The Wonders of the Cell The Cell

The Wonders of the Cell

The Cell

How to build a house: Atoms Elements Compounds and Molecules Sand/clay/water Bricks House

How to make a living creature: Atoms Elements Compounds/Molecules (ex. Lipids, carbs. , proteins, nucleic acids) Cells Living Creature

Little bit of cell history: • 1600 s Anton Van Leeuwenhoek • 1600 s Robert Hooke Cells

Little bit of cell history: • 1800 s – Robert Brown • 1800 s Cell Theory Nucleus

Cell Theory 1. All living things are made of cells • • Schleiden: all plants are made of cells Schwann: all animals are made of cells 2. Cells are the basic (smallest) unit of life (ie. Carry on the 8 life functions) 3. Cells can only come from preexisting cells (Virchow)

Problems? 1. Where did very first cell come from? 2. Viruses: Living or nonliving? Can you really call a virus a cellular organism?

• Viruses have no organelles • Just have DNA or RNA in a protein head • Uses all of host cell’s machinery • Can’t replicate without a host cell

Cell Types Prokaryotic Type • Simple Structure • Ancient (3 billion y. o. ) • Bacteria only Eukaryotic Type Complex Structure Relatively recent (1. 3 billion y. o. ) Plants and Animals More later!

Eukaryotic Cells • Animal Cell Structure

Organelles Nucleus: a. Cellular control center b. Surrounded by a nuclear membrane c. Holds Genetic Material d. Holds Nucleolus (Nucleoli)=have a role in ribosome synthesis e. Holds Nucleoplasm

Organelles Rough Endoplasmic Reticulum: a. Network of channels for transport of proteins b. butts up with nuclear membrane c. contains ribosomes

Organelles Ribosomes: a. synthesis proteins b. Large and small subunits c. Can remain free or dock with the ER (Bound ribosomes make proteins for export (ie. Secretory proteins) and cell membrane, Free ones make proteins for inside of cell

Let’s Take a Breather!

• DNA (Blueprints for proteins), doesn't leave nucleus

• Make a rough copy of segment of blueprints (m. RNA) • m. RNA leaves nucleus through nuclear pore

• m. RNA binds Free or ER ribosome • Ribosome makes protein

Organelles • Polypeptide injected into • Endoplasmic Reticulum

Protein folds in ER as it moves through the channels

Where To Now? Smooth ER: • Important in lipid synthesis for membranes • Steroid Synthesis • Calcium Storage

Where To Now? ER (Smooth or Rough) Transport Vesicle Golgi Complex

Where to next? Golgi Apparatus or Complex or Bodies: Stacks of flat sacs Processing, sorting, packaging, shipping, modifying proteins with carbs or lipids

What makes up the bulk of the cell? Cytoplasm (not an organelle) Mostly water Place where most organelles are found Place for chemical reactions

What powers this cell? Mitochondria: Performs cellular respiration= Converts sugar into energy “Powerhouse” of cell HAVE OWN DNA AND CAN REPLICATE INDEPENDENTLY

What happens to rejects and old stuff in cell?

The LYSOSOME

Lysosome • Has Hydrolytic Enzymes • Cellular Digestion Function • Can break down old organelles • Can be involved with defense • Can be involved with development

Autophagy (“self-eating”) House Cleaning • Pac-men-like globules gobble cytoplasm with worn out proteins and organelles and brings it to lysosome • Defense role against bacteria and viruses • Reduced Autophagy thought to lead to Tay Sachs, Alzheimer's, Parkinson's and Huntington’s Diseases

When things turn bad…. Apoptosis (-Greek: “falling apart”) • Cells that are worn out or no longer useful (ex. webbed fingers) kill themselves for greater good of body • Neighboring cells eat you and use your parts • Need a sequence of intracellular events and/or external signals for cellular death to happen

Organelles Vacuoles: • Small but numerous • Mainly in plants and protists • In animal cells • Storage functions (pigments, food, toxins, wastes) • Digestive functions • Water balance

Organelles • Peroxisomes – Similar to lysosomes – Break down substances – Produce a waste product, Hydrogen peroxide – Then then break it down

Vacuoles • Food Vacuoles • Contractile vacuoles

Vacuoles • Central Vacuole In plant cells – Storage – Water balance

Cytoskeleton: • Microtubules • Intermediate Filaments • Microfilaments

• Microtubules – Made of globular Tubulin Protein – Provide cell shape – Organelle anchors and molecular motors – Movement of cilia and flagella – Make up centrioles Click

• Intermediate Filaments – Anchorage and Reinforcement Rods inside Nucleus – Anchor Chromatin – Made of diverse fibrous proteins – Found in muscle, epithelial tissue, neurons, macrophages

• Actin filaments (Microfilaments) – Made of globular Actin Protein – Involved with cellular contraction – Involved in cell pinching – Facilitate Cyclosis

• Cytoskeleton Mini Movie

Centrioles: • Involved with cellular division • 2 barrel like structures • Located in centrosome region • Made of Microtubules • Not found in plant cells

Plastids: (Found only in photosynthetic cells) • Leucoplasts=storage site for nutrients • Chromoplasts=pigment storage sites – Ex. Chloroplast filled with chlorophyll – Site of Photosynthesis – Has own DNA and can replicate independently – GRANA and STROMA

Cilia and Flagella: • Cilia – Short, numerous – Involved with cell movement – Connected to cell via a basal body – Have a 9+2 microtubule arrangement

9+2 Arrangement in cilia Basal Body 9 triplet microtubule arrangement (like a centriole)

• Flagella – Usually 1 or 2 per cell – Long – Can be in front or back of cell – Connected via basal body – 9+2 pattern of microtubules – Note=Centrioles have a 9 Triplet Pattern

Plasma (cell) membrane: – Holds in cytoplasm – Selectively Permeable – Components: Phospholipids=Hydrophobic barrier Cholesterol=provide fluidity Proteins=transport (Channels/Carriers), receptors, enzymes, anchors Carbohydrates=cell signaling (self/nonself)

Fluid Mosaic Model of Plasma Membrane

Animal cells’ answer to absence of cell wall…. • Extracellular Matrix: – Network of fibrous collagen, and glycoproteins – Connected to cytoskeleton via Integrin proteins in membrane – Gives support, strength and resilience

More Complete Look at Model

Endomembrane System

Cell Junctions • Tight Junctions – Fused membranes – Force material through cells rather to sides • Gap Junction – Cytoplasm of cells connected through channel

Plant Cell vs. Animal Cell Plant Cell Wall Chloroplasts No Centrioles One, large vacuole

Cell Wall: a) In bacterial, yeast and plant cells b) Exterior to plasma membrane c) Provides shape and protection d) Made of cellulose in plant cells

Prokaryotic vs. Eukaryotic Revisited Prokaryotic Type Eukaryotic Type • Simple Structure Complex Structure • Ancient Relatively recent • Bacteria only Plants and Animals • No membrane-bound organelles • Many ribosomes (Don’t have membranes) • No Nucleus • Has Nucleiod Region

Origin of Eukaryotic Cell: Endosymbiotic Theory Mitochondria and Chloroplasts evolved from bacteria that were gobbled up by an ancient Cell. These organisms then lived inside the ancient cell and were a benefit to the ancient cell (endosymbiosis)

Proof of theory • Mitochondria and Chloroplast have own DNA • They can replicate independent • Same size as present bacteria • They have own ribosomes and are bacterial-like

Why don’t cells grow to infinity?

Why are most cells very small?

Surface Area to Volume Ratio • As a cell gets larger (ie. As its volume increases)…. • Volume increases proportionally larger than surface area

Long time to get rid of toxic wastes Getting nutrients in takes more time Too much volume for surface area to handle

Movement of materials into and out of the cell • Cell membrane selectively permeable – Maintains Homeostasis

What can cross the membrane freely? • Lipid-like molecules • Small uncharged molecules (ex. H 20, CO 2, 02, amino acids) • Some small molecules can cross freely but need a helper membrane transport protein (ex. Glucose) • Charged substances also need help to cross • Large molecules like polymers can’t cross

Current Research • Water flow across the membrane also facilitated by “aquaporin” channels

Mechanism for freely crossing: • Diffusion – Molecules move from a region of high concentration to a region of lower concentration until equilibrium – No energy needed – Need a concentration gradient to drive movement

Facilitated Diffusion • Passive-No Energy Needed but requires transport protein (ex. Glucose and ions) • Need gradient

Diffusion of water=Osmosis • Goes from high water concentration to a low water concentration • Or from a low solute concentration to a high solute concentration

Osmosis Solute

Effects of Osmosis: • Relative Terms: – Hypertonic= Contains more solute than something else – Hypotonic= Contains less solute than something else – Isotonic= Contains the same amount of solute as something else

Cell in hypertonic environment

Cell in Hypotonic Environment

Cell in Isotonic Environment

Animal Cells in Different Environment Lysed Cell Crenated Cell

Plant Cells in Different Environments a. k. a. Plasmolyzed

Active Transport • Requires Energy (ie. Need ATP) • Move materials against a concentration gradient

Active Transport-Pumps

Active Transport-Endocytosis • Endocytosis=transporting things into a cell – Ex. Pinocytosis=Taking small amounts of dissolved materials into the cell via vesicles – Ex. Phagocytosis=Taking large solid materials into a cell via food vacuoles

Pinocytosis (Nonspecific)

Phagocytosis (Nonspecific)

Receptor-Mediated Endocytosis Specific Uptake (ex. LDLs)

Active Transport-Exocytosis

• Cell mini movie

Cells and Living Creatures 1. Unicellular Creature • Ex. Protozoa, Bacteria, Algae

Cells and Living Creatures 2. Colonial Organisms • Individual cells loosely connected • No Specialization, they all are the same and act like independent unicellular creatures • Ex. Volvox

Cells and Living Creatures 3. True Multicellular Organisms =has many cells who divide the labor and perform specialized function =Each cell dependent on other cells =Cells organized into tissues

• Tissue=Cells similar and perform same function (Read section in SAT 2 Book) – Ex. Epithelial Tissue, Connective Tissue, Blood, Muscle, Nerve

• Organ=Group of different tissues working together for a common function – Ex. Stomach, pancreas, liver

• Organ System: Group of organs working for a common function – Ex. Digestive System, Nervous System