Bio 8 Cells Unit 3

Discovery of Cell

• in 1665, Robert Hooke discovered cell, thought it looked like a slice of cork
• Cells are basic structures of organisms

Cell Theory

• 1. All living things are made of cells
• 2. Cells are basic units of life
• 3. New cells come from existing cells

Prokaryote and Eukaryote

• Prokaryote has one cell and no nuclueus
• Eukaryotes have many cells and at least one nucleus
• At some point contain DNA

Nucleus with Prokaryotes and Eukaryotes

• Nucleus is a large membrane enclosed strucutre that contains cell's genetic material
• Prokaryotes
• Have genetic material in nucleoid region, isn't contained in nucleus
• no membrane bound organelles, but have ribosomes
• have cell membrane, and most have cell wall that gives them shape Bacteria are prokaryotes

Nucleoid, Cell Wall, and Capsule

• Nucleiods are regions of the prokaryotic cell that contains DNA material, several proteins and enzymes that transcribe DNA and RNA and assist with cell growth and development
• Cell Wall is a tough, rigid structure, that is also porous to small molecules; its primary function, is to maintain cell shape and prevent bursting from osmotic pressure
• Capsule is found in some bacterial cells; found outside of cell wall; assists in retaining moisture, and helps cell adhere to surfaces and nutrients
• - Eukaryotic cells contain a nucleus in which their genetic material is seperated from rest of cell

Eukaryotic Cells

• Generally larger and complex than prokaryotic cells
• generally contain dozens of structures and internal membrane
• Many eukaryotic cells are highly specialized
• - - plants, animals, fungi, and protists are eukaryotes

Section 2 : Nucleus and Cytoplasm

• Structures within a eukaryotic cell that perform important fuctions known as organelles
• Biologists dividee the eukaryotic cell in to 3 major parts
• - Nucleus
• - Cytoplasm (includes all organelles and cytosol fluid
• - Cell membrane
• Plant and animal cells have 3 divisions, but plants also have a structure called cell membrane

Nucleus

• Control center for cell
• Contains the cell's DNA, which contains instructions for making proteins and other compounds
• Nucleus is surrounded by nuclear envelope composed of cell membranes which allows material in and out if the nucleus
• The granular material in the nucleus is chromatin (DNA is in loose form)
• Chromatin consists of DNA bound to protein
• When cell divides, chromatin condenses to form chromosomes
• Chromosomes contain genetic info that is passed from one generation to the next
• Nucleus contains nucleolus; is dark body near center of nucleus
• Ribosomes and RNA are produced in nucleolus

Cytoplasm and Ribosomes

• Cytoplasm
• Includes organelles and cytosol
• Cytosol : gel- like fluid in which the organelles are suspended
• Ribosomes
• Small particles of rRNA and protein
• Found either floating in the cytoplasm or attached to rough ER
• Ribosomes produce proteins by the following instructions in DNA
• - Cells are active in protein synthesis are often packed with ribosomes

Endoplasmic Reticulum (Smooth and Rough)

• Endoplasmic reticulum is where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell
• - 2 tyoes of ER- rough and smooth (differ in function, but are continuous with one another)
• Rough ER
• Ribosomes on the surface of rough ER
• Rough ER, produces and transports proteins, sending them to Smooth ER
• Smooth ER
• No ribosomes on the surface
• Performs tasks, such as synthesis of the membrane lipids and detoxification of drugs
• Packages proteins produced by rough ER and sends them to golgi body

Golgi Body

• Appears as a stack of closely apposed membranes
• Golgi body modifies, sorts, and packages proteins and other materials from the ER for storage in the cell or secretion outside of the cell
• From golgi body, proteins are shipped to final destinations either in cell or outside of the cell

Lysosome and Vaculoes

• Lysosome
• Small organelles filled with powerful enzymes
• They break down lipids, carbs, and proteins into small molecules that can be used by the rest of the cell
• Organelles that have lived out their usefulness
• Unwanted waste within the cell
• Vacuoles
• sac-like organelles that store materials such as H2O , salts, proteins, and carbs
• In many plant cells there is a single, large central vacuole filled with liquid
• Pressure of the central vacuole allows plants to support heavier structures such as leaves and flowers
• Vacuoles are also found in some unicellular organisms
• Paramecia contain a contractile vacuole that pumps excess water out of cell

Mitochondria and Chloroplasts

• Mitochondria (sg Mitochondrion)
• Nearly all eukaryotic cells contain mitochondrion
• Mitochondria converts chemical energy stored in food into cellular energy (ATP, adenosine triphosphate)
• Mitochondrion are enclosed by 2 membranes- inner and outer membranes
• Inner membrane is folded up inside organelle ; the folding is called cristae
• The cristae are covered in enzymes that convert nutrients into ATP (cellular energy)
• Chloroplasts
• Plants and some other organisms (like algae) contain chloroplasts
• Chloroplasts capture energy from sunlight and convert it into chemical energy in the process called photosynthesis
• Chloroplasts surrounded by 2 membranes
• Chloroplasts contain green pigment called chlorophyll

Endosymbiont Theory and Cytoskeleton

• Endosymbiont Theory
• An early ancestor of eukaryotic cells engulfed an oxygen-using prokaryotic cell
• Engulfed cell became an endosymbiont
• - Endosymbiont - cell living in another cell
• Over time, host cell and endosymbiont merged into single organisms
• Evidence : have double membrane, have own ribosomes and DNA, can reproduce on their own, independently of cell division
• Cytoskeleton
• network of protein filaments that help maintain cell shape
• Involved in movement
• Cytoskeleton is made up of :
• Microfilaments (smallest, maintain cell shape)
• Intermediate Filaments (medium, maintain cell shape and nucleus shape)
• Mircotubules (largest, invovled in cell division, and motility/movement

Microfilaments and Microtubules

• Microfilaments
• Thread like, made of actin
• Help maintain cell shape, help move cells (intracellular movement like muscle contraction)
• Microtubules
• Hollow structure, made of protein tubulin
• maintain cell shape
• Important in cell division (cytokinesis)
• build projections from cell surface (like cillia and flagella) that enable some cells to swim rapidly throughout liquids

Cilia and Flagella

• Cilia
• short brush like projections that move across cell's surface
• Flagella
• Long, whip like structure that help move cells (sperm cells)
• In animal cells, structures known as centrioles are located in across called centriosome
• Centricoles are located near nucleus and help organize cell division
• They form microtubule (tubulin) based spindle that will function in cell division