Cell TheoryVirchow, Schleiden and Schwann

1. Every organism is composed of one or more cells

2. Cells are the smallest units having properties of life

3. Continuity of life arises from growth and division of single cells

- Cells arise only from pre-existing cells.

How many cells in your body?

50 million million (trillion)

That’s 50,000,000,000,000 cells!!!!!!

And not only that, there are many different types.

Cells are diverse But only two basic types

Two Basic Cell Types

Prokaryote Eukaryote

NamePro = before

karyote = nucleusEu = true

karyote = nucleus

Relative size

very small large

True Nucleus present

No yes

Organelles Present

No Yes

DNA structure

loose, sometimes circular

packed into chromosomes

Examples Bacteria Plants, animals, protists

Prokaryotic Cell

Note the lack of nucleus, DNA free floating (nucleoid area)

DO HAVE plasma membrane, ribosomes, and cell wall (sometimes)

Endosymbiotic Theory

It is believed that eukaryotic cells arose from groups of prokaryotic cells living together.

Smaller ones inside larger ones.

EVIDENCE… For Endosymbiosis

Some eukaryotic organelles resemble bacteria

Mitochondria and Chloroplast – double membrane

Mitochondria and bacteria have similar size

Mitochondria and Chloroplast DNA circular like Bacteria

Mitochondria divide as bacteria do

Eukaryotic Cell

More Advanced, larger & have organelles

DO HAVE nucleus, ribosomes, mitochondria, chloroplasts (plants), cell wall (plants), endoplasmic reticulum, golgi complex, lysosomes, and vacuoles

Eukaryotic Cell

Lots of internal membrane-bound structures!

Why are cells so small?

Cells exchange all materials with their environment through the cell membrane.

Exchange is faster in a smaller cell.

Need a surface area proportional to their volume – Surface area to volume ratio decreases as cell gets larger.

Cells that are specialized for absorption have folds in plasma membrane to increase surface area

Plasma Membrane

Plasma Membrane

Both prokaryotic and eukaryotic cells have this “outer wall”

Holds the CYTOPLASM inside the cell

Gives cells their shape and flexibility

Helps to maintain HOMEOSTASIS by allowing substance to flow in and out of the cell – SELECTIVE PERMIABILITY

Structure of Plasma MembraneThe plasma membrane is a PHOSPHOLIPIID BILAYER

PHOSPHOLIPID BILAYER

Fluid Mosaic Model Phospholipids, cholesterol, and proteins all

flow like the surface of a wavy lake, moving and shifting.

Structure of Plasma Membrane

What are the structures and functions of the cell membrane?

Components of the Cell MembraneContains lipids, carbohydrates, and functional proteins

Phospholipid BilayerDouble layer of phospholipid molecules: hydrophilic heads—toward watery environment,

both sides hydrophobic fatty-acid tails—inside membrane

Membrane ProteinsIntegral proteins: within the membrane

Peripheral proteins: inner or outer surface of the membrane

CytoplasmAll materials inside the cell and outside the nucleus: cytosol (fluid):

dissolved materials: nutrients, ions, proteins, and waste products

organelles:

structures with specific functions

What are cell organelles & their functions?

Nonmembranous organelles: no membrane direct contact with cytosol

Membranous organelles: covered with plasma membrane isolated from cytosol

6 types of nonmembranous organelles: cytoskeleton microvilli centrioles

cilia ribosomes proteasomes

The CytoskeletonStructural proteins for shape and strength

Microfilaments Thin filaments composed of the

protein actin: provide additional mechanical strength interact with proteins for consistencyPairs with thick filaments of myosin for muscle movement

Intermediate Mid-sized between microfilaments

and thick filaments:durable (collagen)strengthen cell and maintain shapestabilize organellesstabilize cell position

Microtubules Large, hollow tubes of

tubulin protein:attach to centrosome

strengthen cell and anchor organelles

change cell shape

move vesicles within cell (kinesin and dynein)

form spindle apparatus

The Cytoskeleton

MicrovilliIncrease surface area for absorption

Attach to cytoskeleton

Centrioles in the Centrosome

Centrioles form spindle apparatus during cell division

Centrosome: cytoplasm surrounding centriole

Cilia PowerHair-like cilia move fluids across the cell surface

RibosomesBuild polypeptides in protein synthesis

Two types: free ribosomes in cytoplasm:

proteins for cell fixed ribosomes attached to

ER:proteins for secretion outside cell

ProteasomesContain enzymes (proteases)

Disassemble damaged proteins for recycling

Membranous Organelles5 types of membranous organelles: endoplasmic reticulum (ER) Golgi apparatus lysosomes peroxisomes mitochondria

Endoplasmic Reticulum (ER)endo = within

plasm = cytoplasm

reticulum = network

Cisternae are storage chambers within membranes

Functions of ERSynthesis of proteins, carbohydrates, and lipids

Storage of synthesized molecules and materials

Transport of materials within the ER

Detoxification of drugs or toxins

Smooth Endoplasmic Reticulum (SER)No ribosomes attached

Synthesizes lipids and carbohydrates: phospholipids and cholesterol (membranes) steroid hormones (reproductive system) glycerides (storage in liver and fat cells) glycogen (storage in muscles)

Rough Endoplasmic Reticulum (RER)Surface covered with ribosomes: active in protein and glycoprotein synthesis folds polypeptides protein structures encloses products in transport vesicles

Golgi ApparatusVesicles enter forming face and exit maturing face Secretory vesicles:

modify and package products for exocytosis

Membrane renewal vesicles:

add or remove membrane components

Transport vesicles:Carry materials to and from Golgi apparatus

Cis face, closer to ER

Trans face, closer to cell exit

LysosomesPowerful enzyme-containing vesicles:

lyso = dissolve, soma = body

Primary lysosome: formed by Golgi

and inactive enzymes

Secondary lysosome: lysosome fused

with damaged organelle

digestive enzymes activated

toxic chemicals isolated

Exocytosis Ejects secretory products and wastes

Lysosome Functions

Clean up inside cells: break down large molecules attack bacteria recycle damaged organelles ejects wastes by exocytosis

AutolysisSelf-destruction of damaged cells: auto = self, lysis = break lysosome membranes break down digestive enzymes released cell decomposes cellular materials recycle

PeroxisomesAre enzyme-containing vesicles: break down fatty acids, organic compounds produce hydrogen peroxide (H2O2) …TOXIC replicate by division

KEY CONCEPT

Cells: basic structural and functional units of life respond to their environment maintain homeostasis at the

cellular level modify structure and function

over time

Mitochondrion Structure

2 Membranes

Have smooth outer membrane and folded inner membrane (cristae)

Matrix: fluid around cristae

Mitochondrial FunctionMitochondrion takes chemical energy from food (glucose): produces energy molecule ATP

Nucleus

Nucleus

Control Center of the cell

Contain CHROMATIN (loose DNA) Bundles into CHROMOSOMES when cell is

ready to divide (it packs before moving)

Chromatin Chromosomes

Chromatin in the Nucleus

Directs PROTEIN SYNTHESIS (building proteins)

It contains the “blueprints” “Blueprints” are Called DNA DNA in loose coils called chromatin

How does the nucleus control the cell?

Nucleus: largest organelle

Nuclear envelope: double membrane

around the nucleus

Perinuclear space: between 2 layers of

nuclear envelope

Nuclear pores: communication

passages

Nucleus Controls Cell Structure and Function

Direct control through synthesis of: structural proteins secretions (environmental response)

Indirect control over metabolism through enzymes

Within the NucleusDNA: all information to build and run organisms

Nucleoplasm: fluid containing ions, enzymes, nucleotides,

and some RNA

Nuclear matrix: support filaments

Nucleoli in NucleusAre related to protein production

Are made of RNA, enzymes, and histones

Synthesize rRNA and ribosomal subunits

Organization of DNA

Figure 3–11

Nucleosomes: DNA coiled around

histones

Chromatin: loosely coiled DNA

(cells not dividing)

Chromosomes: tightly coiled DNA

(cells dividing)

DNA and GenesDNA: instructions for every protein in the body

Gene: DNA instructions for 1 protein

What is genetic code?

Genetic CodeThe chemical language of DNA instructions: sequence of bases (A, T, C, G) triplet code:

3 bases = 1 amino acid

KEY CONCEPT

The nucleus contains chromosomes

Chromosomes contain DNA

DNA stores genetic instructions for proteins

Proteins determine cell structure and function

Cell Walls

Outside of the plasma membrane

Can be made of thick fibers of cellulose (plants), chitin (fungi), or peptodoglycan (some bacteria)

Plant cells have openings in cell wall called GAP JUNCTIONS for cell to cell communication

Animal cells DO NOT have cell walls

Cell Wall of Plants

Is this a prokaryotic or eukaryotic cell?