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Lecture 4

BIOL 1115 Lecture 4: Chapter 4B

5 pages93 viewsFall 2016

Course Code
BIOL 1115

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Guided Notes: Biology for Engineers
Chapter 4B: General Features of Cells
Material Covered:
* Includes tables and figures unless otherwise mentioned
4.1 Only figure 4.1 (note size differences virus, bacteria, ribosome, mitochondria, plant cell, human)
4.2 All (be sure to read genomes and proteomes connection)
4.3 All except Feature Investigation
4.4 All
4.5 All
o Cellular structures involved in producing polypeptides during the process of translation. The ribosome is
composed of two subunits, one small and one large. Each subunit contains one or more RNA molecules and
several types of proteins. Most of the RNA molecules that are components of ribosomes are made in the
vicinity of the nucleolus. The ribosomal proteins are created in the cytosol and then imported into the
nucleus through the nuclear pores. The ribosomal proteins and RNA molecules then assemble in the
nucleolus to form ribosomal subunits. Then the subunits exit through the nuclear pores into the cytosol
where they are needed for protein synthesis.
What comprises the two ribosomal subunits?
Why do cells vary in the number of ribosomes they contain?
o Example
Endoplasmic reticulum (ER)
o The endoplasmic reticulum is a network of membranes that form flattened fluid filled tubules, or
cisternae. The ER membrane encloses a single compartment called the ER lumen. There are two types
of ER, rough ER and smooth ER.
Are the above types of ER connected to each other?
Rough ER
Describe the ER
o The outer surface of the Rough ER is studded with ribosomes, giving it a bumpy appearance. It plays a key
role in sorting proteins that are destined for the ER, Golgi apparatus, lysosomes, vacuole, plasma
membrane, or outside the ell. Proteins are packages into the membrane vesicles and are moved from one
location in the endomembrane system to another.
o Another important function of the rough ER is the attachment of carbohydrates to proteins and lipids. This
process is called glycosylation.
What is found attached to the Rough ER?
What is the function of the Rough ER?
Smooth ER
What is the function of the Smooth ER?
o The smooth ER that does not have ribosomes functions in diverse metabolic processes.
o The extensive network of smooth ER membranes provide an increases surface are for enzymes that play
important metabolic roles.
o In liver cells, enzymes in the smooth ER detoxify many potentially harmful organic molecules including
barbiturate drugs and ethanol.
These enzymes convert hydrophobic toxic molecules into more hydrophilic molecules that are
easily excreted from the body.
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Guided Notes: Biology for Engineers
o The smooth ER in the liver cells also plays a role in carbohydrate metabolism. The liver cells of animals
store energy in the form of glycogen which is a polymer of glucose. Glycogen granules sit loosely to the
smooth ER membrane. When chemical energy is needed, enzymes are activated that break down the
glycogen to glucose-6-phosphate. Then an enzyme in the smooth ER called glucose-6-phosphatase
removes the phosphate group and glucose is exported from the cell into the bloodstream.
o The Smooth ER contains calcium pumps that transport calcium ions (Ca2+) into the ER lumen. The
regular release of CA2+ into the cytosol is involved in many of the vital cellular processes, including
muscle contraction in animals.
o The enzymes in the smooth ER are critical in the synthesis and modification of lipids.
Ex. The smooth ER is primary site for the synthesis of phospholipids.
o The enzymes in the smooth ER are necessary for the certain modification of the lipid cholesterol that are
needed to produce steroid hormones such as estrogen and testosterone.
Place the following within the table below:
Smooth ER
Rough ER
o Not studded with
o Stores calcium ions
o Detoxification
o Plays a role in synthesis of
o Studded with
o Carbohydrate
o Glycosylation
o Abundant in cells that
secrete proteins
Explain how the smooth ER play a role in detoxifying poisons such as drugs?
Golgi apparatus
o Preforms three overlapping functions
Protein sorting
Label and describe the image of the Golgi apparatus below
o Incoming transport vesicle
o Cis face
o Cisternae
o Lumen
o Secretory vesicle
o Trans face
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