1 / 45

Cell Structure and Function Chapter 4 Biology 100

Cell Structure and Function Chapter 4 Biology 100. Discovery of the Cell. Robert Hooke used a simple kind of microscope to study slices of cork in 1664. He saw many cubicles fitting neatly together Hooke called these cells.

ila-farrell
Download Presentation

Cell Structure and Function Chapter 4 Biology 100

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Cell Structure and FunctionChapter 4Biology 100

  2. Discovery of the Cell • Robert Hooke used a simple kind of microscope to study slices of cork in 1664. • He saw many cubicles fitting neatly together • Hooke called these cells. • van Leeuwenhoek was the first to see living cells and later was first to see bacteria Van Leeuwenhoek’s microscope

  3. The Cell Theory • Schleiden and Schwann came up with the theory in the 1830’s • All living things are made of cells • Virchow added in 1855 to the cell theory • New cells are formed only from division of pre-existing cells, not spontaneous generation

  4. Differences and Similarities of Cells • All cells are surrounded by a plasma membrane (cell membrane) which is selectively permeable to materials. • Prokaryotes lack a true nucleus as well as internal membrane-bound organelles. • Bacteria • Eukaryotes have a true nucleus and have at least one membrane-bound organelle • Include plant, animal, fungi, protozoa and algae cells

  5. Cell Size • Prokaryotic cells can be 1-10 μm, while eukaryotic cells are 10-100 μm. • Some eukaryotic cells are quite large, like the yolk of a chicken egg • Two organelles found in eukaryotes, the mitochondrion and the chloroplast, are similar in size to most bacteria.

  6. Cell Size • The ratio of surface area to cell volume limits cell size because it reflects the balance between supply rate and supply demand. • The surface area determines the rate at which materials diffuse into or out of the cell. • For a cell of a constant shape, for every time the surface area increases by L2, volume increases L3

  7. Prokaryotes • Prokaryotes have no true nucleus or membrane-bound organelles, have a nucleoid region • Has a Cell Wall, and some may have a capsule, which encloses the cell wall • Forms of movement are the flagella and/or the pilli • Contains ribosomes where protein synthesis occurs

  8. Prokaryotes • Bacteria cells have different shapes • Rod-shape • Spherical shape • Spiral

  9. Eukaryotes • Eukaryotes, unlike prokaryotes, have a true, membrane-bound nucleus. • Contain a variety of organelles, specialized membrane-bound structures where cell processes occur

  10. Endoplasmic Reticulum • Endoplasmic Reticulum (ER) is where proteins and lipids are synthesized • Large surface area • Rough ER is embedded with ribosomes • Ribosomes are nonmembranous organelles that help with synthesis of proteins • Smooth ER is where lipids are synthesized, detox

  11. Golgi Apparatus • Golgi Apparatus are smooth, flattened membranous sacs • Collects, packages and distributes molecules manufactured in the cell • Animals contain around 20 complexes, plants have hundreds.

  12. Vesicles and Vacuoles • Tiny, membranous sacs known as vesicles deliver molecules to and from the Golgi Complex, vacuoles are larger structures that perform the same tasks • Some go from ER to the Golgi Complex • Some go to other organelles in cell • Others will go to plasma membrane and combine with it • May contain insulin, enzymes, etc. to go outside the cell • In plants, some vesicles have cellulose to make new cell wall material • Some vesicles contain enzymes to breakdown various molecules

  13. Fig. 4.11, pg. 77. Lysosome • A lysosome is a tiny vesicle that buds off the Golgi Apparatus and contains enzymes that break down macromolecules, for digestion and destruction • These enzymes function best at a pH of 5 • Hydrogen ions are transported into lysosome to create this acidic environment • Will also destroy bacteria, viruses and fungi

  14. Peroxisome • A peroxisome is an organelle that has the enzyme, catalase, that breaks down hydrogen peroxide, H2O2 • Breaks down fatty acids into 2 carbon fragments • n addition it includes enzymes which synthesize cholesterol and bile acids. • Is not formed in the Golgi apparatus • Aids chemical reactions, including the breakdown of fatty acids, synthesis of cholesterol and synthesis of lipid molecules

  15. Ribosomes • Ribosomes are constructed from two subunits, which are composed of ribosomal RNA and proteins. • Ribosomes synthesize polypeptides from free amino acids, according to the instructions on messenger RNA. • Ribosomes are like CD players, producing music (proteins) according to the instructions on the CD (mRNA).

  16. Nucleus • The nucleus is surrounded by two membranes, the nuclear envelope • Protein complexes at nuclear pores regulate the entry of large macromolecules into and out of the nucleus • The nucleus contains most of the DNA in a cell.

  17. Nucleus • The primary function of the nucleus is to transfer the information for the synthesis of proteins from DNA to RNA. • The nucleolus is a dense area within the nucleus with DNA fragments, ribosomal RNA, and proteins. • The nucleolus organizes the RNA and proteins into the ribosomal subunits.

  18. Mitochondria • Mitochondrion (singular) has two membranes • Outer membrane is relatively simple, but the inner membrane is highly folded, a structure called cristae • Cristae are rich in enzymes for electron transfer and ATP synthesis

  19. Mitochondria • The matrix is a fluid filled space inside the inner membrane • It contains soluble enzymes for aerobic cellular respiration. • The matrix also contains DNA (mtDNA), RNA, and ribosomes.

  20. Mitochondria • Known as the powerhouse of the cell • It converts the energy stored in organic molecules to forms usable to the cells, especially production of ATP • Food + O2 → CO2 +H20 + Energy (ATP)

  21. Chloroplasts • Chloroplasts are also surrounded by two membranes. • The outer and inner membranes, and intermembrane space are barriers, but play no specific functional role in photosynthesis. • Inside the inner membrane is the stroma, an aqueous space. • Floating in the stroma are thylakoids, flat membranous sac.

  22. Chloroplasts • The thylakoid membrane contains chlorophyll and other pigments, electron transfer molecules, and enzymes that trap the energy in sunlight - photosynthesis. • This energy is used to generate ATP and high energy electrons in the light-dependent phase of photosynthesis. • These molecules pass to the stroma where CO2 and H2O are converted into sugars.

  23. Chloroplasts • The stroma also contains DNA (chDNA), RNA, and ribosomes. • In the stroma, DNA is transcribed to RNA and RNA is translated into some chloroplast proteins.

  24. Cytoskeleton • Intermediate filaments are semi-permanent components of the cytoskeleton. • Intermediate filaments are semi-permanent components of the cytoskeleton. • Intermediate filaments maintain cell shape and attach to proteins in the cell membrane

  25. Cytoskeleton • Microfilaments are built with the beadlike protein actin • During cell division, motor proteins pull actin filaments together, slicing the cytoplasm in half like string around a ball of dough. • In muscle cells, the motor protein myosin pulls together microfilaments during contraction.

  26. Cytoskeleton • Microtubules are small tubes that are built with the protein tubulin. • During normal conditions, one of their functions is to act as roadways for motor proteins.

  27. Cytoskeleton • Microtubules are also the central supports for cilia and flagella. • Covered by just the cell membrane, cilia and flagella extend from the cell. • Motor proteins push/pull on the tubules within the cilium/flagellum. • This causes them to move back and forth.

  28. Cell Membranes • Phospholipids are the dominant molecule in membranes. • Phospholipids naturally assemble into a bilayer • The membrane’s center is hydrophobic because of the fatty acid tails. • The outer edges are hydrophilic because of the phosphate groups.

  29. Fluid Mosaic of Membranes

  30. Cell Transport • A membrane is a selectively permeable barrier • Single molecules that are nonpolar or only slightly polar can pass through the hydrophobic core without problems. • These include O2, N2, CO2, steroids, alcohols, fatty acids, and pesticides. • The cell cannot regulate movement of these molecules as they follow the rules of simple diffusion

  31. Cell Transport • Single molecules that are polar or charged require a transport protein or channel protein to pass through the core. • These include H20, ions, sugars, amino acids, and proteins. • Their movements into / out of the cell can be regulated by modifying the proteins involved.

  32. CellTransport • Materials can move pass membranes: • A) as single molecules (diffusion and active transport) or in large quantities (vesicular transport) • B) without input of energy (passive transport) or requiring energy (active transport) • C) without the help of a protein (simple diffusion) or with the help of a protein (facilitated and channel-mediated diffusion).

  33. Diffusion • During diffusion, molecules move from areas of higher concentration to areas of lower concentration, “down” the concentration gradient. • At equilibrium, movements of molecules in one direction are balanced by movements in the opposite direction.

  34. Diffusion • Diffusion rates depend on: • a) the distance over which molecules must move: • shorter (thinner membrane) = faster • b) the size of the molecule: • smaller = faster • c) the surface available for diffusion: • wider = faster • d) the speed that molecules are moving = temperature: • higher = faster • e) the concentration gradient between two points • greater concentration difference = faster.

  35. Diffusion • Diffusion rates also depend on how permeable the membrane is to a particular kind of molecule • The diffusion rates of one type of molecule are independent of the concentrations of any other types of molecules • In simple diffusion, molecules move past the membrane through the lipid core.

  36. Diffusion • In channel mediated diffusion, molecules pass the membrane through a protein pore.

  37. Osmosis • Osmosis is the movement of “free” water down its concentration gradient. • Some water molecules surround solutes as part of spheres of hydration. • If a membrane is not permeable to that solute, then these water molecules cannot pass either. • A solution with few dissolved molecules (low osmolarity) will have more free water molecules than a solution with more dissolved molecules (high osmolarity).

  38. Osmosis • Imagine that we have a selectively permeable membrane separating a 40% sugar solution from a 10% sugar solution. • There are more “free” water molecules on the 10% sugar side than there are on the 40% sugar side. • Because there are more “free” water molecules in the 10% side, water will move by osmosis (diffusion of water) to the 40% side.

  39. Isotonic • If the concentration of dissolved materials is equal in the surrounding solution as in the cell, then no net movement of water occurs.

  40. Hypertonic • If the concentration of dissolved materials is greater in the solution than in the cell, then water will leave the cell. The solution is hypertonic compared to the cell. • If the concentration of dissolved materials is lower in the solution than in the cell, then water will enter the cell. The solution is hypotonic compared to the cell.

  41. Transport • Specific carrier proteins allow materials that are not hydrophobic to pass through a membrane. • In facilitated diffusion, the carrier protein allows molecules to move from high concentration to low concentration. • Osmosis, facilitated diffusion, and standard diffusion are all examples of passive transport. • movement of materials down a concentration gradient without expenditure of energy

  42. Active tranpsort • Active transport is the movement of materials across a membrane against its concentration gradient. • Molecules are pumped from low concentration to higher concentration. • Active transport requires metabolic energy to do the pumping.

  43. In exocytosis a membrane-bound sac (a vesicle) fuses with a membrane and dumps the fluid contents outside the membrane (usually outside the cell). • Endocytosis is the reverse of exocytosis. • A region of membrane forms a pocket around the external materials, pinches off a vesicle, and transports this material inside. • In phagocytosis, the materials being brought insides are solid particles. • In pinocytosis, the materials being brought inside are fluids.

  44. Endocytosis and exocytosis • White blood cells actively use endocytosis and exocytosis in their role as defenders of the body from invaders. • When they detect a microbe, they extend fingers of membrane and cytoplasm to surround it. • When the membrane fingers meet, they fuse.

More Related