Cell Structure and Function

1. Cell Structure and Function • What color are cells in the body? • clear

2. Functions of the Cell • Basic unit of life • Protection and support • Movement • Communication • Cell metabolism and energy release • Inheritance

4. Cell Characteristics • Plasma (cell) Membrane • Outer cell boundary • Cytoplasm • Composed of cytoplasmic organelles • ER, ribosomes, centrioles, mitochondria, Golgi complex, lysosomes and vacuoles • Organelles • Specialized structures that perform specific functions

5. Plasma Membrane • Intracellular versus extracellular • Selectively permeable • Fluid-mosaic model: regulate the passage of nutrients and waste • Composed of proteins and lipids

6. Nucleus • DNA dispersed throughout; controls and integrates the function of the entire cell • Consists of : • Nuclear envelope: Separates nucleus from cytoplasm and regulates movement of materials in and out • Chromatin: Condenses to form chromosomes during cell division • Nucleolus: Assembly site of large and small ribosomal units where rRNA is manufactured

7. Cytoplasm • Cellular material outside nucleus but inside plasma membrane • Cytosol: Fluid portion • Cytoskeleton: Supports the cell • Microtubules • Microfilaments • Intermediate filaments • Cytoplasmic inclusions

8. Organelles • Small specialized structures for particular functions • Most have membranes that separates the interior of organelles from cytoplasm • Related to specific structure and function of the cell

9. Ribosomes • Sites of protein synthesis • Composed of a large and small subunit • Types • Free • Attached to endoplasmic reticulum • Found in both eukaryotes and prokaryotes

10. Endoplasmic Reticulum • Extension of outer nuclear membrane • Types • Rough • Attached ribosomes • Proteins produced and modified for secretion and for internal use • Smooth • No attached ribosomes • Manufacture lipids • Cisternae: Interior spaces isolated from rest of cytoplasm • Transports nutrients to the nucleus and provides some cell structure

11. Golgi Apparatus • Modification, packaging, distribution of proteins and lipids for secretion or internal use produced by ER • Flattened membrane sacs stacked on each other

12. Function of Golgi Apparatus

13. Mitochondria • Provide energy for cell • Major site of ATP synthesis • Membranes • Crista: Infoldings of inner membrane • Matrix: Substance located in space formed by inner membrane

14. Centrioles • In specialized zone near nucleus: Centrosome • Each unit consists of microtubules • Before cell division, centrioles divide, move to ends of cell and become spindle fibers in eukaryotic cells

15. Cilia • Appendages projecting from cell surfaces • Capable of movement • Moves materials over the cell surface

16. Flagella • Similar to cilia but longer • Usually only one exists per cell • Move the cell itself in wavelike fashion • Example: Sperm cell

17. Microvilli • Extension of plasma membrane • Increase the cell surface • Normally many on each cell • One tenth to one twentieth size of cilia • Do not move

18. Prokaryotes • Simple cells which lack a membrane bound nucleus • Initial or primitive cell type found on earth • Less complex than eukaryotes • Have no organelles (microtubules or centrioles) • Examples include bacteria • Division is by binary fission

19. Eukaryotes • Evolved from prokaryotes; they have a true nucleus • Structurally and biochemically more complex • Examples include protozoa, fungi, algae, plant and animal cells • Golgi apparatus is the structure in eukaryotic cells which secretes substances

20. Viruses • Acellular: neither prokaryotic or eukaryotic • Contain nucleic acid and either RNA or DNA but not both • Depend on the energy of the host cell • Has protective coat which makes them hard to control; antibiotics have no effect • Bacteriophage: virus which invades bacteria • Examples of viral diseases: measles, chickenpox, mumps, mono, hepatitis, AIDs

21. Overview of Cell Metabolism

22. Movement through the Plasma Membrane • Four different modes • Directly through the plasma membrane • Small, uncharged, hydrophobic molecules • Osmosis • Membrane channels • Rapid movement of water, charged small molecules • Carrier molecules • Large polar molecules that are not lipid soluble • Glucose • Vesicles • Large non-lipid soluble molecules, small pieces of matter, whole cells • Small sac surrounded by membrane

23. Movement through the Plasma Membrane • Diffusion • Osmosis • Filtration • Mediated transport mechanisms • Facilitated diffusion • Active transport • Secondary active transport

24. Diffusion • Movement of solutes from an area of higher concentration to lower concentration in solution • Only applies to small, hydrophobic, uncharged molecules • Factors that influence rate of diffusion • Temperature of solution • Distance • Size of diffusing molecules • Concentration or density gradient • Difference between two points • Viscosity • How easily a liquid flows

25. Osmosis • Diffusion of water (solvent) across a selectively permeable membrane (water most abundant compound in cell) • Important because large volume changes caused by water movement disrupt normal cell function • Cell shrinkage or swelling • Isotonic: equal concentration on both sides • cell neither shrinks nor swells • Hypertonic: Less water/more solute than other side • cell shrinks (crenation) • Hypotonic: More water/less solute than other side • cell swells (lysis)

26. Osmosis • Osmotic pressure – force required to prevent the movement of water a solution by osmosis across a selectively permeable membrane • The greater the concentration of the solution (the more hypertonic the solution) the greater the osmotic pressure • The greater the osmotic pressure the greater the tendency for water to move into the solution

27. Osmosis

28. Filtration • Works like a sieve • Depends on pressure difference on either side of partition • Moves from side of greater pressure to lower • Example: In kidneys in urine formation

29. Osmosis