Organelles Ribosomes - sites of protein synthesis

Organelles Endoplasmic reticulum - network of membranes in the shape of flattened sacs or tubules - Rough ER - connected to the nuclear envelope, a series of flattened sacs, surface is studded with ribosomes, produces various proteins -Smooth ER - a network of membrane tubules, does not have ribosomes, synthesizes fatty acids and steroids, detoxifies certain drugs

Organelles Golgi complex - consists of 3–20 flattened, membranous sacs called cisternae. - Modify, sort, and package proteins for transport to different destinations. - Proteins are transported by various vesicles .

Golgi Complex

Processing and Packaging

Organelles Lysosomes - vesicles that form from the Golgi complex and contain powerful digestive enzymes

Organelles Peroxisomes Proteasomes Smaller than lysosomes Detoxify several toxic substances such as alcohol Abundant in the liver Proteasomes Continuously destroy unneeded, damaged, or faulty proteins Found in the cytosol and the nucleus

Organelles Mitochondria - the “powerhouses” of the cell Generate ATP More prevalent in physiologically active cells: muscles, liver and kidneys Have inner and outer mitochondrial membranes similar in structure to the plasma membrane Cristae - the series of folds of the inner membrane Matrix - the large central fluid-filled cavity Self-replicate during times of increased cellular demand or before cell division Contain own DNA Inherited only from your mother

Mitochondria

Organelles - Nucleus Spherical or oval shaped structure Usually most prominent feature of a cell Nuclear envelope - a double membrane that separates the nucleus from the cytoplasm Nuclear pores - numerous openings in the nuclear envelope, control movement of substances between nucleus and cytoplasm Nucleolus - spherical body that produces ribosomes Genes - the cell’s hereditary units, control activities and structure of the cell Chromosomes - long molecules of DNA combined with protein molecules

Nucleus

Packing of DNA into a Chromosome of a Dividing Cell

Overview of Gene Expression

Transcription

Translation

Translation

Translation

Translation

Translation

Translation

Translation

Translation

Protein Synthesis Interactions Animation You must be connected to the internet to run this animation.

Somatic Cell Division - Mitosis The cell cycle is a sequence of events in which a body cell duplicates its contents and divides in two Human somatic cells contain 23 pairs of chromosomes (total = 46) The two chromosomes that make up each pair are called homologous chromosomes (homologs) Somatic cells contain two sets of chromosomes and are called diploid cells

Cell Division Interphase - the cell is not dividing - The cell replicates its DNA - Consists of three phases, G1, S, and G2, replication of DNA occurs in the S phase Mitotic phase - consists of a nuclear division (mitosis) and a cytoplasmic division (cytokinesis) to form two identical cells

The Cell Cycle

DNA Replication

Nuclear Division: Mitosis Prophase - the chromatin fibers change into chromosomes. Metaphase - microtubules align the centromeres of the chromatid pairs at the metaphase plate. Anaphase - the chromatid pairs split at the centromere and move to opposite poles of the cell; the chromatids are now called chromosomes. Telophase - two identical nuclei are formed around the identical sets of chromosomes now in their chromatin form.

Cytoplasmic Division: Cytokinesis Division of a cell’s cytoplasm to form two identical cells Usually begins in late anaphase The plasma membrane constricts at its middle, forming a cleavage furrow The cell eventually splits into two daughter cells. Interphase begins when cytokinesis is complete .

Mitosis 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: Cleavage furrow (e) TELOPHASE (c) METAPHASE 2 3 4 5 Cleavage furrow (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate Chromosome all at 700x LM (two chromatids joined at centromere Centromere 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: (f) IDENTICAL CELLS IN INTERPHASE Cleavage furrow (e) TELOPHASE (c) METAPHASE Cleavage furrow 2 3 4 5 6 (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate Chromosome all at 700x LM Centromere (two chromatids joined at centromere 1 Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol (a) INTERPHASE Centrioles Centrosome: all at 700x LM 1 Early Late (d) ANAPHASE Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Chromosome (a) INTERPHASE Centrioles Centrosome: (c) METAPHASE 2 3 4 Cleavage furrow (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore Metaphase plate all at 700x LM (two chromatids joined at centromere Centromere 1 Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Metaphase plate (a) INTERPHASE Centrioles Centrosome: (c) METAPHASE 2 3 Late Early (b) PROPHASE Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore all at 700x LM Chromosome (two chromatids joined at centromere Centromere 1 Late Early Pericentriolar material Nucleolus Nuclear envelope Chromatin Plasma membrane Cytosol Chromosome (two chromatids joined at centromere (a) INTERPHASE (b) PROPHASE Centrioles Centrosome: Fragments of nuclear envelope Mitotic spindle (microtubules) Kinetochore 2 all at 700x LM Centromere Mitosis

Mitosis

Mitosis

Mitosis

Mitosis

Mitosis

Mitosis

Reproductive Cell Division During sexual reproduction, each new organism is the result of the union of two gametes (fertilization), one from each parent. Meiosis - reproductive cell division that occurs in the gonads (ovaries and testes) that produces gametes with half the number of chromosomes. Haploid cells - gametes contain a single set of 23 chromosomes. Fertilization restores the diploid number of chromosomes (46).

Reproductive Cell Division Meiosis occurs in two successive stages: meiosis I and meiosis II . Each of these two stages has 4 phases: prophase, metaphase, anaphase, and telophase. Summary - Meiosis I begins with a diploid cell and ends with two cells having the haploid number of chromosomes; in Meiosis II, each of the two haploid cells divides, and the net result is four haploid gametes that are genetically different from the original diploid starting cell.

Meiosis and Cytokinesis

Comparison of Mitosis and Meiosis

Cell Division Interactions Animation The Cell Cycle and Division Processes Interactions Animation You must be connected to the internet to run this animation.

Cellular Diversity The average adult has nearly 100 trillion cells. There are about 200 different types of cells. Cells come in a variety of shapes and sizes. Cellular diversity permits organization of cells into more complex tissues and organs.

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