Basic Structure of a Cell

Transcription

1 Basic Structure of a Cell 1

2 Introduction to Cells Cells are the basic units of organisms Cells can only be observed under microscope Basic types of cells: Animal Cell Plant Cell Bacterial Cell 2

3 Number of Cells Organisms may be: Unicellular composed of one cell Multicellularcomposed of many cells that may organize 3

4 Cells May be Prokaryotic or Eukaryotic Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles Eukaryotes include most other cells & have a nucleus and membranebound organelles (plants, fungi, & animals) 4

5 Prokaryotes Nucleoid region contains the DNA Cell membrane & cell wall Contain ribosomes (no membrane) to make proteins in their cytoplasm 5

6 Eukaryotic Cell Contain 3 basic cell structures: Nucleus Cell Membrane Cytoplasm with organelles 6

7 Two Main Types of Eukaryotic Cells Plant Cell Animal Cell 7

8 Organelles Very small size Can only be observed under a microscope Have specific functions Found throughout cytoplasm 8

9 CELL WALL Cell wall Protect and support the enclosed substances (protoplasm) Resist entry of excess water into the cell Give shape to the cell 9

10 CELL WALL Cell wall Made of cellulose which forms very thin fibers Strong and rigid Found in plant cells 10

11 Cell or Plasma Membrane Cell membrane Living layer Controls the movement of materials into and out of the cell Selectively permeable 11

12 Surrounding the Cell Cell membrane Lies immediately against the cell wall in plant cells Made of protein and phospholipids Selectively permeable 12

13 Cytoplasm of a Cell Cytoplasm Jelly-like substance enclosed by cell membrane Provides a medium for chemical reactions to take place 13

14 More on Cytoplasm Cytoplasm Contains organelles to carry out specific jobs Examples: chloroplast & mitochondrion 14

15 NUCLEUS Nucleus Controls the normal activities of the cell Bounded by a nuclear membrane Contains chromosomes 15

16 More on the Nucleus Nucleus Each cell has fixed number of chromosomes that carry genes Genes control cell characteristics 16

17 Nucleolus Cell may have 1 to 3 nucleoli Inside nucleus Disappears when cell divides Makes ribosomes that make proteins 17

18 Smooth & Rough Endoplasmic Reticulum Smooth ER lacks ribosomes & makes proteins USED In the cell Rough ER has ribosomes on its surface & makes proteins to EXPORT 18

19 RIBOSOMES Small specks made of RNA. Found in cytoplasm or on the endoplasmic reticulum Makes proteins 19

20 Cell Powerhouse Mitochondrion ( mitochondria ) Rod shape Site of Cellular respiration 20

21 In Animal Cells: Mitochondria Active cells like muscles have more mitochondria Burn sugars to produce energy ATP 21

22 Plant Cell Organelles Vacuole Have a large central vacuole Surrounded by tonoplast Contains cell sap Sugars, proteins, minerals, wastes, & pigments 22

23 Chloroplast Plant Cell Organelles Contain the green pigment chlorophyll Traps sunlight to make sugars (food) Process called photosynthesis 23

24 Golgi Bodies Stacks of flattened sacs Have a shipping side & a receiving side Receive & modify proteins made by ER Transport vesicles with modified proteins pinch off the ends Transport vesicle 24

25 Contain digestive enzymes Break down food and worn out cell parts for cells Programmed for cell death (lyse & release enzymes to break down & recycle cell parts) Lysosome 25

26 LYSOSOME Small cylindrical Used during mitosis 26

27 Different kinds of plant cells Onion Epidermal Cells root hair Guard Cells Root Hair Cell 27

28 vacuole cytoplasm Animal cell mitochondrion nucleus No cell wall or chloroplast Stores glycogen in the cytoplasm for food energy glycogen granule cell membrane 28

29 Animal Cell Organelles Near the nucleus Paired structures Help cell divide 29

30 Different kinds of animal cells white blood cell red blood cell Amoeba cheek cells sperm nerve cell muscle cell Paramecium 30

31 Similarities between plant cells and animal cells Both have a cell membrane surrounding the cytoplasm Both have a nucleus Both contain mitochondria 31

32 Differences between plant cells and animal cells Animal cells Relatively smaller in size Irregular shape No cell wall Plant cells Relatively larger in size Regular shape Cell wall present 32

33 Differences between Plant Cells and Animal Cells Animal cells Vacuole small or absent Glycogen as food storage Nucleus at the center Plant cells Large central vacuole Starch as food storage Nucleus near cell wall 33

34 STRUCTURE & FUNCTION OF CELL MEMBRANE (pp ) 34

35 Structure & function of cell membranes Lipids = form foundation of membranes Separates inside of cell from outside Selectively permeable how phospholipids interact with H2O 35

36 CELL MEMBRANE AS BARRIER Phospholipids = Phosphate group + 2 fatty acids Polar head phosphate group attracted to water (hydrophilic) 2 Non-polar tails fatty acids repelled by water interior of membrane (hydrophobic) 36

37 Lipid bilayer = double layer Non-polar tails interior repels ions, polar molecules (sugars, proteins) 37

38 PROTEINS EMBEDDED IN LIPID BILAYER What keeps proteins within lipid bilayer? Some amino acids (remember, amino acids make up proteins) are polar / non polar Non polar part = attracted to the interior of lipid bilayer, but repelled by H2O on either side Polar part = attracted to H2O on either side of lipid bilayer **DUAL ATTRACTION holds protein in lipid bilayer* 38

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40 Cell Membranes Contain Different Types of Proteins 1. MARKER proteins attached to carbohydrate on cell s surface (help other cells recognize their cell type (heart, liver) 2. RECEPTOR proteins recognize and bind to specific substances 3. ENZYMES involved in important biochemical reactions 4. TRANSPORT proteins aid in the movement of substances into and out of the cell 40