Two main types of cells

Prokaryotic – no nucleus, no membrane-bound organelles

Eukaryotic – has a nucleus, has membrane-bound organelles

An Overview of Cell Structure

All cells have three components Cell/plasma membrane Genetic material Cytoplasm/cytosol

The Plasma Membrane

The Plasma Membrane Surrounds the Cell

Phospholipid bilayer contains embedded proteins

The Plasma Membrane Surrounds the Cell

Proteins enable cell to interact with environment

Transport proteins facilitate passage across membrane

Receptors induce cell changes with contact by molecules

Markers provide cell identity

The Central Portion of the Cell Contains the Genetic Material

Genetic material in prokaryotes

Single, circular molecule of DNAIs concentrated in the center, not membrane

bound

Genetic material in eukaryotes

Contained within the nucleusSurrounded by two membranes

The Cytoplasm Comprises the Rest of the Cell's Interior

Cytoplasm is a semifluid matrixContains chemicals to carry out growth and

reproduction

The Cell Theory

Robert Hooke

First cells seen with invention of microscope in 1665

Observed honeycomb of empty compartments in cork

Antonie Van Leeuwenhoek

First to observe living cells

Matthias Schleiden

Observed plant tissues

Theodor Schwann

Observed animal tissues

Modern principles of cell theory

All organisms composed of one or more cells

Cell is smallest living functional unitCells arise only from the division of other

cells

The Structure of Simple Cells: Bacteria (Prokaryotic)

A. Simplest Cellular Organisms

Great diversitySimilar organization, small sizeMay adhere in masses, but are

fundamentally separate from one another

B. Strong Cell Walls

Carbohydrate matrix cross linked with peptide units

Gram positive, thick cell wall, retains stain, purple

Gram negative, thinner cell wall, releases stain, red or pink

The Prokaryotic Cell

C. Simple Interior Organization

1. Lack internal compartmentalization a. Cell strength due to cell wall b. Reactions not separated, single metabolic

unit

2. Lack membrane-bound organelles less efficient metabolic functions

The Structure of Eukaryotic Cells: An Overview

Plants, animals, fungi and protists are all eukaryotic

Eukaryotes are more complex than Prokaryotes

Eukaryotes Are More Complex Than Prokaryotes

Hallmark is compartmentalization Organelles are separated from one another by

membranes

The Animal Cell

Eukaryotes possess internal membrane-bound organelles

Golgi complex and lysosomes created by folding endoplasmic reticulum

Mitochondria and chloroplasts associated with cellular energy

Eukaryotes possess internal membrane-bound organelles (cont).

Central vacuole in plants stores protein and wastes

Vesicles in animals store and transport many materials

Nucleus contains chromosomes made of DNA

The Plant Cell

Plant Cells

Cytoskeleton-An internal scaffold of proteins

Cell walls-Cellulose fibers embedded with polysaccharides and proteins

The Endoplasmic Reticulum

Thin membranes not visible in light microscope

Divide interior into compartmentsLipid bilayer with embedded proteinsAbbreviated ER

Endoplasmic Reticulum(ER)

Rough ERSmooth ER

Rough ER: Manufacturer of Proteins for Export

Ribosomes assist in the manufacturing of proteins They contain groups of proteins and RNA Translation of RNA into proteins

Smooth ER: Organizer of Internal Activities

Lack ribosomesContain embedded enzymesAssociated with detoxification,

carbohydrate and lipid synthesis

The Nucleus: Information Center for the Cell

Spherical appearance in most cellsIt is the largest organelle, readily visibleCentrally located, positioned by filaments

The Nucleus

The Nuclear Envelope

Double layer of membranes, outer membrane continuous with ER

Membranes pinched together at nuclear pores Embedded with proteins, serve as molecular

channels Restrict passage of molecules to proteins and

RNA

Proteins are made on the Ribosomes

On the ribosome, RNA is made into proteins

Proteins are necessary for the function of life Ribosomes are the worker bees of the cell

The Golgi Complex: The Delivery System of the Cell

Golgi Bodies Individual, flattened stacks of membranes Collectively called the Golgi complex Function in Molecule Collection, Packaging,

Distribution The FedEx of the cell

The Golgi Complex

Lysosomes: Producers of digestive enzymes for the cellMembrane bound organelles containing digestive

enzymes Digest worn-out cell components and recycle material

into new structures

Digest pathogens engulfed by white blood cells The garbage truck of the cell

Participate in selective cell annihilation

Lysosomes

Centrioles: Microtubular Assembly Plants

Present in animal and protist cellsOccur in pairs at right angles near nuclear

envelope, forms the centrosome Associated with assembly and organization

of microtubules Help move DNA during Mitosis

Centrioles

Mitochondria: The Cell's Chemical Power Plant

Occur in all organisms Bounded by double membrane

a. Outer membrane is smooth b. Inner membrane is folded into contiguous

layers called cristae

Mitochondria possesses own DNAMitochondria are capable of replication

Mitochondria

Chloroplasts: Where Photosynthesis Takes Place

Occur in photosynthetic organisms, plants and algae

Bounded by double membraneInternal membranes form disk-shaped

thylakoids (look like pancakes)Photosynthetic pigments on thylakoid surfacePossess own DNA, can reproduce

Chloroplast

The Cytoskeleton

Interior Framework of the Cell

Flagella and Cilia

Motility for the Cell

Flagella vs. Cilia

Cilia

Have functions other than locomotionPass fluids over tissue surfaceBend in response to sound waves

In your aural canal

ENDOSYMBIONT HYPOTHESIS

Mitochondria and chloroplasts originally were independent prokaryotic cells (with their own DNA).

Were engulfed by larger cells, eventually became symbiotic with each other.