Class Notes (809,205)
United States (313,500)
BSC 108 (56)
Lecture 4

BSC 108 Lecture 4: Biology Chapter 4 Notes

9 Pages
Unlock Document

University of Alabama
Biological Sciences
BSC 108
Christina Yates

Biology Chapter 4 Notes A Tour of the Cell • If you stacked up 8,000 cell membranes, they would only be as thick as a textbook page. • The cells of a whale are about the same size as the cells of a mouse. • Every second, your body produces about 2 million red blood cells. Drugs That Target Bacterial Cells • Antibiotics were first isolated from mold in 1928. • The widespread use of antibiotics drastically decreased deaths from bacterial infections. • Most antibiotics kill bacteria while minimally harming the human host by binding to structures found only on bacterial cells. • Some antibiotics bind to the bacterial ribosome, leaving human ribosomes unaffected. • Other antibiotics target enzymes found only in the cells. Microscopes as Windows on the World of Cells • Light microscopes can be used to explore the structures and functions of cells. (for viewing living cells) • When scientists examine a specimen on a microscopic slide ➢ Light passes through the specimen ➢ Lenses enlarge, or magnify, the image • Two factors that determine the quality of microscopy: ➢ Magnification is an increase in the specimen’s apparent size. ➢ Resolving power is the ability of an optical instrument to show two objects as separate. Microscopes • Cells were first described in 1665 by Robert Hooke • The accumulation of scientific evidence led to the cell theory ➢ All living things are composed of cells ➢ All cells come from other cells • The light microscope is used by many scientists ➢ Light passes through the specimen ➢ Lenses enlarge, or magnify, the image • The electron microscope (EM) uses a beam of electrons ➢ Results in better resolving power than the light microscope • Two kinds of electron microscopes reveal different parts of cells ➢ Scanning electron microscopes (SEM) examine cell surfaces (for viewing surface features) ➢ Transmission electron microscopes (TEM) are useful for internal details of cells Features Common to All Cells • All cells have a plasma membrane – phospholipid bilayer – selective barrier • All cells have cytosol, or cytoplasm – the area within the membrane not including the organelles • All cells have at least one chromosome – containing DNA • All cells have ribosomes – sites of protein synthesis Two Major Categories of Cells • The countless cells on earth fall into two categories: ➢ Prokaryotic cells – Bacteria and Archaea ➢ Eukaryotic cells – plants, fungi, and animals • All cells have several basic features ➢ They are all bound by a thin plasma membrane ➢ All cells have DNA and ribosomes, tiny structures that build proteins. • Prokaryotic and eukaryotic cells have important differences ➢ Prokaryotic cells are older than eukaryotic cells ➢ Prokaryotes appeared about 3.5 billion years ago; eukaryotes about 2.1 billion years ago. Prokaryotes • Smaller than eukaryotic cells • Lack internal structures surrounded by membranes • Lack a nucleus • Have a rigid cell wall Prokaryotic Cell Walls • Prokaryotes have cell walls that are unique ➢ Bacterial walls are made up of peptidoglycan ➢ A target for antibiotics Membrane Structure • The plasma membrane separates the living cell from its nonliving surroundings. • The membranes of cells are composed mostly of ➢ Lipids ➢ Proteins • The lipids belong to a special category called phospholipids • Phospholipids form a two-layered membrane, the phospholipid bilayer • Membranes are not static sheets of molecules locked rigidly in place • Membrane phospholipids and proteins can drift about in the plane of the membrane • Tis behavior leads to the description of a membrane as a fluid mosaic: ➢ A high diversity of proteins exists within the membrane ➢ The proteins can move freely within the membranes Cell Surfaces • Most cells secrete materials that coat their outside surfaces ➢ External to the plasma membrane ➢ Helps protect and support cells • Many cells also have structures that facilitate interaction with their neighbors ➢ Cell junctions Plant Cell Walls • Plant cells have cell walls outside of their membranes ➢ Eukaryotic cell ➢ Protect the cells ➢ Maintain their shape ➢ Keeps the cells from absorbing too much water ➢ Made mostly of cellulose – a carbohydrate Animal Cells • Animal cells have an extracellular matrix ➢ This helps hold cells together in tissues and protects and supports them Structure and Function of the Nucleus • The nucleus is bordered by a double membrane called the nuclear envelope • Pores in the envelope allow materials to move between the nucleus and cytoplasm. • The nucleus contains a nucleolus where ribosomes are made • The nucleus is bordered by a double membrane called the nuclear envelope • Pores in the envelope allow materials to move between the nucleus and cytoplasm • The nucleus contains a nucleolus where ribosomes are made • Stored in the nucleus are long DNA molecules and associated proteins that form fibers called chromatin • Each long chromatin fiber constitutes one chromosome • The number of chromosomes in a cell depends on the species Ribosomes • Ribosomes are responsible for protein synthesis • Ribosome components are made in the nucleolus • Ribosomes may assemble proteins: ➢ Suspended in the fluid of the cytoplasm or ➢ Attached to the outside of an organelle called the endoplasmic reticulum • DNA directs protein production by transferring its coded information into messenger RNA (mRNA). • Messenger RNA exits the nucleus through pores in the nuclear envelope. • A ribosome moves along the mRNA translating the genetic message into a protein with a specific amino acid sequence The Endomembrane System: Manufacturing and Distributing Cellular Products • Several membranous organelles belong to the endomembrane system ➢ Endoplasmic Reticulum ➢ Golgi Apparatus ➢ Lysosomes ➢ Vacuoles ➢ Nuclear envelope The Endoplasmic Reticulum (ER) • The endoplasmic reticulum (ER)… ➢ Modifies an enormous variety of proteins that are first made on ribosomes ➢ Is composed of smooth and rough ER Rough ER • The rough appearance of parts of the ER is due to ribosomes that stud the outside of the ER membrane • The functions of the rough ER include the modification of: ➢ Membrane proteins ➢ Secretory proteins ➢ And the production of new membrane • After the rough ER synthesizes a molecule, it packages the molecule into transport vesicles Smooth ER • The smooth ER lacks surface ribosomes • It produces lipids, including steroids • It also is home to enzymes that detoxify foreign molecules ➢ Ex: drugs o As liver cells are exposed to a drug the amounts of smooth ER increases o Means the body will require more amounts of that drug to achieve the same effect The Golgi Apparatus • Works in partnership with the ER • Refines, stores, and distributes the chemical products of cells Lysosomes • A lysosome is a sac of digestive enzymes found in animal cells • Enzymes in a lysosome can break down large molecules such as ➢ Proteins ➢ Polysaccharides ➢ Fats ➢ Nucleic acids • Lysosomes have several types of digestive functions ➢ Many cells engulf nutrients in tiny cytoplasmic sacs called food vacuoles ➢ These food vacuoles fuse with lysosomes, exposing food to enzymes to digest the food ➢ Small molecules from digestion leave the lysosome and nourish the cell • Lysosomes can also ➢ Destroy harmful bacteria ➢ Break down damaged organelles Lysosomes and Disease • Several serious inherited disorders are the result of malfunctioning lysosomes ➢ Lysosomal storage diseases ➢ The lysosomes lack functioning enzymes o Undigested molecular accumulate o Ex: Tay-Sachs Disease ▪ Lipids build up in the brain Vacuoles • Vacuoles are membranous sacs that bud from the ➢ ER ➢ Golgi ➢ Plasma membrane • Contractile vacuoles of protists pump out excess water in the cell • Central vacuoles of plants ➢ Store nutrients ➢ Absorb water ➢ May contain pigments or poisons Review • The endomembrane system interconnects the: ➢ Nuclear envelope ➢ ER ➢ Golgi ➢ Lysosomes ➢ Vacuoles ➢ Plasma membrane Vacuoles • Vacuoles are membranous sacs ➢ Ex: contractile vacuoles of protists and ➢ Ex: central vacuoles of plants Chloroplasts and Mitochondria: Energy Conversion • Cells require a constant ener
More Less

Related notes for BSC 108

Log In


Don't have an account?

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.