Chapter 4 A Tour of the Cell.

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1 Chapter 4 A Tour of the Cell

2 Biology and Society: Antibiotics: Drugs that Target Bacterial Cells
Antibiotics were first isolated from mold in 1928. The widespread use of antibiotics drastically decreased deaths from bacterial infections. Most antibiotics kill bacteria while minimally harming the human host by binding to structures found only on bacterial cells. Some antibiotics bind to the bacterial ribosome, leaving human ribosomes unaffected. Other antibiotics target enzymes found only in the bacterial cells © 2013 Pearson Education, Inc. 2

3 Figure 4.0 Figure 4.0 Two kinds of cells: Bordetela pertussis and human throat cells

4 Microscopes as Windows on the World of Cells
Organisms are either Single-celled, such as most prokaryotes and protists or Multicelled, such as plants, animals, and most fungi Cells were first described in 1665 by Robert Hooke. The accumulation of scientific evidence led to the cell theory which states that. All living things are composed of cells The cell is the basic living unit of organization for all organisms All cells come from other cells.

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6 Microscopes as Windows on the World of Cells
Light microscopes can be used to explore the structures and functions of cells. When scientists examine a specimen on a microscope slide, light passes through the specimen and lenses enlarge, or magnify, the image. Magnification is an increase in the object’s image size compared to its actual size. Resolving power is the ability of an optical instrument to show two objects as separate. © 2013 Pearson Education, Inc. 6

7 Microscopes as Windows on the World of Cells
The electron microscope (EM) uses a beam of electrons, which results in better resolving power than the light microscope. Two kinds of electron microscopes reveal different parts of cells. Scanning electron microscopes (SEM) examine cell surfaces. Transmission electron microscopes (TEM) are useful for internal details of cells. The electron microscope can Magnify up to 100,000 times Distinguish between objects 0.2 nanometers apart © 2013 Pearson Education, Inc.

8 The protists Paramecium viewed with
three different types of microscopes TYPES OF MICROGRAPHS Light Micrograph (LM) Scanning Electron Micrograph (SEM) Transmission Electron Micrograph (TEM) For viewing living things For viewing surface features For viewing internal structures Figure 4.1 Figure 4.1 The protist Paramecium viewed with three different types of microscopes

9 An electron microscope Figure 4.2 Figure 4.2 An electron microscope

10 The size range of cells 10 m Human height 1 m Length of some nerve and
muscle cells 10 cm Unaided eye Chicken egg 1 cm Frog eggs 1 mm 100 µm Plant and animal cells Light microscope 10 µm Nuclei Most bacteria Mitochondria 1 µm Smallest bacteria Electron microscope 100 nm Viruses Ribosomes 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms Figure 4.3 Figure 4.3 The size range of cells

11 LM 10 m Human height 1 m Length of some nerve and muscle cells
Figure 4.3a 10 m Human height 1 m Length of some nerve and muscle cells 10 cm Unaided eye Chicken egg 1 cm Frog eggs 1 mm LM Figure 4.3 The size range of cells (part 1)

12 100 µm Plant and animal cells Light microscope 10 µm Nuclei
Figure 4.3b 100 µm Plant and animal cells 10 µm Nuclei Light microscope Most bacteria Mitochondria 1 µm Smallest bacteria Electron microscope 100 nm Viruses Ribosomes 10 nm Proteins Lipids 1 nm Small molecules Atoms 0.1 nm Figure 4.3 The size range of cells (part 2)

13 The Two Major Categories of Cells
The countless cells on Earth fall into two basic categories: Prokaryotic cells — Bacteria and Archaea and Eukaryotic cells — protists, plants, fungi, and animals (Structural complexity inside the cell). All cells have several basic features. They are all bounded by a thin plasma membrane. Inside all cells is a thick, jelly-like fluid called the cytosol, in which cellular components are suspended. All cells have one or more chromosomes carrying genes made of DNA. All cells have ribosomes (machinery for protein ), tiny structures that build proteins according to the instructions from the DNA. © 2013 Pearson Education, Inc. 13

14 The Two Major Categories of Cells
Prokaryotic cells are older than eukaryotic cells (first cells that live on earth). Prokaryotes appeared about 3.5 billion years ago Eukaryotes appeared about 2.1 billion years ago. Prokaryotic cells are usually smaller than eukaryotic cells and simpler in structure (one cell or one compartment where they do all the things that eukaryotic cell do). © 2013 Pearson Education, Inc. 14

15 The Two Major Categories of Cells
A prokaryotic cell lacks a nucleus. Its DNA is coiled into a nucleus-like region called the nucleoid, which is not partitioned from the rest of the cell by membranes (Localized again the wall). Eukaryotes (are structurally more complex) Only eukaryotic cells have organelles, membrane-enclosed structures that perform specific functions. The most important organelle is the nucleus, which houses most of a eukaryotic cell’s DNA and is surrounded by a double membrane. © 2013 Pearson Education, Inc. 15

16 An idealized prokaryotic cell
It can of spinning like a little propeller Plasma membrane (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA) Pili (attachment structures) Colorized TEM Colorized TEM

17 CATEGORIES OF CELLS Prokaryotic Cells Eukaryotic Cells
• Smaller • Simpler • Most do not have organelles • Found in bacteria and archaea • Larger • More complex • Have organelles • Found in protists, plants, fungi, animals Figure UN12 Summary: categories of cells

18 An Overview of Eukaryotic Cells
Eukaryotic cells are fundamentally similar (but more complex inside). All contain a cell membrane The region between the nucleus and plasma membrane is the cytoplasm (cytosol + organelles). The cytoplasm consists of various organelles suspended in the liquid cytosol (semi-fluid substance). All have Chromatin which contain chromosomes which have genes in the form of DNA. 18

19 An Overview of Eukaryotic Cells
Unlike animal cells, plant cells have - chloroplasts, which convert light energy to the chemical energy of food in the process of photosynthesis, and - protective cell walls. Only animal cells have lysosomes (b/c we do digest things), bubbles of digestive enzymes surrounded by membranes BioFlix Animation: Tour Of An Animal Cell BioFlix Animation: Tour Of A Plant Cell Blast Animation: Animal Cell Overview Blast Animation: Plant Cell Overview © 2013 Pearson Education, Inc. 19

20 Not in most plant cells Idealized animal cell Not in animal cells
Figure 4.5 Ribosomes Centriole Not in most plant cells Cytoskeleton Lysosome Plasma membrane Nucleus Mitochondrion Rough endoplasmic reticulum (ER) Smooth endoplasmic reticulum (ER) Golgi apparatus Idealized animal cell Cytoskeleton Mitochondrion Central vacuole Cell wall Not in animal cells Nucleus Chloroplast Rough endoplasmic reticulum (ER) Ribosomes Plasma membrane Smooth endoplasmic reticulum (ER) Channels between cells Idealized plant cell Golgi apparatus Act like a FEDEX Figure 4.5 A view of an idealized animal cell and plant cell

21 The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins
The plasma membrane separates the living cell from its nonliving surroundings. The remarkably thin membranes of cells are composed mostly of lipids and proteins. The lipids belong to a special category called phospholipids. Phospholipids form a two-layered membrane (that act as a selective barrier), the phospholipid bilayer. Proteins (main job is to primary allow things in and out of the cell) © 2013 Pearson Education, Inc. 21

22 The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins
Most membranes have specific proteins embedded in the phospholipid bilayer. These proteins help regulate traffic across the membrane and perform other functions. Allow the passage of O2 ; nutrients and waste The plasma membrane is a fluid mosaic. Fluid because molecules can move freely past one another. A mosaic because of the diversity of proteins in the membrane. © 2013 Pearson Education, Inc.

23 (a) Phospholipid bilayer of membrane
Outside of cell Outside of cell Proteins Hydrophilic region of protein Hydrophilic head Hydrophobic tail Hydrophilic head Phospholipid bilayer Hydrophobic tail Phospholipid Cytoplasm (inside of cell) Hydrophobic regions of protein (a) Phospholipid bilayer of membrane Cytoplasm (inside of cell) (b) Fluid mosaic model of membrane Figure 4.6 Figure 4.6 The plasma membrane structure

24 Cytoplasm (inside of cell)
The plasma membrane structure Outside of cell Hydrophilic head Hydrophobic tail Phospholipid Cytoplasm (inside of cell) (a) Phospholipid bilayer of membrane Figure 4.6a Figure 4.6 The plasma membrane structure (part 1)

25 The Process of Science: What Makes a Superbug?
Observation: Bacteria use a protein called PSM to disable human immune cells by forming holes in the plasma membrane. Question: Does PSM play a role in MRSA infections? Hypothesis: MRSA bacteria lacking the ability to produce PSM would be less deadly than normal MRSA strains. Experiment: Researchers infected Seven mice with normal MRSA Eight mice with MRSA that does not produce PSM Results: All seven mice infected with normal MRSA died. Five of the eight mice infected with MRSA that does not produce PSM survived. Conclusions: MRSA strains appear to use the membrane-destroying PSM protein, but Factors other than PSM protein contributed to the death of mice

26 How MRSA may destroy human
immune cells? Colorized SEM 1 MRSA bacterium producing PSM proteins Methicillin-resistant Staphylococcus aureus (MRSA) 2 PSM proteins forming hole in human immune cell plasma membrane PSM protein Plasma membrane Pore 3 Cell bursting, losing its contents through the holes Figure 4.7a-3 Figure 4.7 How MRSA may destroy human immune cells (step 3)

27 Cell Surfaces Plant cells have rigid cell walls surrounding the membrane. Plant cell walls are made of cellulose, protect the cells, maintain cell shape, and keep cells from absorbing too much water. © 2013 Pearson Education, Inc. 27

28 Cell Surfaces Animal cells
lack cell walls and typically have an extracellular matrix, which helps hold cells together in tissues and protects and supports them. The surfaces of most animal cells contain cell junctions, structures that connect cells together into tissues, allowing them to function in a coordinated way. © 2013 Pearson Education, Inc. 28

29 THE NUCLEUS AND RIBOSOMES: GENETIC CONTROL OF THE CELL
The nucleus is the chief executive of the cell (brain of the cell). Genes in the nucleus store information necessary to produce proteins. Proteins do most of the work of the cell. Structure and Function of the Nucleus The nucleus is bordered by a double membrane called the nuclear envelope. Pores in the envelope allow materials to move between the nucleus and cytoplasm. The nucleus also contains a nucleolus where ribosomes are made Its function is to produce ribosomal subunits from rRNA and proteins Pass through nuclear pores into the cytoplasm and combine to form ribosomes 29

30 The nucleus Surface of nuclear envelope Nuclear pores Chromatin fiber
Ribosomes Nucleolus Nuclear pore The nucleus TEM TEM Surface of nuclear envelope Nuclear pores Figure 4.8 Figure 4.8 The nucleus

31 Structure and Function of the Nucleus
Stored in the nucleus are long DNA molecules and associated proteins that form fibers called chromatin. Each long chromatin fiber constitutes one chromosome. The number of chromosomes in a cell depends on the species (Human have 46, Drosophila has 4, some plants have 100). © 2013 Pearson Education, Inc. 31

32 The relationship between DNA, chromatin, and a chromosome
DNA molecule The relationship between DNA, chromatin, and a chromosome Proteins Chromatin fiber Chromosome Figure 4.9 Figure 4.9 The relationship between DNA, chromatin, and a chromosome

33 Ribosomes Ribosomes are responsible for protein synthesis.
Ribosome components are made in the nucleolus but assembled in the cytoplasm. mRNA leave the nucleolus and go to the ribosomes, just like a factory in a little house Ribosome Protein mRNA Computer model of a ribosome synthesizing a protein Figure 4.10 A computer model of a ribosome synthesizing a protein

34 Ribosomes The locations of ribosomes
Ribosomes may assemble proteins while the ribosomes are suspended in the fluid of the cytoplasm -free ribosomes or Function is to synthesize proteins that function within the cytosol attached to the outside of the nucleus or an organelle called the Endoplasmic reticulum – bound ribosomes. Synthesize proteins for export or for membranes TEM The locations of ribosomes Ribosomes in Cytoplasm (free) Ribosomes attached to Endoplasmic reticulum Figure 4.11 Figure 4.11 The locations of ribosomes (TEM) 34

35 How DNA Directs Protein Production
DNA programs protein production in the cytoplasm by transferring its coded information into messenger RNA (mRNA). Messenger RNA exits the nucleus through pores in the nuclear envelope. A ribosome moves along the mRNA, translating the genetic message into a protein with a specific amino acid sequence. © 2013 Pearson Education, Inc. 35

36 1 2 3 DNA Synthesis of mRNA in the nucleus mRNA Nucleus Cytoplasm mRNA
Figure DNA 1 Synthesis of mRNA in the nucleus mRNA Nucleus Cytoplasm 2 mRNA Movement of mRNA into cytoplasm via nuclear pore Ribosome 3 Synthesis of protein in the cytoplasm Protein Figure 4.12 DNA  RNA  Protein (step 3)

37 THE ENDOMEMBRANE SYSTEM: MANUFACTURING AND DISTRIBUTING CELLULAR PRODUCTS
Many membranous organelles forming the endomembrane system in a cell are interconnected either directly by their membranes or by transfer of membrane segments between them. © 2013 Pearson Education, Inc. 37

38 The Endoplasmic Reticulum
The endoplasmic reticulum (ER) is one of the main manufacturing facilities in a cell. The ER Produces an enormous variety of molecules is connected to the nuclear envelope, and Is composed of smooth and rough ER Nuclear envelope Smooth ER Rough ER Ribosomes TEM

39 Rough ER and Smooth ER The “rough” in rough ER refers to ribosomes that stud the outside of this portion of the ER membrane. These ribosomes produce membrane proteins and secretory proteins. Some products manufactured by rough ER are dispatched to other locations in the cell by transport vesicles, sacs made of membrane that bud off from the rough ER. The smooth ER lacks surface ribosomes, produces lipids (phospholipids) , including steroids, and Responsible for hydrolysis of breaking down the glycogen in the liver into glucose helps liver cells detoxify circulating drugs and poisons (alcohol and barbiturates) 39

40 How rough ER manufactures and packages
secretory proteins Proteins are often modified in the ER. Secretory proteins depart in transport vesicles. Vesicles bud off from the ER. A ribosome links amino acids into a polypeptide. Ribosome Transport vesicle Polypeptide Protein Rough ER Figure 4.14 How rough ER manufactures and packages secretory proteins

41 The Golgi Apparatus The Golgi apparatus (Here is where things from the ER end up ) works in partnership with the ER and Function : receives, refines, stores, and distributes chemical products of the cell Center of manufacturing, warehousing, sorting and shipping Structure : flattened membranous sacs Two sides = 2 functions “Cis” Receiving side fuse with vesicles “Trans” Shipping side buds off vesicles that travel to other sites 41

42 “Receiving” side of the Golgi apparatus (Cis-side)
Transport vesicle from rough ER “Receiving” side of the Golgi apparatus 1 New vesicle forming 2 Transport vesicle from the Golgi apparatus 3 Colorized SEM “Shipping” side of the Golgi apparatus Plasma membrane New vesicle forming (trans side ) Figure 4.15 Figure 4.15 The Golgi apparatus

43 Lysosomes There are other kinds of vesicles and lysosomes are one of them A lysosome is a membrane-bound sac of digestive enzymes found in animal cells. Lysosomes are absent from most plant cells. Enzymes in a lysosome can break down large molecules such as proteins, polysaccharides, fats, and nucleic acids. © 2013 Pearson Education, Inc. 43

44 Animation: Lysosome Formation
Lysosomes Lysosomes have several types of digestive functions. Many cells engulf nutrients in tiny cytoplasmic sacs called food vacuoles. These food vacuoles fuse with lysosomes, exposing food to enzymes to digest the food. Small molecules from digestion leave the lysosome and nourish the cell. Lysosomes can also Destroy harmful bacteria Break down damaged organelles sculpt tissues during embryonic development, helping to form structures such as fingers. Animation: Lysosome Formation 44

45 A lysosome digesting food Lysosome and food vacuole fuse together
Plasma membrane Digestive enzymes Lysosome Lysosome Digestion Digestion Food vacuole Vesicle containing damaged organelle A lysosome digesting food Lysosome and food vacuole fuse together (b) A lysosome breaking down the molecules of damaged organelles Organelle fragment Vesicle containing two damaged organelles Organelle fragment TEM Figure 4.16 Figure 4.16 Two functions of lysosomes

46 Vacuoles Vacuoles are membranous sacs that bud from the
Endoplasmic recticulum Golgi Plasma membrane Contractile vacuoles of protists pump out excess water in the cell. Central vacuoles of plants Store nutrients Absorb water May contain pigments or poisons Video: Cytoplasmic Streaming Video: Chlamydomonas Video: Paramecium Vacuole Blast Animation: Vacuole

47 Two types of vacuoles (a) Contractile vacuole in Paramecium
A vacuole filling with water LM A vacuole contracting LM (a) Contractile vacuole in Paramecium Two types of vacuoles Colorized TEM Central vacuole (b) Central vacuole in a plant cell Figure 4.17 Figure 4.17 Two types of vacuoles

48 Blast Animation : Vesicle Transport Along Microtubules
Vacuoles To review, the endomembrane system interconnects the nuclear envelope, ER, Golgi, lysosomes, vacuoles, and plasma membrane. Blast Animation : Vesicle Transport Along Microtubules © 2013 Pearson Education, Inc. 48

49 Transport vesicles carry enzymes and
Figure 4.18 Rough ER Golgi apparatus Transport vesicle Transport vesicles carry enzymes and other proteins from the rough ER to the Golgi for processing. Plasma membrane Lysosomes carrying digestive enzymes can fuse with other vesicles. Golgi apparatus Secretory protein TEM Some products are secreted from the cell. Vacuoles store some cell products. New vesicle forming Transport vesicle from the Golgi apparatus Plasma membrane Figure 4.18 Review of the endomembrane system

50 CHLOROPLASTS AND MITOCHONDRIA: ENERGY CONVERSION
All the work that these organelles are doing require energy Cells require a continuous energy supply to perform the work of life. Two organelles act as cellular power stations: chloroplasts and mitochondria. Plants have both Most of the living world runs on the energy provided by photosynthesis. Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar and other organic molecules. 50

51 Chloroplasts Chloroplasts are
unique to the photosynthetic cells of plants and algae and the organelles that perform photosynthesis. Chloroplasts are divided into three major compartments by internal membranes: the space between the two membranes, the stroma, a thick fluid within the chloroplast, and the space within grana, membrane-enclosed discs and tubes that trap light energy and convert it to chemical energy. © 2013 Pearson Education, Inc. 51

52 Stroma (fluid in chloroplast)
Figure 4.19 Inner and outer membranes Space between membranes Granum Stroma (fluid in chloroplast) TEM Figure 4.19 The chloroplast: site of photosynthesis

53 Mitochondria Mitochondria
are the organelles of cellular respiration (in the presence of O2), are found in almost all eukaryotic cells, and produce ATP from the energy of food molecules. An envelope of two membranes encloses the mitochondrion: an outer smooth membrane and an inner membrane that has numerous infoldings called cristae and encloses a thick fluid called the matrix (where certain chemical reactions occur in the breaking of sugar ). 53

54 The mitochondrion: site of cellular respiration
Outer membrane TEM Inner membrane Cristae Matrix Space between membranes Figure 4.20 Figure 4.20 The mitochondrion: site of cellular respiration

55 Mitochondria Mitochondria and chloroplasts contain their own DNA, which encodes some of their proteins. This DNA is evidence that mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past. © 2013 Pearson Education, Inc. 55

56 Intermediate filaments and microfilaments are thinner and solid.
THE CYTOSKELETON: (Linking every thing together ) CELL SHAPE AND MOVEMENT The cytoskeleton is a network of fibers extending throughout the cytoplasm. Provides mechanical support to the cell and maintains its shape The cytoskeleton contains several types of fibers made from different proteins: Microtubules Are straight and hollow Guide the movement of organelles and chromosomes Intermediate filaments and microfilaments are thinner and solid. The cytoskeleton provides anchorage and reinforcement for many organelles. 56

57 Maintaining Cell Shape
The cytoskeleton is quite dynamic. Changes in the cytoskeleton contribute to the amoeboid (crawling) movements of the protist Amoeba and some of our white blood cells. © 2013 Pearson Education, Inc. 57

58 (a) Microtubules in the cytoskeleton
(b) Microtubules and movement LM (a) Microtubules in the cytoskeleton LM Figure 4.21 Figure 4.21 The cytoskeleton

59 Cilia and Flagella are also made of microtubules
Cilia and flagella are motile appendages that aid in movement. Flagella propel the cell through their undulating, whiplike motion. Cilia move in a coordinated back-and-forth motion. Cilia and flagella have the same basic architecture, but cilia are generally shorter and more numerous than flagella. © 2013 Pearson Education, Inc. 59

60 Animation: Cilia and Flagella Video: Paramecium Cilia
Cilia may extend from nonmoving cells. On cells lining the human trachea, cilia help sweep mucus with trapped debris out of the lungs. Fallopian tubes are also cover by cilia in femelle Animation: Cilia and Flagella Video: Euglena Video: Paramecium Cilia © 2013 Pearson Education, Inc.

61 Examples of flagella and cilia
Colorized SEM Colorized SEM (a) Flagellum of a human sperm cell (b) Cilia on a protist (c) Cilia lining the respiratory tract Colorized SEM Figure 4.22 Figure 4.22 Examples of flagella and cilia

62 Organelle Function Structure
Cell membrane Selective barrier Cytoplasm Nucleus Contain the genetic material Nuclear envelop, Nucleolus, Chromatin Nucleolus Produce ribosomal subunit from rRNA Ribosomes Protein synthesis Composed of two subunits Endoplasmic Reticulum Manufacture proteins - Membrane connected to the nuclear envelope and extends throughout cell Golgi apparatus receives, refines, stores, and distributes cell products - Flattened membranous sacs - Two sides (receiving and shipping) with two different functions Lysosomes Function as a little stomach of the cell - Membrane-bounded sac of hydrolytic enzymes Mitochondria Generate ATP from breaking down sugars, fats, and others -two membranes; Matrix; DNA; Ribosomes; Enzymes Cytoskeleton Support and movement

63 Evolution Connection: The Evolution of Antibiotic Resistance
Many antibiotics disrupt cellular structures of invading microorganisms. Introduced in the 1940s, penicillin worked well against such infections. But over time, bacteria that were resistant to antibiotics, such as the MRSA strain, were favored. The widespread use and abuse of antibiotics continue to favor bacteria that resist antibiotics. © 2013 Pearson Education, Inc. 63

64 Figure 4.23 Figure 4.23 The changing role of antibiotics

65 Who am I? Who am I?

66 Who am I?

67 CATEGORIES OF CELLS Prokaryotic Cells Eukaryotic Cells • Smaller
Figure 4.UN11 CATEGORIES OF CELLS Prokaryotic Cells Eukaryotic Cells • Smaller • Simpler • Most do not have organelles • Found in bacteria and archaea • Larger • More complex • Have organelles • Found in protists, plants, fungi, animals Figure 4.UN11 Summary of Key Concepts: The Two Major Categories of Cells

68 Cytoplasm (inside of cell)
Figure 4.UN12 Outside of cell Phospholipid Hydrophilic Protein Hydrophobic Hydrophilic Cytoplasm (inside of cell) Figure 4.UN12 Summary of Key Concepts: The Plasma Membrane: A Fluid Mosaic of Lipids and Proteins

69 Chemical energy (food) CELLULAR RESPIRATION
Figure 4.UN13 Mitochondrion Chloroplast Light energy Chemical energy (food) CELLULAR RESPIRATION PHOTOSYNTHESIS ATP Figure 4.UN13 Summary of Key Concepts: Chloroplasts and Mitochondria