Nats 1610 Chapter 3
3.1: What is a cell?
A cell is built to carry out life functions efficiently
1. Every organism is composed of one or more cells
2. The cell is the smallest unit having the properties of life
3. All cells come from preexisting cells
All cells have 3 things in common they have:
1. Outer plasma membrane: Covering that encloses a cell’s internal parts
2. They contain DNA
3. Cytoplasm: The contents of a cell between the outer plasma membrane and the
Two basic kinds of cells:
1. Prokaryotic cells: Cell in which the DNA is not contained inside a nucleus;
bacteria are prokaryotic cells
2. Eukaryotic cells: Cells that have their DNA inside the nucleus.
Organelle: Any of the compartments and sacs inside a cell.
Surfacetovolume ratio: The physical relationship by which the volume of a growing 3D
object increases faster than its surface area does.
Lipid bilayer: Structure of the plasma membrane, in which two parallel layers of
phospholipids form with their heads facing outward and tails inward.
• “Self sealing”, prohibition of free edges
• Membrane lipid bilayer impermeability
3.2: Organelles of Eukaryotic Cells
Organelles isolate and physically organize chemical reactions in cells
Nearly all organelles have an outer membrane that separates the inside of the
organelle from the cytosol and the rest of the cytoplasm.
Organelles also provide separate locations for activities that occur in a sequence
Organelles with membranes:
Nucleus: protecting, controlling access to DNA
Endoplasmic Reticulum: Routing, modifying new polypeptide chains; synthesizing lipids.
Golgi body: Modifying new polypeptide chains; sorting, shipping proteins and lipids
Vesicles: Transporting, storing, or digesting substances in a cell.
Mitochondrion: Making ATP by sugar breakdown Lysosome: Intracellular digestion
Peroxisome: Inactivating toxins
Organelles without membranes:
Ribosomes: Assembling polypeptide chains
Centriole: Anchor for cytoskeleton
3.3: How do we see cells?
Microscopy: The use of a microscope to view objects, including cells, that is not visible
to the unaided eye.
Micrograph: The photograph of an image formed by a microscope.
3.4: The plasma membrane: A double layer of lipids
The plasma membrane controls the movement of substances into and out of cells.
The membrane is comprised of numerous proteins and lipids such as:
phospholipids, glycolipids, and cholesterol.
What makes the membrane fluid is movement of molecules in it.
Selective permeability: A property of the cell plasma membrane, in which the membrane
allows only certain substances to cross it.
3.6: The Nucleus
Nucleus contains and protects cells DNA, the genetic material.
Nucleus: Organelle that encloses a eukaryotic cell’s DNA.
Key functions: prevents DNA from getting tangled with structures in the
Nuclear envelope: A double membrane that separates the inside of the nucleus
from the cytoplasm. It has many pores.
Nucleolus: A cluster of the RNA and proteins used to assemble ribosomes from their
DNA is organized into chromosomes:
Chromatin: A cell’s DNA molecules and proteins attached to them
Chromosomes: An individual DNA molecule and attached proteins.
The nuclear envelope encloses the fluid part of the nucleus. Proteins embedded in
the envelopes two bilayers control the passage of molecules between the nucleus
and the cytoplasm. The nucleolus is where the parts of ribosomes form before passing into the cell’s
3.7: The endomembrane system
Endomembrane system: System of membrane bound cell organelles that mainly modify
new proteins, build lipids, and package the completed molecules.
Endoplasmic reticulum (ER): Channellike organelle. Lipids are assembled in smooth
ER. In rough ER, side chains are added to newly formed polypeptides.
Ribosome: Organelle where protein polypeptide chains are built.
Rough ER has many ribosomes and builds new cell proteins
Smooth ER has zero ribosomes and lipids are assembled and many proteins are
modified into their final form.
Golgi body: Series of flattened saclike organelles in which new lipids and polypeptide
chains are processed into their final form.
Vesicle: Small membrane bound sac in cells. Some vesicles transport substances, others