Biology 1225 Chapter Notes - Chapter 3: Cellular Respiration, Membrane Protein, Protein Filament
5 Jun 2018
School
Department
Course
Professor
3: Cell Structure
Monday, May 21, 2018
2:37 PM
IMPORTANT CHAPTER FOR EXAM
3.1-- Food for Thought
o Gut bacteria helps with digestion
o Most common bacteria on warm blooded animals is E.Coli (most kinds are helpful but some can
be toxic)
o Many food products where toxic bacteria is found are sterilized by cooking and used as fillers in
products such as hamburgers, lunch meats, canned foods, etc.
Message: Lean finely textured meat (even though disgusting) was deemed perfectly sage to eat by the
USDA (US Department of Agriculture)
3.2-- What, Exactly, is a cell?
o Cell: smallest unit with the properties of life, main components are phospholipids arranged in a
bilayer
o We know cells carry out metabolism, homeostasis and reproduction on its own or part of an
organism (cells are alive)
The Cell theory
• Each organism consists of one or more cells
• The cell is the structure and function of all organisms and is individually alive
• All living cells arise by division of preexisting cells
• Cells contain DNA which they pass to their offspring
Components of a cell
• Plasma Membrane: Membrane that encloses a cell and separates it from the external
environment (consists mainly of phospholipid bilayer and is selectively permeable: only certain
materials can cross it)
• Cytoplasm: Semifluid substance enclosed by a cells plasma membrane (some/all cells
metabolism occurs in the cytoplasm and the cells internal components are suspended in it)
• Organelles: structure that carries out a special metabolic function inside a cell
• Nucleus: of a cell; an organelle with two membranes that hold the cells DNA
Constrains on Cell Size
• Surface to volume ratio: A relationship in which the volume of an object increases with the cube
of the diameter, and the surface area increases with the square (the bigger the surface area of a
plasma membrane, the more substances can cross it)
• When surface to volume ratio is applied to a round cell, the cell expands in diameter and
volume increases faster than its surface area
• If a cell gets too big, the inward flow of nutrients and outward flow of wastes across the
membranes will not be fast enough to keep the cell alive
find more resources at oneclass.com
find more resources at oneclass.com
How do we see cells?
o Unseen by the human eye
o In a light microscope, a sample can be seen
o All light travels in waves, this causes it to bend when passing through a curved glass lens (pg 48)
o Most cells are nearly transparent so their internal details may not be visible unless dyed or
stained.
o Researches will use light-emitting tracers to pin-point the location of a molecule of interest in a
cell
o Smaller structures need an electron microscope to be seen (electron microscopes use magnetic
fields as lenses to focus a beam of electrons onto a sample)
Message:
• All cells start life with a plasma membrane, cytoplasm, and a region of DNA. In Eukaryotic cells
only, the DNA is contained within a nucleus
• The surface-to-volume-ratio limits cell size and influences cell shape
• Different types of microscopes reveal different aspects of cell structure
3.3--Cell Membrane Structure ( Remember: Phospholipids have a phosphate containing head and 2
fatty acid tails)
o Foundation of all cell membranes is a lipid bilayer consisting of phospholipids
o The head of a phospholipid is highly polar and hydrophilic
o Its tails are hydrophobic
• Fluid Mosaic: Model of a cell membrane as a 2 dimensional fluid of mixed composition
Membrane Proteins
• Cell membranes physically separate an external environment from an internal one and are
associated with many proteins
• Each type of protein has a specific function
• Adhesion proteins: plasma membrane proteins that fasten cells together in animal tissue
• Receptor Protein: Membrane protein that triggers a change in cell activity in response to a
stimulus such as binding a certain substance
• Transport Proteins: Protein that moves specific ions or molecules across a membrane
• ALL CELL MEMBRANES INCORPORATE ENZYMES
Message:
• Foundation of cell membrane= lipid bilayer: two layers of phospholipids, tails sandwiched
between heads
• Proteins that associate with lipid bilayers add various functions to a membrane
3.4-- Introducing Prokaryotic Cells ( Remember: A polysaccharide is a long chain of monosaccharides;
a peptide is a shore chain of amino acids)
o Prokaryotes have protein filaments under the plasma membrane that reinforce the cells shape
o Ribosome: Organelle of protein synthesis (Cytoplasm of prokaryotes have ribosomes)
o Cell Wall: Semi rigid but permeable structure that surrounds the plasma membrane of some
cells
o Pilus: A protein filament that projects from the surface of some prokaryotic cells; help these
cells move across or cling to surfaces and transfer DNA from one cell to another
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Message: lean finely textured meat (even though disgusting) was deemed perfectly sage to eat by the. If a cell gets too big, the inward flow of nutrients and outward flow of wastes across the membranes will not be fast enough to keep the cell alive. How do we see cells: unseen by the human eye. Message: all cells start life with a plasma membrane, cytoplasm, and a region of dna. In eukaryotic cells only, the dna is contained within a nucleus: the surface-to-volume-ratio limits cell size and influences cell shape, different types of microscopes reveal different aspects of cell structure. 3. 3--cell membrane structure ( remember: phospholipids have a phosphate containing head and 2 fatty acid tails: foundation of all cell membranes is a lipid bilayer consisting of phospholipids, the head of a phospholipid is highly polar and hydrophilic. Fluid mosaic: model of a cell membrane as a 2 dimensional fluid of mixed composition.
