Embryonic Tissues, Cytoskeleton, Organelles, Cellular Energy, and DNA/RNA
Primary Embryonic Tissues and Their Development
Name the three primary embryonic tissues. What tissues does each of these eventually form as the fetus develops?
- Ectoderm: The outermost layer, forms the skin and nervous system.
- Endoderm: The innermost layer, responsible for the gut and related organs (liver, pancreas, lungs).
- Mesoderm: The middle layer, forms muscles, skeleton, blood vessels, and connective tissues. It holds everything together inside and is made up of ectoderm and endoderm.
Four Categories of the Cytoskeleton
Detail the four categories of the cytoskeleton.
- Microtubules: The largest, hollow structures (tubes) used for cell motion. They contain tubulins and are shaped like a tube. They are involved in flagella movement, maintaining structure, and intracellular transport.
- Microfilaments: The smallest, solid rods composed of actin (which causes muscle contraction). They control the membrane, cell movement, change cell shape, and elongate/contract.
- Intermediate Filaments: Intermediate in size, found in epithelia (wear and tear tissues), such as the esophagus, because it takes abuse and can build up. Formerly called tonofilaments, they reinforce cells and organize cell tissues.
- Microtrabecular Lattice: A combination of microtubules, microfilaments, and intermediate filaments, and how they are grouped/put together. They run along this lattice like train tracks, directing things along the cell. It is the internal framework of a cell.
Organelle Structure and Function
Describe the structure and function of each of the organelles discussed in the lecture.
- Cytoskeleton: Composed of four distinct elements: microtubules, microfilaments, intermediate filaments, and the microtrabecular lattice. It provides the framework for the cell.
- Centrosome: The central body or hub of the cell.
- Centrioles: Made up of microtubules that extend to make flagella. They are also the structures that move to the sides and pull protozoa (chromosomes) apart during cell division. They are important in mitosis.
- Vesicles: Released by the Golgi apparatus, vesicles have a membrane. They are temporary structures that are made and used for transport, excretion, and absorption.
Three Forms of Endocytosis
- Endocytosis: “Cell eating” – bringing particles into the cell (energy inefficient).
- Pinocytosis: “Cell drinking” – the cell membrane is lipid-based and doesn’t allow water in (energy inefficient).
- Receptor-Mediated Endocytosis: Selective (energy efficient) – the cell membrane has receptors looking for certain things. It saves energy by not taking in random particles.
Exocytosis
What is exocytosis?
Exocytosis involves taking particles and vesicles out of the cell. Coated vesicles have a specific designation. It doesn’t necessarily mean they get thrown away; exocytosis can deliver them to where they are meant to go. It is a form of excretion.
Cellular Energy: Glycolysis, Citric Acid Cycle, and Electron Transport
Detail and compare the energy yield of glycolysis, the citric acid cycle, and the electron transport system. Of what importance are the electron carriers?
Very little energy is used to get started. Electron carriers are utilized until the electron transport system manufactures ATP molecules.
- Glycolysis: Anaerobic process. Activation requires 2 ATP, which will generate energy to create 4 ATP (2 extra). The outcome is 2 ATP, 2 NADH, and 2 pyruvic acid (must have O2). It uses glucose (C-C-C-C-C-C) and pulls energy from bonds to form ATP molecules.
- Krebs Cycle (Citric Acid Cycle): Produces 8 NADH, 2 FADH2, 2 ATP, and 6 CO2.
- Electron Transport Chain (ETC): Produces 34 ATP in the liver and heart, and 32 ATP in all other cells due to the higher energy of activation.
DNA and RNA Processes
DNA/RNA
DNA -> mRNA (Messenger/Transcription) -> rRNA (Ribosomal/Codon) -> tRNA (Translation/Anticodon) -> Protein
- DNA 5′-3′ -> mRNA (switch T to U) -> tRNA (opposite of mRNA)
- rRNA (opposite of DNA 5′-3′)
- DNA 3′-5′ -> mRNA (opposite of DNA 3′-5′)