from week 3 lecture 5 and 6
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| What is the Nucleus? | Relatively large, centrally located organelle. Sometimes called "brain of the cell" it is the control center involved in regulating physiological processes.
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| What is the nuclear envelope? | Double layer of membrane that surrounds the nucleus of a cell.
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| What is the job of nuclear pores? | The nucleus maintains contact with the cytoplasm by transporting materials through nuclear pores. Nuclear pores are regions with greater permeability.
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| Where is most of the DNA of a eukaryotic cell located? | The nucleus. The associated genes determine which proteins the cell can make.
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| Where is the nucleoplasm? | Inside the nucleus.
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| What is Chromatin? | Chromatin is a thread like material made up of DNA and proteins; some of which are homogeneous (all the same)and heterogeneous (of different types).
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| What are histones? | Histones are homogeneous proteins that help maintain structural stability of DNA and influence gene expression by binding with DNA in structures called nucleosomes.
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| Heterogeneous proteins include enzymes of various types and are involved in what processes? | DNA replication and transcription.
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| How are chromosomes formed? | During cell division, chromatin threads are highly folded into discrete structures called chromosomes.
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| What are Nucleoli? (singular nucleolus) | Nucleoli are dark-staining bodies sometimes visible with the nucleoplasm of certain cells.
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| What is the composition of nucleoli? | Composed of ribosomal-RNA and protein.
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| What are the "pacemakers" of the cell and why? | Nucleoli---referred to as pacemaker because they influence protein synthesis. Also the site of r-RNA synthesis and the assembly of ribosomal subunits.
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| What is the site of r-RNA synthesis and assembly of ribosomal subunits? | The nucleoli or the "pacemaker"
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| What part of the cell makes the ribosomes responsible for all protein synthesis? | The nucleoli or the "pacemaker"
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| What are Spliceosomes? | small granular bodies made up of small or short-RNA known as s-RNA. s-RNA molecules contain high amount of uracil.
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| What is the function of Spliceosomes? | The function of Spliceosomes within the nucleus is to modify RNA molecules as they are transcribed from DNA.
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| What is post-transcriptional modification? | The process that spliceosomes use to modify RNA. Involves cutting out some regions of RNA and splicing the remaining pieces together.
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| What is a microtubule? | microscopic tube-like structure made up of proteins called tubulins or tubulin proteins.
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| What is a heterodimer? | Each tubulin unit is actually a heterodimer composed of one alpha and one beta tubulin.
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| What is a protofilament? | A linear structure formed when a tubulin dimer polymerize (connect together in long chains). They each have an alpha subunit at one end and a beta subunit at the other and this orientation is significant and consistent within each microtubule.
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| What are the alpha and beta subunits called in a protofilament of a microtubule? | The beta subunit end is called the positive end and the alpha unit is called the negative end.
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| What is the wall of the typical microtubule composed of? | The wall is composed of 13 protofilaments arranged as linear strands that spiral around the tubule forming imperfect helixes. In cross section they appear as 13 globular protein dimers arranged in a circle.
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| Can microtubules be lengthened or shortened? | Yes, by adding or removing tubulin dimers and thus exsist as dynamic structures changing as necessary for cellular function. Addition of tubulin dimers happens most readily at positive end, removal at negative end.
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| What is the function of microtubules? | Microtubules function as support structures forming part of the cytoskeleton and are involved in intercellular motion.
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| What is a MAP? | Microtubule-associated proteins. proteins that interact with microtubules. Two types are; Kinesin and Dynein.
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| What is the purpose of Kinesin proteins in regards to microtubules? | kine=movement so...kinesin proteins attach to and "walk" along protofilaments toward positive end and can carry cell components such as small organelles, vesicles, and other cytoskelatal elements along the microtubule. Requires ATP as energy source.
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| What is the purpose of Dynein in regards to microtubules? | Dynein is capable of picking up and carrying things along the microtubules towards the negative end. Involved in the movement of cilia and flagella. Requires ATP as energy source.
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| What is an intercellular highway? | When kinesin and dynein are carrying materials along the microtubules in opposite direction at the same time.
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| What is cilia? | short hair like locomotor structure found on surface of some eukaryotic cells. Quite numerous/usually cover entire cell surface. Attached to basal bodies, surrounded by membrane, and supported by microtubules arranged in specific pattern.
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| What is flagella? | A locomotive structure found on surface of some eukaryotic cells. Longer and whip like, attached to basal bodies, surrounded by cell membrane and supported by microtubules in specific pattern. Cells will have only one or two.
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| What does a flagellum do? | A single flagellum can can pull a cell through its environment, or in pairs can move together like the arms of a person swimming the breaststroke. Sometimes one will pull while the other one rests.
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| What does a cilium do? | Cilia move in a highly coordinated fashion, creating wave like patterns that flow over the cell surface or rotate around food getting structures. Some move single cell organisms while others move materials. Protozoa sometimes use to push food to "mouth"
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