Chp 3 - Biology

Cell

the smallest unit of living things

• “Small room” 

• Building blocks of all living things

• Microscopic

• In Multicellular organisms, cells make tissues

• Prokaryotic

• Eukaryotic

2 different cell types

Robert Hooke

who discovered 1st cells from cork

37.2 Trillion cells

Humans have ___ in their bodies

 1 millimeter (mm) to 1 micrometer (μm)

Most cells range in size from ___ in diameter

large surface area

Cells need a ____ of the plasma membrane to adequately exchange materials (oxygen, CO2, food)

small

The surface-area-to-volume ratio requires that cells be

Large cells

surface area relative to volume decreases which also decreases the efficiency of transporting materials in & out of the cell

Small cells

larger surface area to volume ratio is advantageous for exchanging molecules with environment

1 billionth of a meter

1 nm (nanometer) =

1 millionth of a meter

1 μm (micrometer) =

1 thousandth of a meter (0.1 cm)

1 mm (millimeter) =

1/100th of a meter

1 cm (centimeter) =

39.37 inches; 100 cm in a meter

1 m (meter) =

Light or Compound

• microscope allow you to see 400x normally

  • Pass light through the specimen which passes through 2 lenses

  • Must be thin or translucent

  • Type of microscope normally found in a lab

  • Cell level structures

Dissecting

• microscope allows you to see 20-80x

  • 3D view

  • Many objects can be focused at one time

  • Tissue level structures

Electron Microscope

• Beam electrons, not light

• Highest magnification & resolution so better clarity

• Much more costly

Cell theory

a unifying concept in biology

• All Organisms are composed of cells

• All Cells are the basic units of structure & function in organisms

• All Cells come from preexisting cells b/c cells are self-reproducing

Schleiden, Schwann, Virchow

German Scientists who developed Cell Theory

Prokaryotic Cells

• Bacteria & Archaea

• Smaller -> 1.1 - 1.5 μm wide, 2 - 6 μm  long

• No nucleus or organelles

• Basic shapes: spirillum / spirochete, coccus, bacillus

• Nucleoid: Region is where DNA resides

  • DNA in the Nucleoid

• Plasmids: accessory DNA

Eukaryotic Cells

• Fungi, plants, animal, protists

• Larger -> 10 - 100 μm 

• Nucleus holds DNA, organelles perform functions

  • DNA in the Nucleus

• Specialize for specific function

Prokaryotic Cells

• Lack a membrane-bound organelle

• Structurally smaller & simpler than eukaryotic cells (which have a nucleus)

• Two taxonomic domains

  • Bacteria

  • Archaea

• Two prokaryotic domains are structurally similar but biochemically different

• 3 Bacterial Shapes: spirillum / spirochete, coccus, bacillus

• Cell Envelope includes:

  • Capsule

  • Cell Wall

  • Plasma Membrane

Structure of Prokaryotes - Outer Layers

Plasma Membrane

lipid bilayer w/ embedded & peripheral proteins

Cell Wall

maintains the shape of the cell & is strengthened by peptidoglycan (a polysaccharide)

Capsule

layer of polysaccharides on the outside of the cell wall. Also called a Glycocalyx

• Purpose is protection

• Well organized & resistant to removal - Protection

Phospholipid Bilayer (phosphate heads & fatty acid tails)

Structure of Prokaryotes - The Plasma Membrane

• Ribosome

• Flagellum

• Fimbriae

• Nucleoid

• Plasma Membrane

• Cell Wall

• Capsule

The Structure of Prokaryotes - A Prokaryotic Cell

• Cytoplasm 

  • Semifluid solution

  • Nucleoid

  • Plasmids 

  • Ribosomes

Prokaryotic Cytoplasm

Cytoplasm

Function: Gel like substance b/t the nucleus & edge of the cell

Semifluid solution

• Encased by plasma membrane

• Contains water, inorganic & organic molecules, & enzymes

Nucleoid

a region that contains the single, circular DNA molecule

Plasmids

small accessory (extrachromosomal) small rings of DNA - often assist in antibiotic resistance

Ribosomes

tiny structures in cytoplasm that synthesize (make) proteins

• Flagella

• Fimbriae

• Conjugation pilus

Prokaryotic External Structures

Flagella

provide motility / locomotion (ability for an organism to move independently by using metabolic energy)

Fimbriae

small, bristle like fibers on the cell surface that allow adhesion to surfaces

Conjugation pilus

rigid tubular structures used to pass DNA from bacterium to bacterium. Like a “sexual” transfer of DNA

Transfer of DNA from one bacterium to another

• Membrane-bound nucleus that houses DNA

• Organelles

• Plasma Membrane

• 1st two characteristics distinguish from prokaryotic cells 

• much larger than prokaryotic cells

Eukaryotic Cell Background / Contain

Plasma Membrane

Eukaryotic Cell Background

• Separates cell contexts from the environment

• Regulates passage of materials in & out

• Is composed of a phospholipid bilayer with embedded proteins

• What should leave & enter the cell

Endosymbiosis Theory

Theory of how Mitochondria & Chloroplasts Evolved + Origin of Organelles

Mitochondria & chloroplasts:

• SIMILAR in size to bacteria

• have circular DNA like bacteria

• have double membranes: outer from host membrane & inner from original prokaryote 

• have their own RIBOSOMES that are similar to bacterial ribosomes

Endosymbiotic Theory

Theory of Nucleus, Mitochondria, & Chloroplast Organelle Formation

• Cell Wall

• Ribosomes

• Cytoskeleton

Organelles WITHOUT Membrames

non-membrane-bound cell organelles

both in PROKARYOTIC & EUKARYOTIC CELLS

• Vacuole

• Lysosome

• Golgi Apparatus

• Endoplasmic Reticulum

SINGLE Membrane-Bound Organelles

only in a EUKARYOTIC CELL

• Nucleus

• Mitochondria

• Chloroplast

DOUBLE Membrane-Bound Organelles

only in a EUKARYOTIC CELL

• Nucleolus

• Nucleus

• Chromatin

• Endoplasmic Reticulum (ER)

  • Rough Er

  • Smooth Er

• Ribosomes

• Golgi Apparatus

  • Golgi Vesicule

• Vacuole

• Peroxisome

• Lysosome

• Centrosome

• Mitochondria

• Cytoplasm

• Plasma Membrane

• Cytoskeleton

  • Miicrofilament

  • Intermediate Filament

  • Microtubule

Eukaryotic Cell Organelles

Animal Cell

• Nucleolus

• Nuclear Envelope

• Nuclear Pore

• Nucleus

• Rough ER

• Smooth ER

• Golgi Complex

• Ribosome

• Centrosome

• Lysosome

• Perixisome

• Mitochondrion

• Cytoskeleton

  • Microfilament

  • Intermediate

  • Microtubule

• Cytoplasm

• Plasma Membrane

• Cilia

• Flagellum

Eukaryotic Cell Organelles

Eukaryotic Cells

• Animals, fungi, plants, protists (= single celled animals & plants)

• two classes of organelles

  • Endomembrane system

  • Energy Related Organelles

Endomembrane system

• Organelles that communicate with other another

  • Via membrane channels

  • Via small vesicles

Eukaryotic cell

• Mitochondria & Chloroplasts

• Independent & Self Sufficient

Energy Related Organelles

Nucleus

command center of the cell, usually near center separated from cytoplasm by nuclear envelope

• Consists of double layer of membrane

• Nuclear pores permit exchange b/t nucleoplasm & cytoplasm

• Contains chromatin (DNA / RNA) in semifluid nucleoplasm

• Dark Nucleolus

Nucleus

Function: Cell’s control center, contains DNA & genes

Chromatin

___contains nucleic acids & proteins

Condenses to form chromosomes

Chromosomes

• formed during cell division

• carriers of genetic information

Dark Nucleolus

• creates molecules of rRNA (ribosomal RNA)

• Function: Produces ribosomal subunits (ribosomes produce proteins)

• Chromatin

• Nucleoplasm

• Nucleur Envelope

  • Inner Membrane

  • Outer Membrane

• Double Membrane Phospholipid Membrane Nuclear Pores

Anatomy of the Nucleus

Ribosomes

• composed of rRNA (ribosomal RNA)

• Function: protein synthesis in the cell

• Consist of a large subunit & a small subunit

  • Subunits are made in nucleolus

• NOT TECHNICALLY AN ORGANELLE

Ribosomes

Located:

• On the endoplasmic reticulum

• Free in the cytoplasm

polyribosomes

Ribosomes either singly or in groups

• DNA info copied to mRNA (transcription)

• Ribosomes translate mRNA code into a sequence of amino acids to make a protein (translation)

  • Proteins synthesized by cytoplasmic ribosomes stay in cytoplasm; those by attached ribosomes end up in the Endoplasmic Reticulum

Ribosomes process of transcription & translation

Central dogma of molecular biology (ribosomes)

DNA-mRNA-protein sequence of events (DNA code copied by mRNA. mRNA takes that code to ribosomes in the cytoplasm. Code decoded to produce proteins)

Endomembrane System

• Series of intracellular membranes that compartmentalize the cell

• Restrict enzymatic reactions to specific compartments within cell

Endomembrane System

Components

• Nuclear envelope

• Membranes of Endoplasmic Reticulum (Rough & Smooth ER)

• Golgi apparatus

• Vesicles

  • Several types

  • Transport materials b/t organelles of system

Endoplasmic Reticulum

a system of membrane channels & saccules (flattened vesicles) continuous w/ the outer membrane of the nuclear envelope

Rough ER

• Studded with ribosomes on cytoplasmic side

• Proteins anabolism (synthesis)

  • Assists in synthesizing proteins

  • Modifies & processes proteins

    • Adds sugar to protein

    • Results in glycoproteins

      • Important in cell functions

  • Forms transport vesicles

    • Substances move to Golgi apparatus

Rough ER

Function: Responsible for protein synthesis & modification & transport vesicles

Smooth ER

• No ribosomes

• Synthesis of lipids (= fats)

  • In testes, hormone testosterone is produced by smooth ER

• Site of various synthetic processes, detoxification, & storage

  • The liver, with abundant smooth ER, detoxifies drugs

• Forms transport vesicles

  • Substances can move to Golgi apparatus

Smooth ER

Function: Manufacture of Lipids, synthetic processes, detoxification, storage, & transport vesicles

Golgi Apparatus

function: tags proteins & fats w/ proper labels for the cell to send them to the proper places

Golgi Apparatus

• Consists of flattened, curved saccules

• Resembles stack of hollow pancakes

• Modifies lipids & proteins with “signal” sequences (like adding an address to a package)

Golgi apparatus

• Modifies proteins & fats with a signal sequence so cell knows what to do with them

• Like Postal Service, FedEx, or UPS addresses packages for the cell

• So the cell knows where to send each package

Lysosomes

• Membrane-bound vesicles (not found in plants)

• Function: Break down old cellular components

• break down old cell parts for recycling

• Produced by the Gogli apparatus

• Contain powerful digestive enzymes & are highly acidic

Lysosomes

• Digest / break down large molecules into simpler subunits

• Recycle cellular resources

• In white blood cells they engulf pathogens (bad bacteria)

Peroxisomes

• Small round organelles that breakdown fatty & amino acids

• Function: Breakdown fatty acids & amino acids; detoxify poisons in the cell

• Found in the liver

Endomembrane System Summary

• Proteins produced in rough ER & lipids from smooth ER are carried in vesicles to the Golgi apparatus

• The Golgi apparatus modifies these products, then sorts & packages them into vesicles that go to various cell destinations 

• Secretory vesicles carry products to the cell membrane where exocytosis (substances leave / exit the cell) produces secretions

• Lysosomes also fuse with incoming vesicles & digest macromolecules

Chloroplasts

• Make Sugar from CO2 & Water

• Produce food (glucose) from light

• Oxygen is released as a byproduct

• Function: Produces glucose from sunlight

Mitochondria

• Break Down Sugar to CO2, Water & Energy

  • Break down sugars & other foods to produce energy

• Function: Cell’s energy production center

• Double Membrane -> Endosymbiotic theory

• Photosynthesis occurs in the thylakoids (hollow)

• Stacks of thylakoids forms granum

Chloroplast Structure

• Double Membrane System

• Cristae -> Folds in the inner membrane of a mitochondrion

• Allows greater surface area for ATP Production

Mitochondrion Structure

Cytoskeleton

• Maintains cell shape

• Assists in movement of cell & organelles 

• Makes internal transport possible

• Three types of macromolecular fibers

• Assemble & disassemble as needed

• May be compared to bones & muscles of animal

  • Is dynamic; responds to environmental changes

• Microfilament / Actin Filaments (smallest)

• Intermediate filaments

• Microtubules (largest)

Three types of macromolecular fibers in Cytoskeleton

Actin Filaments

• Extremely thin filaments, like twisted pearl necklace

• Support plasma membrane

• Support for microvilli in intestinal cells

• Muscle contraction

Intermediate Filaments

• intermediate in size b/t actin filaments & microtubules

• Rope-like assembly of fibrous polypeptides

Intermediate Filaments

• Function:

  • Support nuclear envelope

  • Cell-cell junctions to keep cells in place

  • Keep organelles in place

  • Make skin tough

  • Form all hair 

Microtubules

• largest of cytoskeletal components

• Function:

  • Separate chromosomes in cell division

  • Organelles travel on microtubules around cell

• Formed by the ___ organizing center

The Centrosome is composed of 2 Centrioles at Right Angles to each other. Important in Cell Division

Microtubules - Centrosome & Centrioles

Microtubule Operation

• Energy is needed for movement from ATP

• Vesicle moves, microtubule doesnt move

Flagella

Hair-like projections from cell surface that aid in cell movement

Eukaryotic flagella

• In center are two single microtubules

• move like a propeller or cork screw

  • Ex: sperm cells in males

Cilia

• much shorter than flagella (tiny hairs projecting from cells)

• move in coordinated waves like oars

• found in Protists (one celled organisms for movement)

• Increase surface area in intestines to absorb more nutrients & water

  • Ex: Cells lining upper respiratory tract (in men & women), fallopian tubes in women

Intercellular Junctions

junctions connect cells in various ways

• Tight junctions

• Desmosomes

• Gap Junctions

• Plasmodesmata

Tight Junctions

stitch cells together

• Skin has many __ junctions to prevent things from getting in

• Line the urinary tract (you dont want urine to escape into your body)

Desmosomes

weld cells together. Keeps tissue in a sheet-like form

• heart, skin, muscles

Gap junctions

keep tissues together but allow particular substances through

• Ex: Heart - calcium moves from one cell to the next to make the heart beat in unison

Plasmodesmata

• are in plants only

• Function like gap junctions

• Allow signal molecules & nutrients to transport quickly

Animal Cells

• Only cell membrane

• No cell wall

• No defined shape

• Lysosomes

• Only Mitochondria, no Chloroplasts

• Gap Junctions b/t some cells

• Cilia & flagella present

Animal vs Plant Cell

Plant Cells

• Cell Wall + Membrane

• Defined cell shape

• No Lysosomes

• Chloroplasts & Mitochondria

• Plasmodesmata (= gap junctions)

• Central vacuole

• No cilia or flagella

  Animal vs Plant Cell

Plasma Membrane - Fluid Mosaic Model

• describes the components of the membrane

• in flux of patchwork of carbohydrates, proteins, cholesterol, phospholipids

• Phospholipids make up the membrane

• Proteins act as identifiers for the cell & gateways inside & out of the cell

  • Channel proteins: allows specific molecules in & out of the cell

• Cholesterol acts as an antifreeze

Phosphate

How the Membrane Reacts with Water

hydrophilic (water liking)

• Water inside & outside the cells interacts with the ___ heads

  • Hydrophilic substances cant move through the membrane easily b/c of the lipid layer