Textbook Notes (368,558)
Canada (161,962)
York University (12,849)
Biology (1,015)
BIOL 1000 (389)
Chapter 2

BIOL 1000 Chapter 2 - The Cell.docx

9 Pages
Unlock Document

BIOL 1000
Jennifer Steeves

Chapter 2 – The Cell 2.1 – Basic Features of Cell Structure and Function • Cell Theory  All living organisms are composed of cells  Cells are the structural and functional units of life  Cells arise only form the division of pre-existing cells • Divided into 2 parts – Cytoplasm and Genetic Material (Nucleus) • Cytoplasm – Cytosol, cytoskeleton, and organelles; bound by the plasma membrane  Proteins are made  Most other molecules required for growth and reproduction are assembled  Energy absorbed from the surroundings is converted into energy usable by cell • Plasma Membrane – a lipid bilayer in which transport proteins are embedded 2.2 – Prokaryotic Cells • Surrounded by a plasma membrane and (in most groups) enclosed in a cell wall • Cell Wall – composed of sugars and amino acids (collectively called peptidoglycan)  Provide strength, rigidity, and protection  Destruction of the cell wall can result in lysis of the cell • Capsule – Layer of polysaccharides surrounding the cell wall  Protects from extreme temperatures, desiccation antibiotics, viruses, and antibodies • Genetic material is typically a single circular DNA molecule  Located in the nucleoid – not separate from the cytoplasm • Cytoplasm contains masses of ribosomes • Appear simple in structure when compared in Eukaryotic Cells • Organisms with Prokaryotic Cells:  Have the greatest metabolic diversity of all organisms  Vastly out number all other types of organisms  Live successfully in almost all regions of Earth’s surface 2.3 – Eukaryotic Cells • Have a True Nucleus and Cytoplasmic Organelles enclosed within a plasma membrane Cytoplasm • Contains a remarkable system of membranous organelles • Contains Ribosomes and The Endomembrane System  Nuclear Envelope, ER, Golgi Complex, Lysosomes, Vesicles, Plasma Membrane • Cytosol – cytoplasmic solution surrounding the organelles  Energy metabolism & molecular synthesis  Performs specialized functions in support and motility Plasma Membrane • Lipid Bilayer (usually phospholipid) - -philic heads & -phobic tails  Through evolution many membranes derived from the same membrane • Various functions through several types of embedded proteins  Transport substances in and out of the cell  Receptors; trigger internal responses  Recognize & adhere to molecules on the surfaces of other cells  Important markers in the immune system; marking as “self” Cell Wall • Lies outside the cell membrane • Supportive cell, extracellular structure Nucleus • Contains much more DNA than the prokaryotic nucleoid • Contains chromatin – combination of DNA and proteins (histone and non-histone)  Distinct regions; Euchromatin and Heterochromatin  Euchromatin – loosely packed regions; genes active in RNA transcription  Heterochromatin – densely packed masses; genes are inactive • Eukaryotic DNA Packing – Histones  DNA wraps around a nucleosome (two molecules each of histones H2A, H2B, H3, H4)  Linker DNA connects adjacent nucleosomes  Binding of Histone H1 causes nucleosomes to package into a coiled structure (solenoid or 30nm chromatin fibre)  Histone proteins help pack DNA into highly coiled/compact structure • Eukaryotic DNA – Nonhistone Proteins  Proteins associated with DNA that are NOT histones  Involved in gene expression and regulation  Gene accessibility (loosening or tightening histone association)  Mostly negatively charged or neutral and come in a variety of sizes  Play a role in the expression of certain genes Nuclear Envelope • Separates the nucleus from the cytoplasm • Consists of two membranes; separated by a narrow space • Network of protein filaments, lamins, lines and reinforces the inner surface of the nuclear envelope in animal cells – type of intermediate filaments Nuclear Pore Complex • Large, octagonally symmetrical, cylindrical structure • Formed of many types of proteins; nucleoporins • Largest protein complex in the cell • Large molecules, RNA and proteins, pass through nuclear pores • Small molecules usually pass through unassisted Nucleolus • Formed from a specialized segment of chromatin • Ribosomal RNA molecules are made and combined with ribosomal proteins to make ribosomes Ribosomes • Free Ribosomes – present in the cytosol • Bound ribosomes – attached to the cytosolic side of membrane of ER • Prokaryotic:  Bacterial – Smaller than eukaryotic; protein synthesis is similar  Archaeal – size similar to bacterial; different structure; protein synthesis is a combination of bacterial and eukaryotic processes • Eukaryotes can begin translation only after the mRNa is exported from the nucleus (after transcription) Endoplasmic Reticulum • There are two forms: Rough ER & Smooth ER • Rough ER – Makes proteins that become part of cell membranes or are released from the cell  Ribosome studded • Smooth ER – Synthesizes lipids&steroids and breaks down toxic substances Sarcoplasmic Reticulum • Present in Muscles +2 • Stores Ca – released upon nerve impulse to cause the muscle cell to contract Golgi Complex • Vesicles from the Rough ER fuse with the cis face of the Golgi • Chemically modifies proteins made in the Rough ER & Sorts finished proteins  Post-translational modification – E.g. molecular tags added  Secretory vesicles released from the trans face of the Golgi  Secreted from the cell, Embedded in the Plasma Membrane, or included in Lysosomes Lysosomes • Specialized vesicles that contain hydrolytic enzymes; Digest:  Complex molecules such as food molecules that enter the cell by endocytosis  Cellular organelles that are no longer functioning correctly  Engulfed Bacteria  Cell Debris • Enzymes work best at an acidic pH (approximately pH = 5) • E.g. – Amoeba: Takes in Food particle by phagocytosis  Food vacuole (vesicle) fuses with lysosome for food digestion • E.g. – Microphages: Type of white blood cell involved in immune response  Engulfs invaders (e.g. bacteria) and delivers them to lysosome to be destroyed Mitochondria • Carry out cellular respiration – conversion of fuel molecules into the energy of ATP • Cristae increase surface area; Matrix contains enzymes, DNA, and free ribosomes Cytoskeleton • Supportive & Motility structure made from three Elements: 1. Microtubules – 25nm thick  Largest cytoskeletal element – microscopic rigid hollow tubes
More Less

Related notes for BIOL 1000

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.