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Lecture 17 Nucleus pp91-95. Nucleus Chinese hamster ovary cells.

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Presentation on theme: "Lecture 17 Nucleus pp91-95. Nucleus Chinese hamster ovary cells."— Presentation transcript:

1 Lecture 17 Nucleus pp91-95

2 Nucleus Chinese hamster ovary cells

3 Nucleus Largest organelle Usually visible with the light microscope Spherical – elliptical shape ~ 5 um in diameter Double membrane surrounding the chromosomes & nucleolus Most cells only have 1 nucleus

4 Exceptions: Anulclear – no nucleus – mature red blood cells Multinuclear – several nuclei (2-50) – liver cells, skeletal muscle cells, platelet producing cells, bone- dissolving cells

5 Nucleus Contains nuclear envelope, nucleoli, chromatin, and distinct compartments rich in specific protein sets Gene-containing control center of the cell Contains the genetic library with blueprints for nearly all cellular proteins Dictates the kinds and amounts of proteins to be synthesized

6 Nucleus Figure 3.28a

7 4.6 The nucleus is the cell’s genetic control center The nucleus controls the cell’s activities and is responsible for inheritance –Inside is a complex of proteins and DNA called chromatin, which makes up the cell’s chromosomes –DNA is copied within the nucleus prior to cell division Copyright © 2009 Pearson Education, Inc.

8 4.6 The nucleus is the cell’s genetic control center The nuclear envelope is a double membrane with pores that allow material to flow in and out of the nucleus –It is attached to a network of cellular membranes called the endoplasmic reticulum Copyright © 2009 Pearson Education, Inc.


10 Two membranes of nuclear envelope Nucleus Nucleolus Chromatin Pore Endoplasmic reticulum Ribosomes

11 Nuclear Envelope Selectively permeable double membrane barrier containing pores Encloses jellylike nucleoplasm, which contains essential solutes

12 Nuclear Envelope Outer membrane is continuous with the rough ER and is studded with ribosomes Inner membrane is lined with the nuclear lamina, which maintains the shape of the nucleus Pore complex regulates transport of large molecules into and out of the nucleus

13 © 2013 Pearson Education, Inc. Nucleoli Dark-staining spherical bodies within nucleus Involved in rRNA synthesis and ribosome subunit assembly Associated with nucleolar organizer regions – Contains DNA coding for rRNA Usually one or two per cell

14 © 2013 Pearson Education, Inc. Figure 3.29b The nucleus. Fracture line of outer membrane Nuclear pores Nucleus Surface of nuclear envelope. Nuclear pore complexes. Each pore is ringed by protein particles. Nuclear lamina. The netlike lamina composed of intermediate filaments formed by lamins lines the inner surface of the nuclear envelope.

15 © 2013 Pearson Education, Inc. Chromatin Threadlike strands of DNA (30%), histone proteins (60%), and RNA (10%) Arranged in fundamental units called nucleosomes Histones pack long DNA molecules; involved in gene regulation Condense into barlike bodies called chromosomes when cell starts to divide

16 © 2013 Pearson Education, Inc. Figure 3.30 Chromatin and chromosome structure. 1 DNA double helix (2-nm diameter) Histones 2 Chromatin (“beads on a string”) structure with nucleosomes Linker DNA Nucleosome (10-nm diameter; eight histone proteins wrapped by two winds of the DNA double helix) 3 Tight helical fiber (30-nm diameter) 4 Looped domain structure (300-nm diameter) 5 Chromatid (700-nm diameter) 6 Metaphase chromosome (at midpoint of cell division) consists of two sister chromatids

17 Nucleic Acids Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus Their structural unit, the nucleotide, is composed of N-containing base, a pentose sugar, and a phosphate group

18 Nucleic Acids Five nitrogen bases contribute to nucleotide structure – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U) Two major classes – DNA and RNA

19 Deoxyribonucleic Acid (DNA) Double-stranded helical molecule found in the nucleus of the cell Replicates itself before the cell divides, ensuring genetic continuity Provides instructions for protein synthesis

20 Structure of DNA Figure 2.22a

21 Structure of DNA Figure 2.22b

22 Ribonucleic Acid (RNA) Single-stranded molecule found in both the nucleus and the cytoplasm of a cell Uses the nitrogenous base uracil instead of thymine Three varieties of RNA: messenger RNA, transfer RNA, and ribosomal RNA

23 Adenosine Triphosphate (ATP) Source of immediately usable energy for the cell Adenine-containing RNA nucleotide with three phosphate groups

24 Adenosine Triphosphate (ATP) Figure 2.23


26 Thank you

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