2. Cell Structure and Function Chapter 3

3. Basic Characteristics of Cells Smallest living subdivision of the human body Diverse in structure and function Small

4. Basic Characteristics of Cells Divided into organelles –Structures and compartments in the cell –Isolation of chemical reactions –Each organelle performs a specific function

5. Each Cell Has Three Primary Regions Plasma Membrane Cytoplasm Nucleus

6. The Plasma Membrane Plasma membrane = outer casing of the cell –separates intracellular environment from the extracellular environment. Regulates movement of materials into and out of cell –a selective mechanical barrier

7. The Plasma Membrane Composed of Lipids, Proteins and Carbohydrates –Arranged in a lipid bilayer –“Fluid mosaic model”

8. Cell Membrane Components: Phospholipids one end is hydrophilic other end is hydrophobic tend to aggregate in a lipid bilayer –hydrophilic ends face outward, hydrophobic ends in the middle

9. Cell Membrane Components: Proteins Suspended in lipid bilayer May span layer or attached only to one surface Different functions

10. Types of Membrane Proteins Structural Proteins –Maintain membrane shape and integrity, movement Channel Proteins –Pore-like proteins –Enable small ions to pass Carrier proteins –Shuttle specific substances across membrane

11. Types of Membrane Proteins Enzymes –Catalyze specific reactions Receptor proteins –Bind cellular signals Signaling proteins / Recognition proteins –Enable cells to identify and interact with each other

12. Cell Membrane Components: Carbohydrates Branched polymers attached to extracellular surface Forms “sugar coating” (glycocalyx) of cells Functions –Lubricated surface –Protect underlying proteins –Cell recognition

13. The Cytoplasm

14. Cytosol semi-liquid, gel-like contains various dissolved materials, enzymes, etc. cytoskeleton = network of protein fibers throughout cytosol –structure –movement

15. Cytoplasmic Organelles: Ribosomes Large protein-RNA complexes Found free floating in cytosol or attached to endoplasmic reticulum synthesize proteins based on RNA codes

16. Cytoplasmic Organelles: Endoplasmic Reticulum (ER) Rough Endoplasmic Reticulum (RER) –Coated with ribosomes –Synthesis of proteins for: Cell membranes Interior (lumen) of membrane-bound organelles Export out of the cell

17. Cytoplasmic Organelles: Endoplasmic Reticulum (ER) Smooth Endoplasmic Reticulum (SER) –No ribosomes –Functions Lipid synthesis Ca 2+ storage Vesicular release

18. Cytoplasmic Organelles: Golgi Apparatus Stacks of flattened sacs Functions: –processes ER products into final form –sort and direct finished products to final destinations (intracellular or extracellular) –vesicles - small membrane coated chambers used to transport materials

19. Cytoplasmic Organelles: Lysosome Sac-like organelles which contain enzymes Break down large molecules –cell’s “digestive system” Destroy bacteria, old organelles, etc.

20. Cytoplasmic Organelles: Mitochondria Surrounded by two membranes Possess own DNA Power generators of the cell Convert food energy (e.g., glucose) to usable form –ATP high energy compound. major source of metabolic energy for the cell

21. The Nucleus

22. Cell's "control center" Largest organelle Surrounded by nuclear envelope Contains DNA –genetic information in form of nucleic acid polymers –instructs synthesis of proteins

23. DNA Structure Deoxyribonucleic acid Polymer of nucleotides –base + sugar + phosphate Four different bases –adenine (A), guanine (G), cytosine (C), thymine (T) –alternate in order –“Four-letter alphabet” Double helix –Two strands linked together by hydrogen bonds –Complementary sequences

24. Genes and Chromosomes Genes –sequences of DNA containing information needed to make proteins with the proper amino acid sequence DNA is wrapped around proteins to form chromosomes

25. Chromosomes 46 chromosomes per human cell 23 different types –pairs of homologous chromosomes –one of each pair inherited from each parent

26. DNA function Information in DNA used to make proteins 1.Transcription: sequence of DNA copied into an RNA (ribonucleic acid) molecule 2.Translation RNA sequence read by ribosomes to generate a protein with a specific amino acid sequence

27. Cell Reproduction Reproduction of cells (cell division) requires : –copying of the DNA (chromosomes) –distribution of chromosomes to daughter cells Two types of cell division –mitosis (most cells) –meiosis (gametes)

28. Mitosis Cells duplicate all their chromosomes One copy of each of the 46 chromosomes is distributed to each of the daughter cells.

29. Meiosis Occurs only in gametes Cells duplicate all chromosomes Cells undergo two separate divisions –each daughter cell has 23 total chromosomes Gametes combine to form a new cell (zygote) with 46 chromosomes