basic unit structure and function

Transcription

1 Chapter 3 Cells

2 Introduction The cell is the basic unit of structure and function in living things. Cells vary in their shape, size, and arrangements, but all cells have similar components with a particular function

3 COMPOSITE cells COMPOSITE or typical animal cell contains four major cell parts CELL MEMBRANE = the outer boundary of the cell CYTOPLASM = holds the cellular organelles CELLULAR ORGANELLES = perform specific functions of the cell NUCLEUS = control center of the cell

4 The Cell (Plasma) Membrane The cell membrane is a thin, dynamic membrane that encloses the cell and controls what enters and leaves the cell. Cell Membrane Structure = Fluid Mosaic Model Composed of a double layer (bilayer) of phospholipid molecules with many protein molecules dispersed within it.

5 The Plasma Membrane The surfaces of the membrane are hydrophilic due to their polar phosphate heads The internal portion of the membrane is hydrophobic due to the non-polar fatty acid tails

6 The Plasma Membrane The membrane proteins: Integral proteins extend across bilayer; most are glycoproteins; serve as channels(pores), transporters(carriers), receptors(rec. sites), or enzymes. Peripheral proteins loosely on the inner or outer surface; serve as enzymes or cytoskeletal anchors

7 Membrane Proteins

8 Membrane Proteins

9 Membrane Proteins

10 Phospholipid Bilayer

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12 Plasma Membrane

13 Membrane Junctions Tight junctions = adjacent plasma membranes bind together like a zipper. (impermeable junctions) Desmosomes = buttonlike thickenings of adjacent plasma membranes (anchoring junctions) Gap junctions = neighboring cells are connected by connexons; function to allow communication.

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16 CYTOPLASM (cytosol) The jelly-like fluid (70%) that holds the cellular organelles and occupies the space between the nucleus and the cell membrane.

17 CYTOPLASMIC ORGANELLES NUCLEUS: the central core, control center or brain of the cell The largest organelle of the cell Filled with nucleoplasm Contains 3 distinct regions A. Nuclear membrane (envelope) B. Nucleoli C. Chromatin

18 Nucleus: 3 Regions A. Nuclear membrane (or nuclear envelope) is a double membrane that separates the contents of the nucleus from the cytoplasm At various points, these two membranes fuse = nuclear pore The nuclear membrane is selectively permeable ; pores serve at sites where mrna can pass out of the nucleus during protein synthesis, and how ribosomes exit the nucleus.

19 Nuclear Membrane

20 NUCLEUS: 3 Regions 3 regions (cont.) A. Nucleoli (pl); Nucleolus (s) = a spherical body within the nucleus; Composed of RNA and proteins Function = synthesis of ribosomes

21 Nucleus: 3 Regions C. CHROMATIN = loosely coiled fibers of DNA and histone proteins present in the nucleus; Nucleosome = fundamental unit of chromatin; spherical clusters of eight histone proteins wrapped in DNA connected like beads on DNA string. These fibers of chromatin would be tightly coiled as chromosomes if the cell were preparing to divide.

22 Chromatin

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24 CYTOPLASMIC ORGANELLES RIBOSOMES: Small granules dispersed throughout the cytoplasm and on the membranes of some endoplasmic reticulum (ER) Composed of RNA and protein Function = protein synthesis

25 CYTOPLASMIC ORGANELLES ENDOPLASMIC RETICULUM (ER): Network of interconnected parallel membranes (maze), that is continuous with the nuclear membrane Two types Rough Endoplasmic Reticulum (RER) ER studded with ribosomes Function = protein synthesis Smooth Endoplasmic Reticulum (SER) Lacks ribosomes Function = lipid and cholesterol synthesis

26 Endoplasmic Reticulum

27 SER of liver helps to detoxify alcohol More someone drinks, the more SER they produce to a point Build up tolerance Damage to liver can be irreversible SER and Alcohol

28 CYTOPLASMIC ORGANELLES GOLGI APPARATUS (COMPLEX): Flattened membranous sacs ( cisternae ) arranged in stacks ( stack of pancakes ) associated with many vesicles (membrane bound sacs containing proteins); Function = modification, packaging, and transport of proteins Vesicles pinch off as secretory vesicles

29 CYTOPLASMIC ORGANELLES LYSOSOMES: Spherical membranous sacs containing digestive enzymes suicide sacs which destroy anything the cell no longer wants or needs Autolysis is the process by which worn cell parts are digested by autophagy.

30 Tay-Sach s Disease Enzyme = beta-hexosaminidase A does not break down fatty gangliosides Loss motor skills Seizures Vision and hearing loss Intellectual disability Paralysis Usually lethal

31 Pompe s Disease Enzyme in lysosome does not break down glycogen Muscle weakness Enlarged liver Heart problems Breathing problems

32 CYTOPLASMIC ORGANELLES PEROXISOMES: Membranous sacs containing oxidase enzymes Function = detoxification of harmful or toxic substances (i.e. alcohol, formaldehyde, oxygen free radicals) H 2 O 2 (peroxide) water

33 CYTOPLASMIC ORGANELLES MITOCHONDRIA: Kidney-shaped organelle whose inner membrane is folded into shelf-like partitions called cristae Powerhouse of the cell = site of cellular respiration where energy is released from glucose

34 Mitochondria Myopathy and Encephalomyopathy Mitochondria do not function properly because defective protein Low energy Free radical production Lactic acidosis Mattie Stepanek Ambassador Dies at 14 yrs

35 CYTOPLASMIC ORGANELLES CYTOSKELETAL ELEMENTS: Protein structures called microfilaments, microtubules, and intermediate filaments Form muscle and bones of the cell Can be broken down and reassembled

36 Cytoskeleton

37 MICROTUBULES STRUCTUREhollow tubes made of protein tubulin Funtion 1. Support 2. Anchorage for organelles and tracks for organelle movement 3. Play a role in mitosis

38 MICROFILAMENTS Structure solid, helical rods made of protein actin Function 1.Support 2. Movement and shape change of entire cell 3. Play important role in muscle contractions

39 Cell Membrane Surface Cilia short, hair-like cellular extensions (eyelashes); help move substances through passageways; located in lining of resp. tract and fallopian tube Modifications

40 CELL MEMBRANE SURFACE Flagella tail-like projection; only one per cell in humans; aids in cell locomotion; sperm cell MODIFICATIONS

41 Cell Membrane Surface Microvilli small, finger-like extensions of the external surface of the cell membrane; function=increase surface area; located in the lining of the digestive tract. Modifications

42 Centrosome and Centrioles Pair of microtubules located near the nucleus. Aid in movement of chromosomes during mitosis.

43 Which organelle provides energy for the cell? A. Chloroplast B. Mitochondria C. Lysosome D. Vacuole

44 Which organelle makes proteins? A. Rough ER B. Centrioles C. Lysosomes D. Ribosomes

45 Which organelle is found in large amounts in the liver where it detoxifies poisons consumed by body? A. Golgi Body B. Lysosomes C. Rough ER D. Smooth ER

46 Which cell structure controls what moves into and out of the cell? A. Cell wall B. Cell membrane C. Nucleus D. Chromatin

47 Which organelle is the packaging and shipping center? A. Rough ER B. Smooth ER C. Golgi Body

48 Which cell part provides structure and support to the cell? A. centriole B. cytoskeleton C. cytoplasm D. peroxisome