A tour of the cell

Cells All organisms are made of cells The cell is the simplest collection of matter that can be alive Cell structure is correlated to cellular function All cells are related by their descent from earlier cells

Eukaryotic Cells – membranes to separate function

What is a cell? Basic features of all cells Plasma membrane Semifluid substance called cytosol Chromosomes (carry genes) Ribosomes (make proteins)

Prokaryotes

Eukaryotic vs prokaryotic No nucleus Nucleoid Membrane-less organelles Eukaryotic Nucleus Nuclear envelope Organelles with membranes

Plasma membrane Cell wall Capsule Flagella Figure 6.5 Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial 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 6.5 A prokaryotic cell.

Eukaryotic Cells Have plasma membranes selective barrier TEM of a plasma membrane Eukaryotic Cells Outside of cell Have plasma membranes selective barrier double layer of phospholipids Inside of cell 0.1 m Carbohydrate side chains Hydrophilic region Hydrophobic region Hydrophilic region Phospholipid Proteins (b) Structure of the plasma membrane

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 Figure 6.7 Geometric relationships between surface area and volume. Total volume [height  width  length  number of boxes] 1 125 125 Surface-to-volume (S-to-V) ratio [surface area  volume] 6 1.2 6

Animal Cell ENDOPLASMIC RETICULUM (ER) Nuclear envelope Rough ER Figure 6.8a Animal Cell ENDOPLASMIC RETICULUM (ER) Nuclear envelope Rough ER Smooth ER Flagellum NUCLEUS Nucleolus Chromatin Centrosome Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Figure 6.8 Exploring: Eukaryotic Cells Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome

Animal Cells Fungal Cells 1 m Parent cell 10 m Cell wall Buds Figure 6.8b Animal Cells Fungal Cells 1 m Parent cell 10 m Cell wall Buds Vacuole Cell 5 m Nucleus Nucleus Nucleolus Mitochondrion Human cells from lining of uterus (colorized TEM) Yeast cells budding (colorized SEM) A single yeast cell (colorized TEM) Figure 6.8 Exploring: Eukaryotic Cells

Rough endoplasmic reticulum Figure 6.8c Nuclear envelope Rough endoplasmic reticulum Plant Cell NUCLEUS Smooth endoplasmic reticulum Nucleolus Chromatin Ribosomes Central vacuole Golgi apparatus Microfilaments Intermediate filaments CYTOSKELETON Microtubules Figure 6.8 Exploring: Eukaryotic Cells Mitochondrion Peroxisome Chloroplast Plasma membrane Cell wall Plasmodesmata Wall of adjacent cell

Plant Cells Protistan Cells Figure 6.8d Chlamydomonas (colorized SEM) Flagella Cell 1 m 5 m 8 m Cell wall Nucleus Chloroplast Nucleolus Mitochondrion Vacuole Nucleus Nucleolus Chloroplast Chlamydomonas (colorized SEM) Cells from duckweed (colorized TEM) Cell wall Chlamydomonas (colorized TEM) Figure 6.8 Exploring: Eukaryotic Cells

The Nucleus

The Nucleus: Home of Genetic Instructions The nucleus contains most of the DNA in a eukaryotic cell Ribosomes use the information from the DNA to make proteins

Nuclear Envelope: Separation of Nucleus and cytoplasm Double membrane of lipid bilayer Surrounds nucleus Tightly controlled

Close-up of nuclear envelope Chromatin Figure 6.9a Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Pore complex Ribosome Figure 6.9 The nucleus and its envelope. Close-up of nuclear envelope Chromatin

Surface of nuclear envelope Figure 6.9b 1 m Nuclear envelope: Inner membrane Outer membrane Nuclear pore Figure 6.9 The nucleus and its envelope. Surface of nuclear envelope

Pore complexes regulate entry and exit of nucleus Pore complexes (TEM) Nuclear lamina are a matrix of proteins that line the interior of the nuclear membrane Provide support to the envelope 1 m Figure 6.9 The nucleus and its envelope. Nuclear lamina (TEM)

Chromatin to chromosomes DNA is organized into discrete units called chromosomes Each chromosome composed of a single DNA molecule associated with proteins The DNA and proteins of chromosomes together called chromatin The nucleolus located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis

Ribosomes Made of ribosomal RNA and protein Carry out protein synthesis in two locations

Endomembrane system

endomembrane regulates protein traffic and performs metabolic functions in the cell continuous or connected via transfer by vesicles Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane

Smooth ER Rough ER Nuclear envelope ER lumen Cisternae Transitional ER Ribosomes Transport vesicle

Collectively account for more than ½ the membrane in a cell ER Collectively account for more than ½ the membrane in a cell Membranous cisternae Lumen = internal space Nuclear Envelope continuous with lumen

200 nm Smooth ER Rough ER

Smooth vs Rough ER Synthesizes lipids Metabolizes carbohydrates Smooth ER Rough ER Synthesizes lipids Metabolizes carbohydrates Detoxifies drugs and poisons Stores calcium ions Has bound ribosomes, which secrete glycoproteins Distributes transport vesicles Is a membrane factory for the cell

Ribosome Protein Lumen Endoplasmic Reticulum

Golgi Apparatus Made of flattened stacks = cisternae 2 distinct “sides” cis and trans Modify molecules as they move through Synthesizes macromolecules

Golgi Apparatus cis face (“receiving” side of Golgi apparatus) 0.1 m Cisternae trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus

Lysosomes Membranous sac of enzymes Used to digest macromolecules Contents and membranes of lysozymes synthesized in ER ER protected by 3D structure

Intracellular digestion Phagocytosis – engulf “food” Lysosomes fuse with food vacuole Create nutrients for cell Autophagy – recycling cell’s own materials Damage organelle tagged Surrounded by membrane Lysosome fuses

Vesicle containing two damaged organelles Nucleus 1 m Mitochondrion fragment Lysosome Peroxisome fragment Digestive enzymes Lysosome Lysosome Peroxisome Plasma membrane Digestion Food vacuole Mitochondrion Digestion Vesicle (a) Phagocytosis (b) Autophagy

Animation: Lysosome Formation Right-click slide / select “Play” © 2011 Pearson Education, Inc.

Vacuole diverse maintenance chambers Central vacuole Membranous vesicle from ER Many functions: food, contractile, storage Function varies based on cell structure Cytosol Central vacuole Nucleus Cell wall Chloroplast 5 m

Nucleus Rough ER Smooth ER Plasma membrane Figure 6.15-1 Figure 6.15 Review: relationships among organelles of the endomembrane system. Plasma membrane

Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi Figure 6.15-2 Nucleus Rough ER Smooth ER cis Golgi Figure 6.15 Review: relationships among organelles of the endomembrane system. Plasma membrane trans Golgi

Nucleus Rough ER Smooth ER cis Golgi Plasma membrane trans Golgi Figure 6.15-3 Nucleus Rough ER Smooth ER cis Golgi Figure 6.15 Review: relationships among organelles of the endomembrane system. Plasma membrane trans Golgi

Mitochondria and chroloplasts

Mitochondria Mitochondria are the sites of cellular respiration Turn O2 into ATP Have own DNA Double membrane Contain free ribosomes Grow independently of rest of cell

Free ribosomes in the mitochondrial matrix membrane Figure 6.17a Intermembrane space Outer membrane DNA Inner Free ribosomes in the mitochondrial matrix membrane Cristae Figure 6.17 The mitochondrion, site of cellular respiration. Matrix 0.1 m (a) Diagram and TEM of mitochondrion

Outer membrane Inner membrane Cristae Matrix 0.1 m Figure 6.17aa Outer membrane Inner membrane Figure 6.17 The mitochondrion, site of cellular respiration. Cristae Matrix 0.1 m

Network of mitochondria in a protist cell (LM) Figure 6.17b 10 m Mitochondria Mitochondrial DNA Figure 6.17 The mitochondrion, site of cellular respiration. Nuclear DNA (b) Network of mitochondria in a protist cell (LM)

Chloroplasts Chloroplasts are the sites of photosynthesis Thylakoids are membranous sacs stacked into granum Contain chlorophyll and other enzymes necessary for photosynthesis

(a) Diagram and TEM of chloroplast Figure 6.18a Ribosomes Stroma Inner and outer membranes Granum DNA Figure 6.18 The chloroplast, site of photosynthesis. Thylakoid Intermembrane space 1 m (a) Diagram and TEM of chloroplast

Stroma Inner and outer membranes Granum 1 m Figure 6.18aa Figure 6.18 The chloroplast, site of photosynthesis. 1 m

(b) Chloroplasts in an algal cell Figure 6.18b 50 m Chloroplasts (red) Figure 6.18 The chloroplast, site of photosynthesis. (b) Chloroplasts in an algal cell

Endosymbiont Theory 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 Chloroplast Nonphotosynthetic eukaryote Mitochondrion Photosynthetic eukaryote

peroxisome Peroxisomes are specialized metabolic compartments bounded by a single membrane Peroxisomes produce hydrogen peroxide and convert it to water How peroxisomes are related to other organelles is still unknown

1 m Chloroplast Peroxisome Mitochondrion Figure 6.19 Figure 6.19 A peroxisome.

Cell Separation

Centrifuged at 1,000 g (1,000 times the force of gravity) for 10 min Figure 6.4 TECHNIQUE Homogenization Tissue cells Homogenate Centrifuged at 1,000 g (1,000 times the force of gravity) for 10 min Centrifugation Supernatant poured into next tube Differential centrifugation 20,000 g 20 min 80,000 g 60 min Pellet rich in nuclei and cellular debris Figure 6.4 Research Method: Cell Fractionation 150,000 g 3 hr Pellet rich in mitochondria (and chloro- plasts if cells are from a plant) Pellet rich in “microsomes” (pieces of plasma membranes and cells’ internal membranes) Pellet rich in ribosomes

Homogenization Tissue cells Homogenate Centrifugation TECHNIQUE Figure 6.4a TECHNIQUE Homogenization Tissue cells Figure 6.4 Research Method: Cell Fractionation Homogenate Centrifugation

Centrifuged at 1,000 g (1,000 times the force of gravity) for 10 min Figure 6.4b TECHNIQUE (cont.) Centrifuged at 1,000 g (1,000 times the force of gravity) for 10 min Supernatant poured into next tube Differential centrifugation 20,000 g 20 min 80,000 g 60 min Pellet rich in nuclei and cellular debris 150,000 g 3 hr Figure 6.4 Research Method: Cell Fractionation Pellet rich in mitochondria (and chloro- plasts if cells are from a plant) Pellet rich in “microsomes” Pellet rich in ribosomes