10 m

Human height 1 m Length of some nerve and muscle cells 0.1 m Chicken egg

1 cm Unaided eye

Frog egg 1 mm

100 µm

Most plant and animal cells 10 µm Nucleus Most bacteria Light microscope microscope Light 1 µm Mitochondrion

100 nm Smallest bacteria Viruses

Ribosomes 10 nm Proteins microscope Electron Lipids 1 nm Small molecules

0.1 nm Atoms 1

Fimbriae

Nucleoid

Ribosomes

Plasma membrane

Bacterial Cell wall chromosome Capsule 0.5 µm Flagella (a) A typical (b) A thin section rod-shaped through the bacterium bacterium Bacillus coagulans (TEM)

2 (a) TEM of a plasma Outside of cell membrane

Inside of 0.1 µm cell Carbohydrate side chain

Hydrophilic region

Hydrophobic region Hydrophilic Phospholipid Proteins region (b) Structure of the plasma membrane 3

Surface area increases while total volume remains constant

5 1 1

Total surface area [Sum of the surface areas 6 150 750 (height × width) of all boxes sides × number of boxes]

Total volume [height × width × length × 1 125 125 number of boxes]

Surface-to-volume (S-to-V) ratio 6 1.2 6 [surface area ÷ volume]

4 Nuclear envelope ENDOPLASMIC RETICULUM (ER) Nucleolus NUCLEUS Rough ER Smooth ER Flagellum Chromatin

Centrosome Plasma membrane

CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes

Microvilli

Golgi Peroxisome apparatus

Mitochondrion Lysosome 5

Nuclear envelope Rough endoplasmic reticulum NUCLEUS Nucleolus Chromatin Smooth endoplasmic reticulum Ribosomes

Central vacuole Golgi apparatus Microfilaments Intermediate CYTO- filaments SKELETON Microtubules

Mitochondrion Peroxisome Chloroplast Plasma membrane

Cell wall Plasmodesmata Wall of adjacent cell

6 Nucleus 1 µm Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane

Nuclear pore

Pore complex

Rough ER Surface of nuclear envelope Ribosome 1 µm

0.25 µm

Close-up of nuclear envelope

Pore complexes (TEM) Nuclear lamina (TEM) 7

Cytosol Endoplasmic reticulum (ER)

Free ribosomes

Bound ribosomes

Large subunit

Small 0.5 µm subunit TEM showing ER and ribosomes Diagram of a ribosome

8 Smooth ER

Rough ER Nuclear envelope

ER lumen Cisternae Ribosomes Transitional ER Transport vesicle 200 nm Smooth ER Rough ER

9

cis face (“receiving” side of 0.1 µm Golgi apparatus) Cisternae

trans face (“shipping” side of TEM of Golgi apparatus Golgi apparatus)

10 Nucleus 1 µm Vesicle containing 1 µm two damaged organelles

Mitochondrion fragment

Peroxisome fragment Lysosome Digestive enzymes Lysosome Lysosome

Plasma Peroxisome membrane Digestion

Food vacuole Mitochondrion Digestion Vesicle

(a) Phagocytosis (b) Autophagy

11

Central vacuole

Cytosol

Nucleus Central vacuole

Cell wall

Chloroplast

5 µm 12 Nucleus

Rough ER

Smooth ER cis Golgi

Plasma membrane trans Golgi

13

Intermembrane space Outer membrane

Free ribosomes in the mitochondrial matrix Inner membrane Cristae Matrix

0.1 µm

14 Ribosomes Stroma Inner and outer membranes

Granum

1 µm Thylakoid

15

Chloroplast Peroxisome Mitochondrion

1 µm 16 Microtubule

Microfilaments 0.25 µm

17

Vesicle ATP Receptor for motor protein

Motor protein Microtubule (ATP powered) of cytoskeleton (a)

Microtubule Vesicles 0.25 µm

(b) 18 10 µm 10 µm 10 µm

Column of tubulin dimers Keratin proteins Actin subunit Fibrous subunit (keratins 25 nm coiled together)

7 nm 8–12 nm α β Tubulin dimer 19

Centrosome

Microtubule

Centrioles 0.25 µm

Longitudinal section Microtubules Cross section of one centriole of the other centriole 20 Direction of swimming

(a) Motion of flagella 5 µm

Direction of organism’s movement

Power stroke Recovery stroke

(b) Motion of cilia 15 µm 21

Outer microtubule Plasma 0.1 µm doublet membrane Dynein proteins Central microtubule Radial spoke Protein cross- Microtubules linking outer doublets (b) Cross section of Plasma cilium membrane Basal body

0.5 µm (a) Longitudinal 0.1 µm section of cilium Triplet

(c) Cross section of basal body 22 Microtubule doublets ATP

Dynein protein (a) Effect of unrestrained dynein movement

ATP Cross-linking proteins inside outer doublets

Anchorage in cell

(b) Effect of cross-linking proteins

1 3

2

(c) Wavelike motion 23

Microvillus

Plasma membrane

Microfilaments (actin filaments)

Intermediate filaments

0.25 µm 24 Muscle cell

Actin filament

Myosin filament Myosin arm

(a) Myosin motors in muscle cell contraction

Cortex (outer cytoplasm): gel with actin network

Inner cytoplasm: sol with actin subunits Extending pseudopodium

(b) Amoeboid movement

Nonmoving cortical cytoplasm (gel) Chloroplast

Streaming cytoplasm (sol) Vacuole

Parallel actin filaments Cell wall

(c) Cytoplasmic streaming in plant cells 25

Secondary cell wall Primary cell wall

Middle lamella

1 µm Central vacuole Cytosol Plasma membrane

Plant cell walls

Plasmodesmata 26 Collagen Proteoglycan Polysaccharide EXTRACELLULAR FLUID complex molecule

Carbo- hydrates

Fibronectin Core protein

Integrins

Proteoglycan molecule Plasma membrane Proteoglycan complex

Micro- CYTOPLASM filaments

27

Cell walls

Interior of cell

Interior of cell

0.5 µm Plasmodesmata Plasma membranes

28 Tight junction Tight junctions prevent fluid from moving across a layer of cells

0.5 µm

Tight junction

Intermediate filaments Desmosome

Desmosome Gap 1 µm junctions

Extracellular Space matrix between Gap junction cells Plasma membranes of adjacent cells 0.1 µm 29

Cell Component Structure Function

Concept 6.3 Nucleus Surrounded by nuclear Houses chromosomes, made of The eukaryotic cell’s genetic envelope (double membrane) chromatin (DNA, the genetic instructions are housed in perforated by nuclear pores. material, and proteins); contains the nucleus and carried out The nuclear envelope is nucleoli, where ribosomal by the ribosomes continuous with the subunits are made. Pores endoplasmic reticulum (ER). regulate entry and exit of materials.

(ER)

Ribosome Two subunits made of ribo- Protein synthesis somal RNA and proteins; can be free in cytosol or bound to ER

Concept 6.4 Endoplasmic reticulum Extensive network of Smooth ER: synthesis of The endomembrane system membrane-bound tubules and lipids, metabolism of carbohy- (Nuclear regulates protein traffic and sacs; membrane separates drates, Ca2+ storage, detoxifica- performs metabolic functions envelope) lumen from cytosol; tion of drugs and poisons in the cell continuous with the nuclear envelope. Rough ER: Aids in synthesis of secretory and other proteins from bound ribosomes; adds carbohydrates to glycoproteins; produces new membrane

Golgi apparatus Stacks of flattened Modification of proteins, carbo- membranous hydrates on proteins, and phos- sacs; has polarity pholipids; synthesis of many (cis and trans polysaccharides; sorting of Golgi faces) products, which are then released in vesicles.

Lysosome Membranous sac of hydrolytic Breakdown of ingested substances, enzymes (in animal cells) cell macromolecules, and damaged organelles for recycling

Vacuole Large membrane-bounded Digestion, storage, waste vesicle in plants disposal, water balance, cell growth, and protection

Concept 6.5 Mitochondrion Bounded by double Cellular respiration Mitochondria and chloro- membrane; plasts change energy from inner membrane has one form to another infoldings (cristae)

Chloroplast Typically two membranes Photosynthesis around fluid stroma, which contains membranous thylakoids stacked into grana (in plants)

Peroxisome Specialized metabolic Contains enzymes that transfer compartment bounded by a hydrogen to water, producing single membrane hydrogen peroxide (H2O2) as a by-product, which is converted to water by other enzymes in the peroxisome

30