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Understanding Cell Structure and Function

A cell is the smallest unit capable of life functions, with animal cells possessing a nucleus and being more complex than prokaryotic cells. Prokaryotic cells lack a membrane-bound nucleus, while eukaryotic cells include animal and plant cells. Eukaryotic cells have a membrane-bound nucleus and organelles, such as mitochondria and ribosomes. Cells also contain organic molecules like proteins, carbohydrates, lipids, and nucleic acids, each serving different functions. The cell structure includes a plasma membrane, nucleus, and cytoplasm, with organelles like mitochondria and ribosomes performing essential roles.

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Understanding Cell Structure and Function

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  1. Cell Structure & Function

  2. Definitionof Cell A cell is the smallest unit that is capableof performing life functions.

  3. “Typical” AnimalCell http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

  4. Cells cells -possessa membrane-boundnucleus -are morecomplex than prokaryoticcells -compartmentalize many cellular functions within organelles and the endomembrane system -possess a cytoskeleton for support and to maintain cellularstructure 4

  5. Cell types • Cell components: • Membrane – boundary • Cytoplasm – contains organelles • Nucleus – contains DNA • Cells types: • Prokaryotic cells: bacteria • Do not have nucleus, however, have DNA • 10x smaller Eukaryotic cells: • Animal cells • Plant cells •

  6. Two Types of Cells Prokaryotic Cells: Have no membrane covered nucleus Have no membrane - covered organelles Have circular DNA Are bacteria

  7. Figure 3.5 – prokaryotic cell This figure shows the generalized structure of a prokaryotic cell.

  8. Two Types of Cells Eukaryotic Cells: Have a nucleus Have a membrane - covered organelles Have linear DNA Are all other cells

  9. Eukaryotic cell • Components: 1. Plasma Membrane - And a Cell wall in plants, yeast 2. Nucleus 3. Cytoplasm • Organelles: • Mitochondria • Ribosomes • Endoplasmic reticulum • Golgi apparatus • Lysosomes • Peroxisomes • Cytoskeleton • Vacuoles (plants) • Chloroplast (plants)

  10. EukaryoticCells 1 0

  11. Cells Nucleus -storesthe geneticmaterial of the cell in the formof multiple, linear chromosomes -surroundedby a nuclearenvelope composed of 2 phospholipidbilayers -in chromosomes – DNA is organizedwith proteinsto formchromatin 1 1

  12. Cells 1 2

  13. Cells Ribosomes -the site of proteinsynthesisin the cell -composedof ribosomal RNA and proteins -found within the cytosolof the cytoplasm and attached to internalmembranes 1 3

  14. Organic molecules of Cells Proteins Carbohydrates Lipids Nucleic acids

  15. Proteins Most diverse and complex macromolecules in the cell Used for structure, function and information Made of linearly arranged amino acid residues

  16. Types of Proteins 1) Enzymes – catalyzes covalent bond breakage or formation 2) Structural – collagen, elastin, keratin, etc. 3) Motility – actin, myosin, tubulin, etc. 4) Regulatory – bind to DNA to switch genes on or off 5) Storage – ovalbumin, casein, etc. 6) Hormonal – insulin, nerve growth factor (NGF), etc. 7) Receptors – hormone and neurotransmitter receptors 8) Transport – carries small molecules or irons 9) Special purpose proteins – green fluorescent protein, etc.

  17. Lipids Hydrophobic molecules Energy storage, membrane components, signal molecules Triglycerides (fat), phospholipids, waxes, sterols Carbohydrates • Sugars, storage (glycogen, starch), Structural polymers (cellulose and chitin) • Major substrates of energy metabolism

  18. Nucleic Acids DNA (deoxyribonucleic acid) and RNA encode genetic information for synthesis of all proteins Building blocks of life

  19. Ribosomes Site where proteins are made Cell parts are made of proteins “Factories of the cell”

  20. Cell Structure • All Cells have: –an outermost plasma membrane –genetic material in the formof DNA –cytoplasm with ribosomes

  21. Cell Parts Organelles

  22. Surroundingthe Cell

  23. 1. Plasma Membrane • All membranes are phospholipidbilayers with embedded proteins • The outerplasma membrane –isolates cell contents –controls what gets in and out of the cell –receives signals

  24. Plasma membrane • Components: • Lipids • • Double layer of phospholipids and cholesterol & other lipids Proteins Carbohydrates • Attached to either lipids or proteins • • • Function • Allows selective passage in & out the cell

  25. Figure 3.8 – plasma membrane The plasma membrane is a phospholipid bilayer with embedded proteins. There are other components, such as cholesterol and carbohydrates, which can be found in the membrane in addition to phospholipids and protein.

  26. Plasma membrane functions • It is a boundary of the cell with many functions: • Selective permeability – allow some substances in and out the cell • Immunity – distinguish between “self” and “non-self” • Blood transfusion • Organ transplant • Viral/ bacterial infection • Change in shape – immune cells squeeze between the blood vessels’ cells and go to the pathogen location (skin etc.)

  27. Membrane transport • Membrane transport types: • Passive • Doesn’t use energy • Molecules are moving from high concentration to low • Active • Requires energy • Molecules are moving from low concentration to high • Done with the help of proteins called pumps

  28. Passive transport • Types of passive transport: • Diffusion – transport of substances (or solute when in solution) • Osmosis or Diffusion of water – transport of solvent molecules (water) • Facilitated diffusion – transport of solute with help from membrane proteins: • Channels • Transporters Solution = solvent + solutes

  29. Active transport • Moving molecules Against their concentration gradient; can be done only using energy (ATP). • Proteins in the membrane called pumps can use ATP to push chemicals from low concentration to high concentration. • Example: NA/K-pump

  30. CellMembrane • Outer membrane of cell that controls movement in and out of the cell • Double layer

  31. CellWall • Most commonly found in plant cells & bacteria • Supports & protects cells

  32. Cells • Structuresin all cells – Nucleus – Ribosomes – Endomembrane System • Endoplasmic reticulum– smoothand rough • Golgi apparatus • Vesicles – Mitochondria – Cytoskeleton

  33. Insidethe Cell

  34. Cytoplasm • Gel-likemixture • Surroundedby cell membrane • Containshereditary material

  35. Nucleus • Directs cell activities • Separatedfrom cytoplasm by nuclear membrane • Containsgenetic material - DNA

  36. The Nucleus The control center of the cell Contains the Cell’s DNA DNA Nucleolus Nuclear Membrane

  37. Nuclear Membrane • Surrounds nucleus • Made of two layers • Openings allow material to enter and leave nucleus

  38. Nucleolus • Inside nucleus • Contains RNA to build proteins

  39. Nucleus • Structure –Nuclearenvelope • TwoPhospholipid bilayers with protein lined pores –Each pore is a ring of 8 proteins with an opening in the center of the ring –Nucleoplasm– fluid of the nucleus

  40. Nucleus • DNA is arrangedin chromosomes –Chromosome– fiber of DNA with proteins attached –Chromatin – all of the cell’sDNA and the associatedproteins

  41. EndoplasmicReticulum • Moves materials around in cell • Smooth type: lacks ribosomes • Rough type (pictured): ribosomes embedded in surface

  42. Ribosomes • Each cell contains thousands • Make proteins • Found on ribosomes & floating throughout the cell

  43. GolgiBodies • Protein 'packaging plant' • Move materials within the cell • Move materials out of the cell

  44. Lysosome • Digestive 'plant' for proteins, fats, and carbohydrates • Transports undigested materi to cell membrane for removal • Cell breaks down if lysosome structure al is disrupted.

  45. Vacuoles • Membrane-bound sacs for storage, digestion, and waste removal • Contains water solution • Help plants maintain shape

  46. 3. Cytoplasm with ribosomes –Cytoplasm – fluid area inside outer plasma membrane and outside DNA region –Ribosomes – make proteins

  47. NUCLEUS CYTOSKELETON RIBOSOMES ROUGH ER MITOCHONDRION CYTOPLASM SMOOTH ER CENTRIOLES GOLGI BODY LYSOSOME PLASMA MEMBRANE VESICLE Fig. 4-15b, p.59

  48. Nuclearpore bilayerfacingcytoplasm Nuclearenvelope bilayerfacing nucleoplasm Fig. 4-17, p.61

  49. Structures of the Endomembrane System • Endoplasmic Reticulum(ER) –Continuouswith the outer membrane of the nuclear envelope –Twoforms - smoothand rough • Transportvesicles • Golgi apparatus

  50. Endoplasmic Reticulum (ER) –The ER is continuouswith the outer membraneof the nuclearenvelope –There are2 types of ER: • Rough ER – has ribosomes attached • Smooth ER – no ribosomes attached

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