes between prokaryotic and eukaryotic cells in domain and design (1:07). Ribosomes are found in all cells (2:22) and manufacturers protein. Membrane bound organelles are made of phospholipids, just like cellular membranes (2:58). Rapid fire review of common organelles in name, structure and function (3:25): Smooth ER, Rough ER, Golgi Complex, lysosome, vacuole mitochondria, and chloroplast. She shares two resources to help gain perspective on the complexity and impressive machinery of the cell - bring on the VR goggles! (6:31)
The Question of the Day (7:20) asks “Which of the six kingdoms have cells that never have cell walls?
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Hi and welcome to the APsolute Recap: Biology Edition. Today’s episode will recap Cell structure and function.
Lets Zoom out:
Unit 2 - Cell Structure and Function
Topic - 2.1 and 2.2
Big idea - Systems Interaction
The nucleus reigns supreme – or does it? Cells have a variety of shapes, sizes, and purposes. Some stick around for 30 minutes and others for 30 years. But what they all have in common is they are designed with the parts and pieces to be as efficient as possible.
Lets Zoom in:
The cell is the most basic unit of life and is one of two main types – prokaryotes and eukaryotes. Prokaryotic cells will not contain a nucleus nor will they have membrane bound organelles. These cells include the Domain Bacteria and Domain Archaea. Pro- meaning before and karyo- from colonel, or in charge – this is referencing the nucleus. Prokaryotic cells were the first to evolve in the history of life on Earth. In contrast, Eukaryotic cells will contain a nucleus and membrane bound organelles. Eu- meaning true – so these are cells with a genuine control center. These cell types are found in the Domains Protista, Fungi, Plantae and Animalia. Most protists are unicellular, but - fungi, plants and animals will have eukaryotic cells combining to form tissues, at times organs and even organ systems.
The organizational hierarchy we see with multicellular organisms is reflected in cellular organelles as well. But - Membrane bound organelles? What are those? And why don’t prokaryotes have them? Are they less important? Stay tuned.
One organelle that is found in all cell types are ribosomes. Ribosomes are made of rRNA (or ribosomal RNA) and protein. RNA is made up of nucleotides and proteins are made of amino acids. The primary role of ribosomes is to produce proteins. But we are kind of wandering into the twilight zone a bit here– What came first? The ribosome or the protein? Either way, we will revisit ribosomes in depth during the Central Dogma Episode, where DNA transcribes into RNA which translates into protein.
Ok – back to membrane bound organelles. These are structurally composed of phospholipids. Remember that macromolecule from Episode 5? Phospholipids have polar heads and non polar fatty acid tails. Because the intracellular and extracellular environments are aqueous, the membranes are bilayered with tails facing inwards. This allows certain organelles to be compartmentalized in their function.
In rapid fire – By name, structure, function - lets go over some common organelles.
The first is the endoplasmic reticulum – This is a series of folded membranes surrounding the nucleus. There are two types. The smooth ER, or SER and the RER or rough ER. The smooth ER is primarily involved in detoxification and lipid synthesis. The rough ER is named such because its studded with ribosomes. We already said that ribosomes produce proteins, so it should be no surprise that the RER is involved in this process as well. It will additionally compartmentalize the cell and be involved in intracellular transport.
Next is the Golgi Complex, also known as the Golgi Apparatus. This membrane bound organelle is a series of flattened stacks. It is involved with packaging, processing and shipping of proteins. This organelle is typically seen with vesicles adjacent or merging with it. I’ve always imagined a lava lamp when thinking of the Golgi with its outward bubbling vesicles. As soon as its packaged a product, it needs to ship it to another location. Because the nuclear membrane, ER and Golgi all interact, they are commonly referred to as the endomembrane system.
Two smaller organelles are sac structures. A Lysosome has hydrolytic enzymes and is involved in cell recycling and apoptosis, or scheduled cell death. A vacuole is sometimes larger. It has a variety of roles depending upon the cell that its found in. For example, in a plant cell, there is a large central vacuole that holds the extra water. Turgor pressure will increase as the vacuole fills with water. When vacuoles are empty in a plant cell, the plant will wilt. Paramecia can have vacuoles as well, but these are contractile vacuoles which help to regulate osmotic pressure, pumping water in and out of the cell.
Two of our organelles energy transducers that have double membranes. These are both pieces of evidence for the endosymbiosis theory. It is theorized that once upon a time these organelles were once independent prokaryotes. Not only do they have their own DNA, ribosomes, and replicate independently – but they are approximately the size of existing prokaryotic cells.
The first of these energy transducers is the mitochondria, which has a smooth outer layer and an inner layer folded into cristae. The mitochondria performs cellular respiration which produces energy for the cell. Quick pause. What would be an advantage of having a highly folded inner membrane? Remember surface area? The greater the number of folds, the more surface area there is. This means that more ATP can be synthesized by the mitochondria. The second energy transducer is the Chloroplast. Structurally, it has inner thylakoid membranes stacked into grana surrounded by liquid stroma. The purpose of the chloroplast is to perform photosynthesis, which will harness energy from the sun and store it in sugars.
If you haven’t seen it yet – watch “The Inner Life of a cell” on YouTube– it's remarkable. There is so much happening in the cell at one time and this does a great job at showing the complexities and beauty of molecular machinery. Another great perspective is the Cellscape VR Biology guided tour. Simply use the youtube app on your phone, or better yet – VR goggles – This will allow you to see the cell from the inside out and gives you an appreciation for just how grand the cellular show is.
To recap….
Living things are organized into subcellular components – all of which contribute to the function and ultimate success of the cell.
Make sure that you are reviewing several types of cellular diagrams during your studies. We need to recognize structure as well as scale when reviewing these organelles.
Today’s Question of the day is about Kingdoms.
Question: Which of the six kingdoms have cells that never have cell walls?