Cells. Stef Elorriaga 4/4/2016 BIO102

Transcription

1 Cells Stef Elorriaga 4/4/2016 BIO102 1

2 The domains and kingdoms of life Three domains Bacteria Archaea Eukarya Six kingdoms Bacteria Archaea Protista Plantae Fungi Animalia 2

3 What is a cell? A cell is the main unit of life 3

4 How can we study cells? Microscopes! 4

5 Types of microscopes Light Simple Compound Electron Scanning electron microscope (SEM) Transmission electron microscope (TEM) 5

6 What is cell theory? The cell theory states that cells are the basic units of life Proposed by botanist Matthias Schleiden and zoologist Theodor Schwann in

7 What is cell theory? Three principles comprise the cell theory 1. Every living organism is made of one or more cells 7

8 What is cell theory? Three principles comprise the cell theory 2. The smallest organisms are single cells, and cells are the functional units of multicellular organisms 8

9 What is cell theory? Three principles comprise the cell theory 3. All cells arise from preexisting cells 9

10 Main two types of cells Main two types of cells: Prokaryotic (meaning before nucleus ) cells Eukaryotic (meaning true nucleus ) cells nucleus cytoplasm lysosome chromosome (DNA) ribosomes plasmid (DNA) cytoplasm cell wall plasma membrane cell wall cytoplasmic fluid plasma membrane free ribosome 10

11 Prokaryotes Unicellular All cells identical no specialized function Lack nucleus, other membrane-bound organelles Possess specialized surface features and fewer specialized structures within their cytoplasm 11

12 Prokaryotic cells Most have a stiff cell wall (peptidoglycan wall) Prokaryotic cells can take several shapes Rod-shaped bacilli Spiral-shaped spirilla Spherical cocci 12

13 Prokaryotic cells Prokaryotic cells have no nuclear membrane or membrane-bound organelles present In the central region of the cell is an area called the nucleoid Within the nucleoid is a single, circular chromosome of DNA Small rings of DNA (plasmids) are located in the cytoplasm 13

14 Prokaryotic cells Some bacteria have pili (meaning hairs) Attachment pili or fimbriae are short and abundant; they help bacteria adhere to structures Sex pili are few in number and long Some bacteria have a flagellum Locomotion 14

15 Eukaryotes May be unicellular Examples: yeast, amoebas 15

16 Eukaryotes May be multicellular Examples: plants, animals 16

17 Eukaryotic Cells Differ greatly in appearance and function Four basic components in common 1. Plasma membrane Isolation Protection Sensitivity Support Gatekeeper 17

18 Eukaryotic Cells Differ greatly in appearance and function Four basic components in common 2. Cytoplasm Material inside the cell but outside the nucleus Contains the cytosol and organelles 18

19 Eukaryotic Cells Differ greatly in appearance and function Four basic components in common 3. The nucleus Control center the brain of the cell Contains the DNA 19

20 Eukaryotic Cells Differ greatly in appearance and function Four basic components in common 4. Organelles Organs of the cell Perform specific functions Some bound by membranes 20

21 Cytoplasm Everything inside the membrane, except the nucleus A LOT more on the membrane later Includes Cytosol = liquid portion Organelles 21

22 Organelles Non-membranous Cell wall Cytoskeleton Cellular extensions Microvilli Cilia Flagella Ribosomes Membranous Endomembrane system Vacuoles Double Membrane Nucleus Mitochondria Plastids Chloroplasts 22

23 Cell membrane All cells are surrounded by a cell membrane Also called a plasma membrane Consists of a bilayer made of mostly phospholipids Critical to cell function Discussed in great detail later 23

24 Cell Wall Plants, fungi, and bacteria are also have cell walls Animal cells do not All have a cell membrane Cell membrane 24

25 Cell wall Made of polysaccharides secreted through plasma membrane Non-living Exterior to cell Cell walls of adjacent plant cells stuck together with pectin 25

26 Cell wall Porous Oxygen, carbon dioxide, water carrying small molecules flow through freely 26

27 Cell wall Adds strength and integrity to cells Plants, fungi don t have bones Allows them to withstand gravity and wind and grow upright 27

28 Cytoskeleton Internal protein network of cells Stabilize cell s 3D shape Guide vesicles microtubules (red) intermediate filaments microtubules nucleus microfilaments microfilaments (blue) Cytoskeleton Light micrograph showing the cytoskeleton 28

29 Cytoskeleton The cytoskeleton is composed of three types of protein fibers Thin microfilaments Medium-sized intermediate filaments Thick microtubules microtubules (red) intermediate filaments microtubules nucleus microfilaments microfilaments (blue) Cytoskeleton Light micrograph showing the cytoskeleton 29

30 Cytoskeleton The cytoskeleton regulates the following cell properties: Cell shape Cell movement Organelle movement Cell division intermediate filaments microtubules microfilaments Cytoskeleton 30

31 Cellular extensions Cilia and flagella Hair-like structures that propel cells through fluids or move fluids past cells Arise from a basal body, which anchors them to the plasma membrane Basal bodies are derived from centrioles, which are identical in structure to basal bodies 31

32 protein sidearms central pair of microtubules fused microtubule pair section of cilium 0.1 micrometer Paramecium cilium plasma membrane basal body (extends into cytoplasm) 32

33 Cellular extensions - Cilia Example: trachea, Fallopian tubes propulsion of fluid cilia lining trachea mucus-secreting cells Cilium power stroke plasma membrane return stroke 33

34 Cellular extensions - Flagella Substantially longer than cilia Only example in human body: sperm direction of locomotion propulsion of fluid flagellum of human sperm Flagellum continuous propulsion 34

35 Cellular extensions - microvilli Very small, highly numerous finger-like projections Increase absorptive surface area Example: small intestine 35

36 Ribosomes Site of protein synthesis Abundant in cells that produce a lot of protein Example: human liver cells have on average 13 million ribosomes in each cell! 36

37 Ribosomes Made from rrna (2 units) and proteins Polypeptide chain constructed using information provided by mrna 37

38 Ribosomes Many ribosomes can read the same strand of mrna at once - Polyribosome 38

39 mrna Contains information for: 1. Amino acid sequence 2. Final destination of protein 39

40 mrna Final destination of protein bound for cytosol = binds to free ribosome 40

41 mrna Final destination of protein somewhere else = mrna/ribosome complex associates with endomembrane system 41

42 Endomembrane System Elaborate system of membranes used to make and move proteins in a cell Organelles Used Rough ER Vesicles Golgi apparatus Cell membrane Lysosome Final Destination of Protein Outside cell Within cell membrane Lysosome 42

43 Endoplasmic Reticulum Collection of membranous tubes and envelopes Two forms Smooth endoplasmic reticulum (ser) Site of lipid synthesis, detoxification, calcium storage Abundant in liver, kidney, endocrine glands 43

44 Rough Endoplasmic Reticulum Gateway to endomembrane system Studded with ribosomes Proteins made by ribosomes enter rer through pore Portion of rer pinches off to encapsulate protein in a transport vesicle 44

45 Movement of vesicles Vesicles are membranous sacs transporting molecules to the various regions of the membrane system Exocytosis 1. Vesicles fuse with the plasma membrane 2. Export their contents outside the cell Endocytosis 1. Plasma membrane extends 2. Surrounds material outside the cell 3. Fuses and pinches off to form a vesicle inside the cell 45

46 Exocytosis Some vesicles stay in cytoplasm Others migrate to the Golgi apparatus 46

47 Protein-carrying vesicles from the ER merge with the Golgi apparatus Golgi apparatus Vesicles carrying modified protein leave the Golgi apparatus 47

48 Golgi apparatus Proteins are modified and/or combined in the Golgi, encapsulated and transported to 1. Secretory vesicles Proteins for discharge from cell Examples: insulin, antibodies 48

49 (interstitial fluid) Vesicles merge with the plasma membrane and release antibodies into the interstitial fluid (cytosol) vesicles Completed glycoprotein antibodies are packaged into vesicles on the opposite side of the Golgi apparatus Golgi apparatus Vesicles fuse with the Golgi apparatus, and carbohydrates are added as the protein passes through the compartments The protein is packaged into vesicles and travels to the Golgi apparatus forming vesicle Antibody protein is synthesized on ribosomes and is transported into channels of the rough ER 49

50 Golgi apparatus Proteins are modified and/or combined in the Golgi, encapsulated and transported to 2. Cell membrane components Example: glycoproteins 50

51 Golgi apparatus Proteins are modified and/or combined in the Golgi, encapsulated and transported to 3. Lysosomes Cytosolically-active vesicles 51

52 Lysosomes Contain more than 50 enzymes ph of ~4.5 Break down almost any biomolecule Cell s garbage disposal Can fuse with other membrane-defined structures and release contents Fuses with a food vacuole and digests food into basic nutrients 52

53 (interstitial fluid) food (cytosol) food vacuoles A lysosome fuses with a food vacuole, and the enzymes digest the food lysosome The enzymes are delivered to the lysosome in vesicles The Golgi apparatus modifies the enzymes for export to the lysosomes Golgi apparatus digestive enzymes The enzymes are packaged into vesicles and travel to the Golgi apparatus Digestive enzymes are synthesized on ribosomes and travel through the rough ER 53

54 Vacuoles Membranous, fluid-filled sacks Most cells contain one or more Animal cells have small ones Plant cells typically have one large, central one (may have other, small ones as well) Animal Cell Plant Cell 54

55 Vacuoles Play a role in maintaining cell integrity Regulate cell s water content Example: Paramecia have contractile vacuoles that expel water that leaks in through cell membrane 55

56 Vacuoles Example: Plant s central vacuole fills with water to generate turgor pressure 56

57 Vacuoles Storage site in plants Waste that can t be excreted Poisonous compounds Amino acids, sugars Pigment (flowers) 57

58 Mitochondria Site of ATP synthesis powerhouse of cell Double membrane (inner and outer) Outer membrane is smooth Inner membrane has deep folds called cristae outer membrane inner membrane intermembrane space matrix cristae 0.1 micrometer 58

59 Mitochondria Carry own DNA Make some of their own proteins (contain ribosomes) Only cellular site to use molecular oxygen outer membrane inner membrane intermembrane space matrix cristae 0.1 micrometer 59

60 Mitochondria Provide energy = most abundant in cells that need a lot of energy Compare: sperm vs cartilage 60

61 Plastids Contained ONLY by plants and photosynthetic protists Primarily used for storage Pigments (fruit) Starch 61

62 Chloroplasts Highly specialized plastid Site of photosynthesis Contains Stroma (fluid) Thylakoids (membranous sacks) A stack is called a granum 62

63 Chloroplasts Thylakoids contain a pigment called chlorophyll Gives plants green color Captures energy from sunlight 63

64 Nucleus Control center of cell Surrounded by nuclear envelope Double membrane Covered with pores Water/ions pass through freely Ribosomes stud outer membrane Continuous with endomembrane system 64

65 Nucleus Contains chromatin Unwound protein-chromosome complexes DNA and associated proteins Contains all instructions for building cell s proteins 65

66 Nucleus mrna made in nucleus Exits through nuclear pores Finds ribosomes Translated into protein in the cytoplasm 66

67 Nucleus Contains nucleolus Site of ribosome synthesis 67

68 Connections between cells A tight junction is a watertight seal between two adjacent animal cells Plasmodesmata: channels that pass between cell walls of adjacent plant cells Gap junctions (animal cells) 68