biol 101 chp 6: a tour of the cell

A Tour of the Cell

BIOL 101: General Biology I

Chapter 6

Rob Swatski Associate Professor of Biology

HACC – York Campus 1

Cells

All organisms made of cells

Simplest level of life

Structure correlated

with function

Cells descend from

previous cells 2

3

4

Microscopy

Light microscopes

Magnification 1000x

Resolution

Contrast

Staining & labeling

10 m

1 m

0.1 m

1 cm

1 mm

100 m Human egg

Frog egg

Chicken egg

Length of some

nerve and

muscle cells

Human height

Un

aid

ed

eye

5

1 mm

100 m

10 m

1 m

100 nm

10 nm

1 nm

0.1 nm Atoms

Small molecules

Lipids

Proteins

Ribosomes

Viruses

Smallest bacteria

Mitochondrion

Most bacteria

Nucleus

Most plant and

animal cells

Human egg

Lig

ht

mic

rosco

py

Ele

ctr

on

mic

rosco

py

Super-

resolution

microscopy

1 cm

Frog egg

6

(a) Brightfield (unstained)

(b) Brightfield (stained)

TECHNIQUE RESULTS

50 µm

7

(c) Phase-contrast

(d) Differential-interference contrast (Nomarski)

TECHNIQUE RESULTS

8

9

Phase-Contrast

Water Bear with Differential-Interference 10

(e) Fluorescence

TECHNIQUE RESULTS

11

Fluorescence 12

(f) Confocal

TECHNIQUE RESULTS

standard fluorescence

13

14 Confocal

15

Electron Microscopes

Scanning Electron

Microscope (SEM)

Transmission Electron

Microscope (TEM)

Scanning electron microscopy (SEM)

TECHNIQUE RESULTS

Transmission electron microscopy (TEM)

16

17 SEM

18

19

TEM

20

Cell Fractionation

Separate organelles

Correlate cytology with biochemistry

Homogenization

Ultracentrifugation

Differential centrifugation

Homogenization

Homogenate

Differential Centrifugation

Tissue cells

TECHNIQUE

21

1,000 g 10 min

Supernatant

20,000 g 20 min

80,000 g 60 min

150,000 g 3 hr

Pellet rich in nuclei and

cellular debris

Pellet rich in mitochondria

(& chloroplasts in plants)

Pellet rich in “microsomes”

(membrane debris) Pellet rich in ribosomes

22

2 Main Types of Cells

Prokaryotic

(Domains Archaea & Bacteria)

Eukaryotic (Domain Eukarya)

23

24

Basic Features of All Cells

Plasma membrane

Cytosol: semifluid

DNA: Chromosomes

carry genes

Ribosomes

25

Features of Prokaryotic

Cells

No nucleus

DNA in nucleoid

No membrane-bound organelles

Cell wall, plasma membrane, &

cytoplasm

Fig. 6-6

(a) A typical rod-shaped bacterium

Ribosomes

Plasma membrane

Cell wall

Capsule

Flagellae

Bacterial chromosome

Fimbriae

Nucleoid

26

Prokaryotic Cell

27

Features of Eukaryotic Cells

DNA in nucleus

Nuclear envelope with pores

Membrane-bound organelles

Plasma membrane & cytoplasm

Larger size

28

29

30

Head

Polar

Hydrophilic

Glycerol & phosphate

Tails

Nonpolar

Hydrophobic

2 Fatty acids

Phospholipid Structure

Plasma Membrane (Phospholipid bilayer)

31

Structure of the Plasma Membrane

Outside of cell

Inside of cell

Hydrophilic region

Hydrophobic region

Hydrophilic region

Proteins

Carbohydrate side-chain

32

33

Permeable

34

Impermeable

35 Semipermeable (Selectively Permeable)

36

Surface Area-to-Volume

Ratio

SA divided by Volume

Membrane relationship

As SA doubles, volume triples

Small cells have more SA relative to

volume

Surface area increases while total volume remains constant

5

1

1

6 150 750

125 125 1

6 6 1.2

Total surface area [Sum of the surface areas

(height width) of all boxes

sides number of boxes]

Total volume [height width length

number of boxes]

Surface-to-volume

(S-to-V) ratio [surface area ÷ volume]

37

ENDOPLASMIC RETICULUM (ER)

Smooth ER Rough ER Flagellum

Centrosome

CYTOSKELETON:

Microfilaments

Intermediate filaments

Microtubules

Microvilli

Peroxisome

Mitochondrion Lysosome

Golgi apparatus

Ribosomes

Plasma membrane

Nuclear envelope

Nucleolus

Chromatin

NUCLEUS

38

39

NUCLEUS Nuclear envelope

Nucleolus

Chromatin

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

Ribosomes

Central vacuole

Microfilaments

Intermediate filaments

Microtubules

CYTO- SKELETON

Chloroplast

Plasmodesmata

Wall of adjacent cell

Cell wall

Plasma membrane

Peroxisome

Mitochondrion

Golgi apparatus

40

41

Cytoplasm

Cytosol

Water Solutes Macro-

molecules

Cyto-skeleton

Protein filaments

Organelles

Membrane-bound

42

43

Nucleus

Nuclear envelope with

pores

Nuclear lamina: protein

Nuclear pores

Chromatin & chromosomes

Nuclear envelope:

Inner membrane

Outer membrane

Nuclear pore

Surface of nuclear envelope

1 m

44

45

DNA

Chromatin

Non-dividing cells

Unorganized, loose threads of DNA & protein

Chromosomes

Dividing cells Genes

46

47

Chromatin

Chromosomes

Chromosomes & loci 48

49

Nucleolus

Inside nucleus

Made of RNA & protein

Site of ribosomal RNA (rRNA)

synthesis

Makes small and large ribosomal

subunits

Ribosomes

Particles consisting of

rRNA & proteins

Made by nucleolus

Small & large subunits

Site of protein synthesis

50 Free Ribosomes

Free & Bound Ribosomes

51

52

Endomembrane System

Plasma membrane

Nuclear envelope

Endoplasmic Reticulum

(ER)

Golgi appara

tus Lysosomes

Vacuoles &

Vesicles

Performs metabolic functions

Regulates protein traffic

Endoplasmic Reticulum

Tube-like membrane

network

Biosynthetic factory

Rough ER

Smooth ER

53

Smooth ER

Rough ER

Cisternae Ribosomes

Transport vesicle

Transitional ER

Nuclear

envelope

ER lumen

54

55

56

Smooth ER Functions

Synthesizes lipids

Metabolizes carbohydrates

Detoxifies drugs & poisons

Stores calcium ions

57

Rough ER Functions

Contains bound ribosomes that

secrete glycoproteins

Makes membrane

proteins

Distributes transport vesicles

Sends vesicles to Golgi

apparatus

58

Golgi Apparatus

Cisternae: flattened

membrane sacs

Modifies products of the

ER

Makes macromolecules

Sorts & packages materials into

transport vesicles

59

60

cis face

trans face 61

Lysosomes

Membrane-bound vesicles

Cellular “stomachs”

Contain hydrolytic enzymes that break down

macromolecules 62

63

Phagocytosis

Phagosome

64

65

Phagocytosis

66

Autophagy

Peroxisome

67

Peroxisomes

Smaller membrane-bound

vesicles

Contain enzymes that oxidize

organic wastes

Convert hydrogen peroxide

water

Break down variety of

macromolecules

68

69

Peroxisome

70

Vacuoles

Larger membrane-bound organelle

derived from ER & Golgi

Food vacuole: from

phagocytosis

Contractile vacuole: protists

Central vacuole: plants

71 Contractile vacuole

72

Central vacuole

73

74

Mitochondria

Double membrane: outer & inner

Site of Aerobic cellular respiration

Makes ATP

In all Eukarya

75

76

Mitochondria Structure

Smooth outer membrane

Folded inner membrane = cristae

Intermembrane space

Matrix

Intermembrane space

Outer

DNA

Inner membrane

Cristae

Matrix

Free

ribosomes

in the

mitochondrial

matrix 0.1 m

membrane

Mitochondria Structure

77

78

Chloroplasts

In plants & protists

Type of plastid

Site of photosynthesis

Contain chlorophyll

79

80

81

Chloroplast Structure

Smooth outer membrane

Inner membranes =

thylakoids

Grana = stacks of thylakoids

Stroma

Ribosomes Stroma

Inner & outer

membranes

Granum

1 m Intermembrane

space

Thylakoid

DNA

Chloroplast Structure

82

83

Mitochondria &

Chloroplasts Similar to bacteria

Have a double membrane

Proteins are made by free

ribosomes

Have their own circular DNA

molecules

– 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

The Endosymbiont Theory

84

Nucleus Endoplasmic

reticulum

Nuclear

envelope

Ancestor of

eukaryotic cells

(host cell)

Engulfing of oxygen-

using nonphotosynthetic

prokaryote, which

becomes a mitochondrion

Mitochondrion

Nonphotosynthetic

eukaryote

Mitochondrion

Photosynthetic eukaryote

Engulfing of

photosynthetic

prokaryote

Chloroplast

85

86

Cytoskeleton

Functions of the Cytoskeleton

Anchors organelles

& organizes cell

structure

Supports cell &

maintains cell shape

Regulates cell division

& biochemical

activities

Interacts with motor proteins to

move organelles

& cells

87

Cytoskeleton

Microfilaments

Intermediate filaments

Microtubules

88

Microtubules 89

Microtubules

Thick, hollow rods of tubulin

Maintain cell shape

Transport organelles & entire cell

Separate chromosomes during

cell division – form spindle

90

Centrosomes

91

Centrosomes

Contain centrioles

9 + 0 arrangement

of MT’s

MT-organizing

centers

Create mitotic spindle

92

Centrioles

93

Mitotic spindle

94

95

Cilia & Flagella

Both made of MT’s sheathed by plasma

membrane

9 + 2 MT arrangement

Anchored to cell by basal body

Motor protein (dynein) drives

bending movement

Cilia

Many

Short

Sweep materials across cell

Flagella

Fewer

Long

Move entire cell

96

97 Cilia

Flagellae 98

99

Basal body

Cilium or Flagellum

9+2

100

Power stroke Recovery stroke

Cilia

Flagellae

101

102

Dynein “Walking”

Dynein arms grab, move, & release

outer MT’s

Protein cross-links limit sliding

MT doublets curve, bending cilium or

flagellum

ATP

Effect of unrestrained dynein movement

103

ATP

Effect of cross-linking proteins

104

105

106

107

Microfilaments

108

Microfilaments

Thin, solid protein fibers

Twisted double-chain of actin

Bear tension & resist pulling forces

inside cell

Form 3-D network (cortex) under

plasma membrane

Functions of Microfilaments

Support & maintain

cell shape & allow

changes to shape

Cell motility:

amoeboid movement

& cytoplasmic streaming

Muscle contraction

Cell division

109

110

111 Microfilament Cortex

112

Microfilament core in microvilli

113

114 Actin (with myosin motors) in muscle

115

116 Myosin motor (head)

117

Cell motility using actin

100 m

Cortex (outer cytoplasm):

gel with actin network

Inner cytoplasm: sol

with actin subunits

Extending

pseudopodium

Amoeboid movement 118

119

120

Cytoplasmic streaming cortex

sol

Intermediate Filaments

Medium-diameter keratin cables

More permanent

Maintain cell shape

Anchor nucleus & other organelles

121

Intermediate Filaments

122

123

Extracellular Structures

Cell walls in plants

Extracellular matrix of animal

cells

Intercellular junctions

124

125

126

Cell Walls in Plants

Cellulose fibers embedded with

polysaccharides & proteins

Protect & maintain cell shape

Prevent excessive uptake of water

127

Structure of the Plant Cell

Wall

Primary cell wall

Middle lamella

Secondary cell wall

Plasmodesmata

Secondary

cell wall

Primary

cell wall

Middle

lamella

Central vacuole

Cytosol

Plasma membrane

Plant cell walls

Plasmodesmata

1 m

128

129

Extracellular Matrix (ECM)

of Animal Cells

Made of glycoproteins:

Collagen, proteoglycans,

fibronectin

ECM proteins bind to receptor proteins called integrins in plasma membrane

130

collagen proteo-glycan

Fibro-nectin

integrin

131

Functions of the ECM

Adhesion

Regulation

Movement

Support

132

Intercellular Junctions

Tight junctions

Desmosomes

Gap junctions

Plasmodesmata

133 Plasmodesmata

134

Plasmodesmata

Tight junctions prevent

fluid from moving

across a layer of cells

Tight junction

Tight junction

TEM 0.5 m

TEM 1 m

TE

M

0.1 m

Extracellular

matrix Plasma membranes

of adjacent cells

Space

between cells

Ions or small

molecules

Desmosome

Intermediate

filaments

Gap

junction

135

136

Tight Junctions

137 Desmosomes

138

Desmosomes

139

Gap Junctions