Chapter 6Introduction to Cells

COMMON CELL TRAITS

A cell is the smallest unit that is capable of performing life functions.

All organisms are made of cells

COMPARING CELLS

The size & shape of a cell relates to its function. (job it does)

TYPES OF CELLS

Every organism is one of TWO TYPES of cells– PROKARYOTIC (Pro- before) (Karyon-

Kernel) In Prokaryotic cells, the DNA is

concentrated in a region called the NUCLEOID with no membrane separating it from the rest of the cell

TYPES of CELLS

– EUKARYOTIC (Eu- true) (Karyon -Kernel)

Has a true NUCLEUS, bounded by a membranous nuclear envelope

SIZE

Prokaryotic cells are smaller than Eukaryotic– Mycoplasmas (bacteria) = smallest cells

between 0.1 and 1.0 Micrometers in diameter

– Most bacteria are 1-10 Micrometers

Eukaryotic cells are 10-100 Micrometers in diameter

Found in all cells

All cells have several basic features in common:

They are all bounded by a PLASMA MEMBRANE (thin skin). This membrane is a selective barrier that allows sufficient passage of Oxygen, Nutrients, and waste.

Within the membrane, is a semi-fluid substance called CYTOSOL (jelly-like)

Found in all cells

ALL cells contain CHROMOSOMES- carrying genes in the form of DNA

All cells have RIBOSOMES- Tiny organelles that make proteins

The interior of the cell- from the Plasma membrane to the Nucleus (Nucleoid) is called the CYTOPLASM

Prokaryotic Cells(proh KAYR ee yah tihk)

cells without membrane-bound structures

EX: bacteria pond scumOnly the DOMAINS

Bacteria and Archaea consist of Prokaryotic cells

Eukaryotic Cells(yew KAYR ee yah tihk)

cells with membrane-bound structures

EX: animals, plants, fungi and protists

NUCLEUS

Directs all cell activities Contains instructions

for everything the cell does

These instructions are found on a hereditary material called DNA

Usually the largest organelle

DNA & Chromosomes

In the nucleus, DNA is organized into discrete units called CHROMOSOMES- that carry genetic material

Each CHROMOSOME is made up of CHROMATID- a complex of proteins and DNA

NUCLEAR ENVELOPE

separates nucleus from cytoplasm

controls movement of materials in & out of nucleus

Is a DOUBLE membrane- each a lipid bilayer with associated proteins

NUCLEOLUS

Aka “little nucleus” Found in the nucleus Ribosomal RNA (rRNA)

is synthesized from instructions in the DNA

Some Proteins are assembled by rRNA in the Nucleolus

RIBOSOMES-Protein Factories

Made up of Ribosomal RNA (rRNA) and Protein

Carry about Protein Synthesis (make Proteins)

Build Proteins in two locations..

RIBOSOMES

* FREE RIBOSOMES are found floating in the CYTOSOL- proteins made here function within the cytosol

* BOUND RIBOSOMES are found on the outside of the Endoplasmic Reticulum (ER)

Chapter 6.4 Endomembrane System

Carries out a variety of tasks in the cell such as:

Synthesis of proteins and their transportation

Metabolism and movement of lipids

Detoxification of poisons

Includes: Nuclear Envelope Endoplasmic Reticulum

(ER) Golgi Apparatus Lysosomes Vacuoles Plasma Membrane

Endoplasmic Reticulum: Biosynthetic Factory

Endoplasmic =“within the cytoplasm”

Reticulum = “Little Net” A network of

membranous tubules and sacs called Cisternae

Smooth and Rough ER

Functions of Smooth E.R.Smooth= Lacks Ribosomes

Smooth= Lacks Ribsomes Enzymes of the smooth E.R. are important

to: – Synthesis of Lipids (oils, phospholipids,

Steroids)– Sex Hormones of Invertebrates – Detoxify drugs and poisons– Stores Calcium Ions

Functions of Rough E.R.Rough= Contains Ribosomes

Many types of specialized cells secrete proteins produced by Ribosomes attached to the rough E.R.

GLYCOPROTEINS- Proteins that have Carbohydrates covalently bonded are attached to the protein in the E.R. by specialized molecules built into the ER membrane

Transport Vesicles

Golgi Apparatus- Shipping and Receiving Center

After leaving the ER, many transport vesicles travel to the Golgi Apparatus

Golgi is a center for manufacturing, warehousing, sorting and shipping

In the Golgi, products of the ER are modified and stored and then sent to other destinations

Golgi Apparatus

Consists of flattened membranous sacs - CISTERNAE

The membrane of each cisterna in a stack separates its internal space from the Cytosol

Golgi Apparatus

Products of the ER are usually modified during their transit in the Golgi Apparatus

In addition to modifying products, the Golgi Apparatus manufactures certain macromolecules by itself

Macromolecules such as: Polysaccharides, including Pectins

Lysosomes

A membranous sac of hydrolytic enzymes that an animal cell uses to

digest all kinds of macromolecules

Contain acidic enzyme to break down wastes

Excessive leakage from a large number of lysosomes can destroy a cell by autodigestion

Lysosomes

Hydrolytic enzymes and Lysosomal membrane are made by rough ER and then transferred to the Golgi apparatus for further processing

Lysosomes carry out intracellular digestion in a variety of circumstances

Phagocytosis (Phagein- to eat) (Kytos-Vessel)

Amoebas and other protists eat by engulfing smaller organisms by phagocytosis

The food vacuole formed this way then fuses with a lysosome, whose enzymes digest the food

Digestion products, including simple sugars, pass into the cytosol and become nutrients for the cell

Autophagy

Lysosomes use their hydrolytic enzymes to recycle the cell’s own genetic material- AUTOPHAGY

During Autophagy, a damaged organelle or small amount of cytosol becomes surrounded by a membrane and a lysosome fuses with this vesicle

With the help of Lysosomes, the cell continuously renews itself

Tay-Sachs Disease

Example of Lysosomal storage disease:

A lipid-digesting enzyme is missing or inactive, and the brain becomes impaired by an accumulation of lipids in the cells.

Vacuoles- Diverse Maintenance Compartments

In plant or fungal cells- similar to Lysosomes in animal cells

Food Vacuoles- formed by Phagocytosis Contractile Vacuoles- pump excess water out

of the cell, maintaining the appropriate concentration of salts and other molecules

Central Vacuole

Enclosed by a membrane called the TONOPLAST- selective in transporting solutes

Central Vacuole- holds reserves of important organic compounds such as proteins

Plant’s cell main repository of inorganic ions, such as potassium and chloride

Disposal sites for metabolic by-products Some contain pigments or poisons

Chapter 6.5- Mitochondria and Chloroplasts

In Eukaryotic Cells, Mitochondria and Chloroplasts are the organelles that convert energy to forms that cells can use for work

MITOCHONDRIA- are the sites of cellular respiration, the metabolic process that generates ATP by extracting energy from sugars, fats and other fuels with the help of oxygen.

Mitochondria

Enclosed by two membranes- a phospholipid bilayer with embedded proteins

Outer membrane-smooth

Inner membrane is convoluted- with infoldings called CRISTAE

ATP is made in inner membrane

Highly folded- for large surface area for more protein contact

Chloroplasts

Found only in plants and algae, are the sites of PHOTOSYNTHESIS

They convert solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from Carbon Dioxide and Water

Chloroplasts- Capture of Light Energy

Amyloplasts- colorless plastids that store starch

Chromoplasts- have pigments that give fruits and flowers their color

Chloroplasts- contain CHLOROPHYLL- for photosynthesis

Chloroplasts

Contain- THYLAKOIDS are stacked like poker chips

Each stack is called a GRANUM

The fluid outside of the Thylakoids- is the STROMA

Stroma contains the chloroplast DNA and Ribosomes as well as many enzymes

Peroxisomes- Oxidation

Contain enzymes that transfer hydrogen from various substrates to Oxygen, producing Hydrogen Peroxide as a by-product

These reactions have different functions- may break down fatty acids, may detoxify alcohol and other harmful compounds by transferring Hydrogen from the poisons to Oxygen

Chapter 6.6- CYTOSKELETON

A network of fibers extending throughout the cytoplasm- plays a major role in organizing the structure and activities of the cell

Gives structure and is also involved in several types of cell motility

protects the cell gives shape is made of cellulose A cell wall is found in plants, algae, fungi, & most

bacteria.

CELL WALL

CELL MEMBRANE

Outer covering, protective layer around ALL cells

For cells with cell walls,the cell membrane is inside the cell wall

Allows food, oxygen, & water into the cell & waste products out of the cell.

CYTOPLASM

gelatin-like inside cell membrane constantly flows aka protoplasm

CYTOSKELETON

scaffolding-like structure in cytoplasm

helps the cell maintain or change its shape

made of protein

CHROMATIN

contains genetic code that controls cell made of DNA & proteins