11. Cells, the Simplest Functional Units
TLDRIn this university cell biology lecture, the professor discusses the incredible diversity of cell types, sizes, shapes, and functions. He highlights unique specializations like neuron cells and egg cells. The lecture explores cell compartments, gradients between intracellular and extracellular environments, methods of molecular transport, organelle origins and behaviors, chromosome structure, cell division machinery like the mitotic spindle, and components of the dynamic cytoskeleton that generate force during division. The key concepts aim to showcase the complexity, selectivity, non-equilibrium nature, and miraculous coordinated mechanisms within and between living cells.
Takeaways
- π Cells exhibit incredible diversity in size, shape and behavior. They range from 1ΞΌm bacteria to 15cm ostrich eggs.
- π¬ A cell's genomic DNA is mostly the same across cell types. What differs is which genes are expressed to give cells specialized functions.
- πͺThe cell cytoskeleton forms dynamic microtubule structures that generate pulling and pushing forces to physically segregate chromosomes during cell division.
- 𧬠The Human Cell Atlas project aims to define all cell types in humans by analyzing single cell mRNA expression.
- π Endocytosis brings material from outside the cell inside, while exocytosis releases material from inside vesicles to the exterior.
- π Mitochondria likely evolved from ancient symbiotic bacteria that were engulfed by ancestral eukaryotic cells.
- π£ Three-parent babies have nuclear DNA from two parents and mitochondrial DNA from a third parent to avoid passing on mitochondrial diseases.
- β’οΈ Cells maintain differences in ion concentrations across membranes. This non-equilibrium state requires energy to actively transport ions.
- βοΈ Organelles like mitochondria and ER form interconnected, dynamic networks that interact to control processes like mitochondrial fission.
- 𧫠The genome is organized into chromosomes that condense and attach via kinetochores to microtubules of the mitotic spindle apparatus during cell division.
Q & A
What evidence supports the endosymbiotic theory for the origin of mitochondria?
-The evidence supporting the endosymbiotic theory includes: 1) Mitochondria have their own DNA and ribosomes, 2) The mitochondrial DNA is circular like bacterial chromosomes, 3) Mitochondria divide by fission similar to bacterial division.
How do cells communicate with each other?
-Cells communicate by secreting signaling molecules that can bind to receptors on other cells. This allows them to send signals to neighboring cells or distant cells through the bloodstream or other transport systems.
What is the purpose of generating three-parent babies?
-The purpose is to replace faulty mitochondrial DNA that causes genetic diseases. The nuclear DNA comes from two parents, while the mitochondrial DNA comes from a third healthy donor parent.
What makes up the cytoskeleton in cells?
-The cytoskeleton is made up of protein filaments including microtubules, actin filaments, and intermediate filaments. These provide structure and allow force generation and transport of cargo within cells.
How do microtubules generate force?
-Microtubules generate pushing forces when they grow against a barrier. They generate pulling forces when they rapidly disassemble while their ends remain attached to a cargo.
How does endocytosis bring material into the cell?
-The cell membrane pinches inward around the extracellular material. This forms a vesicle enclosing the material inside the cell separated from the cytoplasm by a membrane.
What is used to classify different cell types?
-The Human Cell Atlas project is classifying cell types based on their mRNA expression. This reflects differences in which genes are turned on/off.
Why can't eukaryotic cells make their own mitochondria?
-Eukaryotes lack the genes to produce all the mitochondrial proteins. Mitochondria replicate and divide during cell division to propagate. The original mitochondria were acquired from an endosymbiotic bacterium.
What maintains ion gradient differences across the cell membrane?
-The ion concentration differences between the inside and outside of cells are a non-equilibrium state. This requires active transport by membrane proteins that uses energy to pump ions against their gradients.
What is the role of the kinetochore?
-The kinetochore is a large protein structure that assembles on the centromere of chromosomes during cell division. It connects chromosomes to spindle microtubules for segregation.
Outlines
π Introduction to cells
Professor Martin introduces cells, highlighting their diversity in size, shape, and behavior. He points out that genomic DNA is the same across an organism's cells, but differences in gene expression lead to cellular specialization and diversity of function.
π Cellular specialization and communication
Cells acquire specialized properties to carry out specific functions. This extreme specialization is illustrated by neuron structure and function. For cells to communicate, they must be able to send and receive signals and molecules across membranes, which is enabled by endocytosis and exocytosis.
π Compartments within cells
Cells contain membrane-bound compartments that establish concentration gradients of ions like Na+, K+, and Ca2+. This non-equilibrium state requires energy to actively transport ions across membranes. Communication between compartments involves vesicular transport.
π― Endocytosis and exocytosis
The plasma membrane can invaginate to engulf extracellular molecules via endocytosis. Vesicles inside the cell can also fuse with the membrane to secrete contents outside through exocytosis. These processes enable cellular uptake and secretion.
π€ Compartments within compartments
Membrane-bound organelles like mitochondria represent compartments within the cell's compartments. Mitochondria have their own DNA and divide by fission like bacteria, supporting the endosymbiotic theory for their evolutionary origin.
π§ Mitochondrial structure and dynamics
Contrary to textbook depictions, mitochondria form dynamic tubular networks that interact with other organelles like the ER. The recent development of three-parent babies aims to replace faulty mitochondrial DNA that can cause genetic diseases.
π©βπ¬ Cell division machinery
The cytoskeleton, made of biopolymers like microtubules, comprises force-generating machines that dynamically assemble and disassemble. This allows formation of mitotic spindles that segregate chromosomes during cell division.
Mindmap
Keywords
π‘cell
π‘organelle
π‘membrane
π‘endocytosis
π‘exocytosis
π‘cytoskeleton
π‘mitosis
π‘chromosome
π‘kinetochore
π‘bipolar spindle
Highlights
Cells have a huge amount of diversity in size, shape and behavior
Genomic DNA is the same across an organism's cells, what's different is gene expression
Concentrations of molecules inside and outside cells are asymmetric, suggesting active transport requires energy
Endocytosis internalizes molecules into the cell, exocytosis secretes molecules outward
Mitochondria likely originated from ancient symbiosis between eukaryotic and bacterial cells
Three-parent babies have nuclear DNA from two parents, but mitochondrial DNA from a third parent
Mitochondria form interconnected tubular networks spanning the cell
The endoplasmic reticulum influences mitochondrial division
Chromosomes condense from unstructured DNA into distinct pairs during cell division
The cytoskeleton is a dynamic network of fibers that generates force in cells
Microtubules can push objects by polymerization and pull by depolymerization
The mitotic spindle apparatus segregates chromosomes using microtubule dynamics
A bipolar spindle pulls chromosomes to opposite poles during cell division
The kinetochore protein complex links chromosomes to microtubules
Single cell RNA sequencing helps identify and classify cell types
Transcripts
Browse More Related Video
5.0 / 5 (0 votes)
Thanks for rating: