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