Atoms to Ecosystems Today: Biological Building Blocks: Our Cells! Reminders: Our fist lab is tomorrow, Wednesday. Be sure to bring and prepare your lab notebook! Our first group quiz is also tomorrow! It’s a “warm-up”, but be sure to review the material we work through today.

Your First Challenge: What sort of key functions will your space station need to support life? What types of structures might accomplish these functions? Form a group and design your space station using the whiteboards!

Comparing and Contrasting Prokaryotic and Eukaryotic Cells Quick “Think, Pair, Share”: Can you come up with three organisms that are made of prokaryotic cells? Three that are made of eukaryotic cells?

Prokaryotic Cell Structure

Basic Cell Structure: Eukaryotes

All Cells: The Plasma Membrane

Plasma Membranes: Phospholipids What do you notice about the structure of this molecule?

Plasma Membranes: Structure and Function

All Cells: Ribosomes Ribosomal RNA + Ribosomal Proteins = Ribosomal Subunits Each Ribosome composed of 2 subunits Ribosomes synthesize Proteins, may be free or bound

Eukaryotic Cells: The Nucleus

Eukaryotic Cells: The Nucleus Double-membrane envelope Envelope perforated by pores Pores lined with pore complex proteins Nuclear Lamina lines the inside of the envelope Network of filaments, the nuclear matrix, extends through interior

Within the Nucleus DNA is organized around proteins to form chromatin Ribosomal RNA synthesis occurs in the dense nucleolus

Eukaryotic Cells: The Endoplasmic Reticulum (ER) (Part of the Endomembrane System)

The Endoplasmic Reticulum ER is continuous with the nuclear envelope Composed of a systems of sacs called the cisternae, enclosing the cisternal space Can be smooth or rough Has Ribosomes! Manufactures proteins for excretion in transport vesicles, can serve as membrane factory No Ribosomes- Synthesizes lipids, detoxifies, aids in metabolism of carbohydrates, etc.

The Endoplasmic Reticulum

Eukaryotic Cells: The Golgi Apparatus (also part of the Endomembrane System)

Eukaryotic Cells: The Golgi Apparatus Vessicles transported to the Golgi after leaving the ER Composed of a stack of flattened membrane sacs called cisternae Each stack has two sides, the cis (receiving) face, and the trans (shipping) face Products labeled and modified while traveling from cis to trans

Lysosomes Membrane bound sac of hydrolytic enzymes pH = ~5 Important in Phagocytosis and Autophagy Also part of the Endomembrane System

Eukaryotic Cells: Vacuoles Any large vessicle may be called a vacuole Vacuoles are also part of the endo-membrane system

The Endomembrane System

Eukaryotic Cells: Mitochondria

Characteristics: Enclosed by two membranes: Outer is smooth, inner is folded into cristae This creates two spaces, the intermembrane space and the mitochondrial matrix Semi-autonomous! (Divide and reproduce; have their own DNA!)

Plant Cells: Chloroplasts Specialized Plastid containing the green pigment chlorophyll, enzymes, and other molecules for photosynthesis

Components & Terminology: Two membranes, separated by intermembrane space Internal system of flattened sacs called thylakoids A stack of thylakoids is called a granum Thylakoids are surrounded by fluid, the stroma, containing chloroplast DNA, ribosomes, and enzymes!!

Explaining the Origins of Mitochondria and Chloroplasts ??

Explaining the Origins of Mitochondria and Chloroplasts

Other Types of Plastids Found in Plants Chromoplasts Leucoplasts

Peroxisomes Specialized metabolic compartment Single membrane Transfer hydrogen to oxygen to make peroxide (toxic!) Peroxide broken down into water

Next: The Cytoskeleton A network of fibers extending through the cytoplasm Provides structural support, cell motility, and regulation

The Cytoskeleton 3 types of fibers: 1. Microtubles (thickest) 2. Microfilaments (thinnest) 3. Intermediate filaments

The Cytoskeleton: Microtubules In cytoplasm of all eukaryotic cells Hollow rods about 25 nm in diameter Made of the globular protein, tubulin

Functions of Microtubules Provide shape and support to the cell Serves as tracks along which motor proteins can move Help separate chromosomes during cell division Important components of cilia and flagella

Functions of Microtubules

Functions of Microtubules

Structure of Microtubules

Microtubules: Dynein walking in cilia and flagella (Structure and Function!)

Origins of Microtubules Microtubules often grown out from a centrosome (region near the nucleus) In animal cells, centrioles in the centrosome, give rise to microtubules

The Cytoskeleton: Microfilaments (#2) Also called actin filaments Solid rods (~7nm) of the globular protein, actin Each actin chain is twisted into a double chain

The Cytoskeleton: Microfilaments (#2) Structural role: bears tension Often form a network just inside the plasma membrane, supporting cell shape Play key roles in microvilli, muscle cell contraction, amoeboid movement, and cytoplasmic streaming

Microfilaments in Amoeboid Movement

Microfilaments in Cytoplasmic Streaming

The Cytoskeleton: Intermediate Filaments (#3) Diameter = 8-12 nm Bear tension Constructed of different types of keratins More permanent in the cell Secures nucleus, makes up the nuclear lamina

Connections to your Space Station? Help! We’re running out of coffee… Connections to your Space Station? Other Structures or Functions??

Next: Cell Surfaces What functions must ALL cell surfaces accomplish? What structural differences do you notice about these two cell types?

The Plant Cell Wall

The Cell Surface of Animal Cells No cell wall! Have an extracellular matrix (ECM) composed primarily of glycoproteins (esp. collagen) Another glycoprotein, fibronectin, attaches cells to the ECM by binding at receptor proteins (integrins). Integrins can transmit signals into the cell!

The Cell Surface of Animal Cells

Intercellular Junctions in Animal Cells 3 Types: 1. Tight Junctions: membranes fused, preventing leaking across a layer of cells 2. Desmosomes or anchoring junctions: connect cells in strong sheets (like rivets) 3. Gap Junctions: provide channels for small molecules to pass from one cell to the next

Intercellular Junctions in Animal Cells

The Dynamic Cell Membrane: Setting the Stage Hmm… I wonder what it’s made of?? In 1895, Charles Overton notices that lipid soluble compounds enter cells more readily.

Overton’s Hypothesis Confirmed Membranes made of lipids and proteins (1915) 1917- artificial membranes made from phospholipids 1925-Gorter and Grendel propose that the membrane is two molecules thick (a phospholipid bilayer) Needed a MODEL for how the molecules work together!

Model #1: The Davson-Danielli Model (1935) Two Problems: Not all membranes look alike! Membrane proteins usually have hydrophobic and hydrophillic regions

Model #2: The Fluid Mosaic Model (1972)

The Fluid Mosaic Model

The Fluid Mosaic Model

(Confirmed by Freeze-Fracture) The Fluid Mosaic Model (Confirmed by Freeze-Fracture)

The Fluid Mosaic Model

Origins of Membrane Proteins Result: Membranes have an “inside” and an “outside”