PACKET #15CHAPTER #6

Organelles of the Cell & How They Work Together

Introduction

Introduction

Organization of cells is basically similar in all cells.

Cells are typically small because of the relationship between surface area and volume.

Introduction II

As a cell increases in size, the ratio of volume (cytoplasm) to surface area (plasma membrane) increases. Microvilli increase the surface area without increasing

the volume.Cell shape & size are related to function.However, depending on the type of

eukaryotic cell, certain organelles may/may not be present.

Nucleus

Nucleus

Large structure surrounded by double membrane

Contains nucleous and chromosomes

Processes of DNA replication and transcription occur here

Nucleous

Granular body within nucleus

Consists of RNA and protein

rRNA produced hereAssembly of ribsome

subunits

Chromosomes

Composed of complex DNA and protein known as chromatin.

Contain genes that govern structure and activity of cell. Recall that a DNA

strand has segments that are called genes.

Nuclear Envelope

Controls “traffic” between the nucleus and the cytoplasm. Pores in the nuclear

membrane allow materials to pass in and out of the nucleus.

Cytoplasmic Organelles

Plasma Membrane

Encloses cell contentRegulates movement

of materials in and out of cell

Helps maintain cell shape

Communicates with other cells

Endoplasmic Reticulum

Major manufacturing center.Network of internal membranes extending

through cytoplasm.Synthesizes lipids and proteinsOrigin of intracellular transport vesicles that

carry proteins.

Smooth Endoplasmic Reticulum

Lacks ribosomes on outer surface.

Lipids are produced.Involved in drug

detox SER produces

detoxifying chemicals.

Rough Endoplasmic Reticulum

Ribosomes are found on the surface

Location for the manufacturing of proteins destined for secretion or for incorporation into membranes. Transcription

Ribosomes

Granules composed of RNA and protein

Some may attach to ER {forming the RER} while others float free in the cytosol Used in synthesis of

polypeptides (proteins) once attached to ER

Golgi Apparatus

Stacks of flattened membrane sacs.

Functions in the processing, sorting and modifying of proteins. Packages secreted

proteins—arriving from RER.

Processed product is passed to other organelles or to the plasma membrane.

The Golgi complex manufactures lysosomes.

Lysosomes

Compartments, in the form of membranous sacs, for digestion.

Contain enzymes to break down ingested materials, secretions and wastes.

Involved in apoptosis Programmed cell death.

Inappropriate apoptosis may be involved in cancer, AIDS and Alzheimer’s disease. Mutated genes allow for “deformed” lysosomes.

Involved in the metamorphosis of amphibians and some human diseases Rheumatoid arthritis and Tay-Sachs disease.

Vacuoles

Large fluid-filled membranous sacs that are mostly found in plant cells, cells of fungi and algae. Plant vacuoles allow cells

to increase in size. Protist vacuoles are

involved in digestion and excretion.

Store materials, wastes, water and maintain hydrostatic pressure.

Peroxisomes

Membranous sacs containing a variety of enzymes

Site of many diverse metabolic chemical reactions Perform redox reactions

That involve the making or splitting of hydrogen peroxide by the addition or removal of a hydrogen ion.

Mitochondria

Transform energy originating from glucose, lipids or proteins into ATP.

Mitochondria are double membrane bound. Matrix is inside of the inner

membrane. The intermembrane space is

between the two membranes. The inner membrane is a

particularly selective barrier. Cristae are the foldings of the inner

membrane, providing a large surface area.

Mutations in mitochondrial DNA have been linked to several genetic diseases.

Involved in apoptosis by activating capsules.

Plastids {Chloroplasts}

ATP and other energy-rich compounds are formed and then used to convert CO2 to carbohydrate.

Double membrane structure that encloses internal thykaloid membranes. Stroma is inside the inner

membrane. Inner membrane forms the

thylakoids. Arranged in stacks called grana. Thykaloid membranes contain

chlorophyll. Site of photosynthesis. Chlorophyll captures light energy. Chromoplasts contain pigments

and are common in petals and ripe fruit.

Cytoplasm/Cytoskeleton

Introduction

The cytoskeleton provides for cell shape and allows movement.

Microtubules

Hollow tubes composed of subunits of tubulin protein.

Provide structural supportPlay role in movement of cell and organelles.Play role in cell division.

Microfilaments

Solid, rod like structures composed of actin protein.

Provide structural support.Actin and myosin are the contractile units of

muscle cells.Play role in cell and organelle movement and

cell division.

Intermediate Filaments

Tough fibers composed of proteins.Help strengthen cytoskeleton.Stabilizes cell shape.

Centrioles

Pair of hollow cylinders located near the nucleus

Each centriole consists of nine microtubule triplets. (9 * 3 structure)

Mitotic spindle {spindle apparatus} forms between centrioles during animal cell division.

May anchor and organize microtubule formation in animal cells.

Absent in most plant cells.

Cilia

Short projections extending from surface of cell covered by plasma membrane composed of microtubules.

Used for movement in some unicellular organisms.

Used to move materials on surface of some tissues.

Flagella

Long projections made of peripheral microtubules.

Extend from surface of cell covered by plasma membrane.

Cell locomotion by sperm cells and some unicellular organisms.

Extracellular Matrix

Introduction

Surround most cells.Most eukaryotic cells

have a cell coat formed by molecules associated with the plasma membrane.

ECM & Animal Cells

Animal cells have extracellular proteins. Collagen

The main protein Fibronectin

Organizes the ECM Integrins

Membrane protein receptors

ECM, Plant Cells, Fungal Cells and Bacterial Cells

All may have cellulose-containing cell walls.Primary cell wall

Expands as the cell grows.Secondary cell wall

Formed between the primary cell wall and the cell membrane.

Middle Lamella Glues adjacent plant cells together.

Review & Differences Between Animal & Plant

Cells

Structure of Eukaryotic Cells

Plant Cells

Cellulose cell wall as well as cell membrane

Pits in cell wall Plasmodesmata present Large vacuole filled with cell sap Cytoplasm peripheral Nucleus usually peripheral Two cytoplasm membranes

Outer plasmalema; inner tonoplast

Variety of plastids Choloroplasts; leucoplast

Cilia and flagella absent in higher plants

Centrioles absent in higher plants

Animal Cells

No cellulose call wall, only membrane

No pits No plasmodesmata Same vacuoles but usually small

and numerous Cytoplasm throughout the cell

wall Nucleus anywhere in cytoplasm

but often central Only one cytoplasmic membrane Not normally any plastids Cilia common in higher animals Centrioles present

Animal Cell Plant Cell

Fig 6.9; Page 100