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Cells and Tissues.

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Presentation on theme: "Cells and Tissues."— Presentation transcript:

1 Cells and Tissues

2 Cells and Tissues Carry out all chemical activities needed to sustain life Cells are the building blocks of all living things Tissues are groups of cells that are similar in structure and function

3 Anatomy of the Cell Cells are not all the same
All cells share general structures All cells have three main regions Nucleus Cytoplasm Plasma membrane Figure 3.1a

4 The Nucleus Control center of the cell Contains genetic material (DNA)
Three regions Nuclear envelope (membrane) Nucleolus Chromatin

5 The Nucleus Figure 3.1b

6 The Nucleus Nuclear envelope (membrane) Barrier of the nucleus
Consists of a double membrane Contains nuclear pores (relatively large) that allow for exchange of material with the rest of the cell Nucleoplasm – jellylike fluid in which the nucleoli and chromatin are suspended.

7 The Nucleus Nucleoli Nucleus contains one or more nucleoli
Sites of ribosome assembly Ribosomes migrate into the cytoplasm through nuclear pores Serve as the actual sites of protein synthesis

8 The Nucleus Chromatin Composed of DNA and protein
Present when the cell is not dividing Scattered throughout the nucleus Condenses to form chromosomes when the cell divides

9 Plasma Membrane Barrier for cell contents Double phospholipid layer
Hydrophilic heads Hydrophobic tails Also contains: proteins cholesterol glycoproteins

10 Plasma Membrane Proteins Scattered through out lipid bilayer.
Responsible for most specialized functions Enzymes Receptors, or bindings sites, for hormones Chemical messengers Most are involved in transport functions

11 Plasma Membrane Cholesterol Located in the plasma membrane
Helps to stabilize membrane Helps keep membrane fluid

12 Plasma Membrane Glycoproteins
Branching sugar groups attached to most proteins. Found on the extracellular side Gives the cell a fuzzy, sticky, sugar-rich surface Determine your blood type Act as receptors for bacteria, viruses or toxins

13 Plasma Membrane Figure 3.2

14 Plasma Membrane Specializations
Microvilli Finger-like projections that increase surface area for absorption

15 Plasma Membrane Specializations
Membrane junctions Tight junctions Impermeable junctions Bind cells together into leakproof sheets Small intestines – prevent digestive enzymes from seeping into bloodstream.

16 Plasma Membrane Specializations
Membrane junctions Desmosomes Anchoring junctions that prevent cells from being pulled apart Buttonlike Connected by fine protein filaments

17 Plasma Membrane Specializations
Membrane junctions Gap junctions Allow communication between cells Common with heart and embryonic cells. Cells are connected by hollow cylinder composed of proteins - connexons

18 Plasma Membrane Specializations
Figure 3.3

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