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4 A Tour of the Cell.

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1 4 A Tour of the Cell

2 Do now: A cell (cube shape) is 5cm in length. Calculate surface area to volume ratio. Show all work. How are prokaryotic cells different from eukaryotic cells? Categorize the kingdoms into each How are plant cells different from animal cells?

3 Overview: The Fundamental Units of Life
All organisms are made of one or more cells. Smallest unit of life All cells are related by their descent from earlier cells Though cells can differ substantially from one another, they share common features © 2014 Pearson Education, Inc. 3

4 Why are cells small? Metabolic requirements set upper limits on the size of cells The ratio of surface area to volume of a cell is critical As the surface area increases by a factor of n2, the volume increases by a factor of n3 Small cells have a greater surface area relative to volume © 2014 Pearson Education, Inc. 4

5 Surface area increases while total volume remains constant
Figure 4.6 Surface area increases while total volume remains constant 5 1 1 Total surface area [sum of the surface areas (height  width) of all box sides  number of boxes] 6 150 750 Total volume [height  width  length  number of boxes] Figure 4.6 Geometric relationships between surface area and volume 1 125 125 Surface-to-volume ratio [surface area  volume] 6 1.2 6 5

6 Concept 4.1: Biologists use microscopes and the tools of biochemistry to study cells
Most cells are between 1 and 100 m in diameter, too small to be seen by the unaided eye © 2014 Pearson Education, Inc. 6

7 Super- resolution microscopy
Figure 4.2 10 m Human height 1 m Length of some nerve and muscle cells 0.1 m Unaided eye Chicken egg 1 cm Frog egg 1 mm Human egg 100 m Most plant and animal cells LM 10 m Nucleus Most bacteria Mitochondrion 1 m EM Figure 4.2 The size range of cells and how we view them Smallest bacteria 100 nm Super- resolution microscopy Viruses Ribosomes 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms 7

8 Most subcellular structures, including organelles (membrane-enclosed compartments), are too small to be resolved by light microscopy © 2014 Pearson Education, Inc. 8

9 TEM is used mainly to study the internal structure of cells
Two basic types of electron microscopes (EMs) are used to study subcellular structures Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look three-dimensional Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen TEM is used mainly to study the internal structure of cells © 2014 Pearson Education, Inc. 9

10 Electron Microscopy (EM)
Figure 4.3 Light Microscopy (LM) 50 m Brightfield (unstained specimen) Brightfield (stained specimen) Phase-contrast Differential-interference contrast (Nomarski) 50 m 10 m Fluorescence Confocal Electron Microscopy (EM) Longitudinal section of cilium Cross section of cilium Figure 4.3 Exploring microscopy Cilia 2 m Transmission electron microscopy (TEM) Scanning electron microscopy (SEM) 2 m 10

11 Do Now Q#1 categorize kingdoms
Prokaryotic Bacteria Archaea Eukaryotic Protists Fungi animals plants © 2014 Pearson Education, Inc. 11

12 Do Now Q #1: differences between eukaryotic and prokaryotic
DNA in a nucleus that is bounded by a membranous nuclear envelope Membrane-bound organelles (ex: mitochondria, ER) larger No nucleus DNA in an unbound region called the nucleoid No membrane-bound organelles

13 Comparing Prokaryotic and Eukaryotic Cells
Basic features of all cells Plasma membrane Semifluid substance called cytosol/cytoplasm Chromosomes (carry genes- segments of DNA) Ribosomes (make proteins) © 2014 Pearson Education, Inc. 13

14 Is this a prokayotic or eukaryotic cell?
Fimbriae Nucleoid Ribosomes Plasma membrane chromosome Cell wall Capsule 0.5 m Flagella (a) A typical rod-shaped bacterium (b) A thin section through the bacterium Bacillus coagulans (TEM) Figure 4.4 A prokaryotic cell 14

15 Review Of Organelles Organelle : cell :: organ system :: organism
Structure enables function!

16 Cell/Plasma Membrane Structure: Function
The general structure of a biological membrane is a double layer of phospholipids Function selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell © 2014 Pearson Education, Inc. 16

17 A Panoramic View of the Eukaryotic Cell
A eukaryotic cell has internal membranes that divide the cell into compartments—organelles The plasma membrane and organelle membranes participate directly in the cell’s metabolism Animation: Tour of an Animal Cell Animation: Tour of a Plant Cell © 2014 Pearson Education, Inc. 17

18 M1 A M M2 B C M3 D L E E1 E2 K E3 F J G I H Figure 4.7a
Figure 4.7a Exploring eukaryotic cells (part 1: animal cell cutaway) F J G H I 18

19 ENDOPLASMIC RETICULUM (ER) Nuclear envelope Smooth ER NUCLEUS
Figure 4.7a ENDOPLASMIC RETICULUM (ER) Nuclear envelope Smooth ER NUCLEUS Nucleolus Flagellum Rough ER Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Ribosomes Microtubules Figure 4.7a Exploring eukaryotic cells (part 1: animal cell cutaway) Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome 19

20 M A1 A2 L A3 A K J B i1 I i.2 i.3 C D E H F G Figure 4.7b
Figure 4.7b Exploring eukaryotic cells (part 2: plant cell cutaway) C D E H F G 20

21 Rough endoplasmic Nuclear envelope reticulum Nucleolus
Figure 4.7b Rough endoplasmic reticulum Nuclear envelope Nucleolus Smooth endoplasmic reticulum Chromatin NUCLEUS Ribosomes Central vacuole Golgi apparatus Microfilaments Intermediate filaments CYTO- SKELETON Microtubules Figure 4.7b Exploring eukaryotic cells (part 2: plant cell cutaway) Mitochondrion Peroxisome Plasma membrane Chloroplast Cell wall Plasmodesmata Wall of adjacent cell 21

22 Close-up of nuclear envelope Chromatin Nucleus Nucleolus Chromatin
Figure 4.8a Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Pore complex Figure 4.8a The nucleus and its envelope (part 1: detail of art) Ribosome Close-up of nuclear envelope Chromatin 22

23 Nucleus Structure: The nuclear envelope encloses the nucleus, separating it from the cytoplasm The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer Function: The nucleus contains most of the DNA in a eukaryotic cell DNA contains information on how to make proteins © 2014 Pearson Education, Inc. 23

24 Ribosomes: Protein Factories
Structure: Made up of two parts, small Function: Ribosomes carry out protein synthesis In the cytosol (free ribosomes) On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes) © 2014 Pearson Education, Inc. 24

25 Endomembrane System- **important topic on the AP exam**
Components of the endomembrane system Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane These components are either continuous or connected through transfer by vesicles © 2014 Pearson Education, Inc. 25

26 The Endoplasmic Reticulum: Biosynthetic Factory
Structure: The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER Smooth ER: lacks ribosomes Rough ER: surface is studded with ribosomes Video: Endoplasmic Reticulum Video: ER and Mitochondria © 2014 Pearson Education, Inc. 26

27 Functions of Smooth ER The smooth ER Synthesizes lipids
Metabolizes carbohydrates Detoxifies drugs and poisons Stores calcium ions © 2014 Pearson Education, Inc. 27

28 Functions of Rough ER The rough ER
Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles, proteins surrounded by membranes Is a membrane factory for the cell © 2014 Pearson Education, Inc. 28

29 The Golgi Apparatus: Shipping and Receiving Center
Structure: The Golgi apparatus consists of flattened membranous sacs called cisternae Functions Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles Video: ER to Golgi Traffic Video: Golgi 3-D Video: Golgi Secretion © 2014 Pearson Education, Inc. 29

30 Lysosomes: Digestive Compartments
Structure: membranous sac of hydrolytic enzymes Function Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Lysosomal enzymes work best in the acidic environment inside the lysosome Also take part in phagocytosis © 2014 Pearson Education, Inc. 30

31 Vacuoles: Diverse Maintenance Compartments
Vacuoles are large vesicles derived from the endoplasmic reticulum and Golgi apparatus Food vacuoles are formed by phagocytosis Contractile vacuoles, found in many freshwater protists, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water © 2014 Pearson Education, Inc. 31

32 Central vacuole Cytosol Central vacuole Nucleus Cell wall Chloroplast
Figure 4.14 Central vacuole Cytosol Central vacuole Nucleus Figure 4.14 The plant cell vacuole Cell wall Chloroplast Plant cell vacuole 5 m 32

33 The Endomembrane System: A Review
The endomembrane system is a complex and dynamic player in the cell’s compartmental organization © 2014 Pearson Education, Inc. 33

34 Nucleus Rough ER Smooth ER Plasma membrane Figure 4.15-1
Figure Review: relationships among organelles of the endomembrane system (step 1) Plasma membrane 34

35 Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi
Figure Nucleus Rough ER Smooth ER cis Golgi Figure Review: relationships among organelles of the endomembrane system (step 2) Plasma membrane trans Golgi 35

36 Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi
Figure Nucleus Rough ER Smooth ER cis Golgi Figure Review: relationships among organelles of the endomembrane system (step 3) Plasma membrane trans Golgi 36

37 Mitochondria and chloroplasts change energy from one form to another
Mitochondria are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP Chloroplasts, found in plants and algae, are the sites of photosynthesis Peroxisomes are oxidative organelles © 2014 Pearson Education, Inc. 37

38 What kind of cell is this?
Figure 4.16 ___________ ________ What is happening here? ______ What kind of cell Is this? ____________ What is happening here? At least one cell Figure 4.16 The endosymbiont theory of the origin of mitochondria and chloroplasts in eukaryotic cells _______ What kind of cell is This? _____________ What kind of cell is this? 38

39 using nonphotosynthetic prokaryote, which becomes a mitochondrion
Figure 4.16 Endoplasmic reticulum Nucleus Engulfing of oxygen- using nonphotosynthetic prokaryote, which becomes a mitochondrion Nuclear envelope Ancestor of eukaryotic cells (host cell) Mitochondrion Engulfing of photosynthetic prokaryote At least one cell Figure 4.16 The endosymbiont theory of the origin of mitochondria and chloroplasts in eukaryotic cells Chloroplast Nonphotosynthetic eukaryote Mitochondrion Photosynthetic eukaryote 39

40 The endosymbiont theory
An early ancestor of eukaryotic cells engulfed a nonphotosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host The host cell and endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion At least one of these cells may have taken up a photosynthetic prokaryote, becoming the ancestor of cells that contain chloroplasts Video: ER and Mitochondria Video: Mitochondria 3-D © 2014 Pearson Education, Inc. 40

41 The Evolutionary Origins of Mitochondria and Chloroplasts
Mitochondria and chloroplasts have similarities with bacteria Enveloped by a double membrane Contain free ribosomes and circular DNA molecules Grow and reproduce somewhat independently in cells © 2014 Pearson Education, Inc. 41

42 Outer membrane Inner membrane
Figure 4.17 Mitochondrion Intermembrane space Outer membrane DNA Inner membrane Free ribosomes in the mitochondrial matrix Figure 4.17 The mitochondrion, site of cellular respiration Cristae Matrix 0.1 m 42

43 Mitochondria: Chemical Energy Conversion
Structure: They have a smooth outer membrane and an inner membrane folded into cristae The inner membrane creates two compartments: intermembrane space and mitochondrial matrix Function: Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesize ATP © 2014 Pearson Education, Inc. 43

44 Inner and outer membranes
Figure 4.18a Ribosomes Stroma Inner and outer membranes Granum DNA Figure 4.18a The chloroplast, site of photosynthesis (part 1: detail) Thylakoid Intermembrane space 1 m (a) Diagram and TEM of chloroplast 44

45 Chloroplasts: Capture of Light Energy
Structure: Chloroplast includes Thylakoids, membranous sacs, stacked to form a granum Stroma, the internal fluid Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae © 2014 Pearson Education, Inc. 45

46 Peroxisomes: Oxidation
Structure: Peroxisomes are specialized metabolic compartments bounded by a single membrane Function: Peroxisomes produce hydrogen peroxide and convert it to water Video: Cytoskeleton in Neuron © 2014 Pearson Education, Inc. 46

47 Cytoskeleton Structure: Function:
The cytoskeleton is a network of fibers extending throughout the cytoplasm Function: It organizes the cell’s structures and activities, anchoring many organelles Video: Microtubule Transport Video: Organelle Movement Video: Organelle Transport © 2014 Pearson Education, Inc. 47

48 Components of the Cytoskeleton
Three main types of fibers make up the cytoskeleton Microtubules are the thickest of the three components of the cytoskeleton Microfilaments, also called actin filaments, are the thinnest components Intermediate filaments are fibers with diameters in a middle range © 2014 Pearson Education, Inc. 48

49 Table 4.1 Table 4.1 The structure and function of the cytoskeleton 49

50 Centrosome Microtubule Centrioles Figure 4.22
Figure 4.22 Centrosome containing a pair of centrioles Centrioles 50

51 Cilia and Flagella Microtubules control the beating of cilia and flagella, microtubule-containing extensions projecting from some cells How are flagella and cilia different? Flagella are limited to one or a few per cell, while cilia occur in large numbers on cell surfaces © 2014 Pearson Education, Inc. 51

52 Microfilaments (Actin Filaments)
Microfilaments are thin solid rods, built from molecules of globular actin subunits Function: Muscle: The structural role of microfilaments is to bear tension, resisting pulling forces within the cell Bundles of microfilaments make up the core of microvilli of intestinal cells © 2014 Pearson Education, Inc. 52

53 Intermediate Filaments
Intermediate filaments are larger than microfilaments but smaller than microtubules They support cell shape and fix organelles in place Intermediate filaments are more permanent cytoskeleton elements than the other two classes © 2014 Pearson Education, Inc. 53

54 Concept 4.7: Extracellular components and connections between cells help coordinate cellular activities Most cells synthesize and secrete materials that are external to the plasma membrane These extracellular materials are involved in many cellular functions © 2014 Pearson Education, Inc. 54

55 Cell Walls of Plants The cell wall is an extracellular structure that distinguishes plant cells from animal cells Prokaryotes, fungi, and some protists also have cell walls Structure: Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein Function: The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water © 2014 Pearson Education, Inc. 55

56 Plasmodesmata are channels between adjacent plant cells
Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell Video: Collagen Model Video: Extracellular Matrix Video: Fibronectin © 2014 Pearson Education, Inc. 56

57 Figure 4.26a Figure 4.26a Extracellular matrix (ECM) of an animal cell (part 1: detail of art) 57

58 The Extracellular Matrix (ECM) of Animal Cells
Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM) The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin ECM proteins bind to receptor proteins in the plasma membrane called integrins © 2014 Pearson Education, Inc. 58

59 Cell Junctions Neighboring cells in an animal or plant often adhere, interact, and communicate through direct physical contact There are several types of intercellular junctions that facilitate this Plasmodesmata Tight junctions Desmosomes Gap junctions © 2014 Pearson Education, Inc. 59

60 Tight junctions prevent fluid from moving across a layer of cells
Figure 4.27 Tight junctions prevent fluid from moving across a layer of cells Tight junction TEM 0.5 m Tight junction Intermediate filaments Desmosome TEM 1 m Figure 4.27 Exploring cell junctions in animal tissues Gap junction Ions or small molecules Space between cells TEM Extracellular matrix Plasma membranes of adjacent cells 0.1 m 60

61 Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells
Animal cells have three main types of cell junctions Tight junctions Desmosomes Gap junctions All are especially common in epithelial tissue Animation: Desmosomes Animation: Gap Junctions Animation: Tight Junctions © 2014 Pearson Education, Inc. 61

62 Do now: Compare the following organelles to an organ system and justify your comparison: Mitochondria Lysosome Nucleus ER/Golgi

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