Textbook Notes (363,339)
Canada (158,341)
Biology (1,137)
Biology 1225 (105)
Chapter 3

chapter 3 bio 1225 notes.docx

10 Pages
Unlock Document

Western University
Biology 1225
Michael Butler

Chapter 3 Cell Structure Section 3.1 Bacteria are found in all parts of the biosphere, including the human body. Huge numbers inhabit our intestines, but most of these are beneficial. A few can cause disease. Contamination of food with disease-causing bacteria can result in food poisoning that is sometimes fatal. 3.2 What exactly is a cell? Cell theory 1. Every living organism consists of one or more cells 2. The cell is the structural and functional unit of all organisms. A cell is the smallest unit of life, individual y alive even as part of a multi celled organism. 3. All living cells come from division of pre existing cells 4. Cells contain hereditary material, which they pass to their offspring when they divide. Cytoplasm – semifluid substance enclosed by a cell’s plasma membrane Nucleus – of a cell is an organelle with two membranes that holds the cell’s DNA Organelle – structure that carries out a special metabolic function inside a cell Plasma membrane – a cell’s outermost membrane Surface-to-volume ratio – a relationship in which the volume of an object increases with the cube of the diameter, and the surface are increases with the square. 1 1. Cells differ in size, shape and function, but all start out life with a plasma membrane, cytoplasm and region of DNA. Most cells have additional components 2. In eukaryotic cells, DNA is contained within a nucleus, which is a membrane-enclosed organelle. All cell membranes, including the plasma membrane and organelle membranes, are selectively permeable and consist mainly of phospholipids organized as a lipid bilayer. The surface-to-volume ratio limits cell size. 3. By the cell theory, a.) all organisms consist of one or more cells; b.) the cell is the smallest unit of life; c.)each new cell arises from another preexisting cell; d.) and a cell passes hereditary material to its offspring. Take Home Message How are all cells alike? 1. The cell is the fundamental unit of all life 2. All cells start life with a plasma membrane, cytoplasm and the region of DNA, which in eukaryotic cells only, is enclosed by a nucleus. The surface-to-volume ratio limits cell size and influences cell shape 3. Different types of microscopes reveal different aspects of cell structure 2 3.3 The structure of cell membranes Adhesion protein-plasma membrane protein that helps cells stick together Fluid mosaic – model of a cell membrane as a two dimensional fluid of mixed composition Receptor protein – plasma membrane protein that binds to a particular substance outside of the cell Recognition protein – plasma membrane protein that tags a cell as belonging to self (one’s own body of species) Transport protein – protein that passively or actively assists specific ions or molecules across a membrane 1. A cell membrane can be described as a fluid mosaic, which means it behaves like a two dimensional liquid of mixed composition – lipids (maily phospholipids) and proteins. 2. The lipids are organized as a double layer in which the nonpolar fatty acid tails of both layers are sandwiched between the polar heads 3. All cell membranes may have enzymes and transport proteins. 4. Plasma membranes can also incorporate receptor proteins, adhesion proteins and recognition proteins. Take home message What is a cell membrane? 1. The foundation of all cell membranes is the lipid bilayer: Two layers of phospholipids, tails sandwiched between heads. 2. Proteins that associate with lipid bilayers add various functions to a membrane. 3 3.4 Introducing Prokaryotic Cells biofilm - Community of microorganisms living within a shared mass of slime cell wall – semi rigid but permeable structure that surrounds the plasma membrane of some cells flagellum – long, slender cellular structure used for movement pilus – a protein filament that projects from the surface of some bacterial cells ribosome –organelle of protein synthesis 1. Bacteria and archaea informally grouped as prokaryotes are the most diverse forms of life. 2. These single celled organisms have no nucleus, but all have DNA and ribosomes. Many have a permeable but protective cell wall and a sticky capsule, as well as motile structures (flagella) and other projections (pili). 3. Bacteria and other microbial organisms often share living arrangements in biofilms Take home message How are bacteria and archaea alike? 1. bacteria and archaea do not have a nucleus. Most kinds have a cell wall around their plasma membrane. The permeable wall reinforces and imparts shape to the cell body 2. The structure of bacteria and archaea is relatively simple, but as a group these organisms are the most diverse forms of life. 4 3.5 Inside a Eukaryotic Cell Endoplasmic recticulum (ER) – organelle that is a continuous system of sacs and tubes extending from the nuclear envelope. Smooth ER makes lipids and breaks down carbohydrates and fatty acids; ribosomes on the surface of rough ER synthesize polypeptides Golgi body – organelle that modifies polypeptides and lipids, then packages the finished products into vesicles Mitochondrion – eukaryotic organelle that produces ATP by aerobic respiration Lysosome – enzyme filled vesicle that breaks down cellular wastes and debris Nuclear envelope –a double membrane that constitutes the outer body of the nucleus. Pores in the membrane control which substances can cross Peroxisome – enzyme filled vesicle that breaks down amino acids, fatty acids and toxic substances Vacuole – a fluid filled, empty looking organelle that isolates or disposes of waste, debris, or toxic materials Vesicle – small, membrane enclosed organelle; different kinds store, transport, or break down their contents Chloroplast – organelle of photosynthesis in the cells of plants and many protists Cilia – short movable structures that project from the plasma membrane of some eukaryotic cells. ** cilia are usually more profuse than flagella. The coordinated waving of many cilia propels cells through fluid and stirs fluid around stationary cells. 5 Eukaryotic flagella are structures that whip back and forth to propel cells such as sperm through fluid – they have a different structure and type of motion than prokaryotic flagella. Cytoskeleton – network of interconnected protein filaments that support, organize and move eukaryotic cells and their internal structures. Intermediate filament – stable cytoskeletal element that structurally supports cells and tissues Microtubule – cytoskeletal element involved in movement; hollow filament of tubulin subunits Motor protein – type of energy using protein that interacts with cytoskeletal elements to move the cell’s parts or the whole cell Pseudopod – a temporary protrusion that helps some eukaryotic cells move and engulf prey 1. All eukaryotic cells start out life with a nucleus and other organelles. 2.
More Less

Related notes for Biology 1225

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.