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What structures are found in the nucleus?
chromosomes, long linear molecules of DNA that contain the genetic info
Where are proteins made
ribosomes
Where are ribosomes found
free in the cytoplasm or attached to the rough endoplasmic reticulum
What kind of covalent bonds are needed to make a protein?
amide bonds (peptide bonds while connecting amino acids)
What are ribosomes made out of?
RNA and protein
How are ribosomes constructed?
rRNA forms the core of the ribosom’es structure and is the actual catalytic molecule that speeds the formation of amide/peptide bonds in the protin
Which part of the ribosomes forms its core?
rRNA
Which part of the ribosome catalyzes the formation of peptide bonds in the protein?
rRNA
What is the order of events of protein synthesis?
mRNA transcribed in the nucleus, mRNA exits through nuclear pores, mRNA meets small subunit of the ribosome in the cytoplasm, the mRNA and small subunit, and the mRNA is translated into protein.
The sequence of amino acids in the protein is determined by the sequence of
nucleotides in the mRNA, which was copied from the sequence of the DNA
What are the subdivisions of the endomembrane system?
i. endoplasmic reticulum
ii. golgi complex
iii. membrane-bound vesicles
Membrane bound vesicles
transport materials between parts of the system
Functions of RER
synthesis of proteins destined for the membrane, for export (secretion), and for other organelles. proteins are synthesized by ribosomes on the RER, which segregates all of the protein or part of it inside the lumen of the RER after synthesis
Functions of SER
synthesize the membrane components phospholipid and cholesterol, and to detoxify foreign substances, much as drugs and toxins
How do Golgi and ER function together?
they are a system for synthesize proteins and lipids and directing them to their correct location of the cell. Protein and lipid material starts in the ER and moves to the cis face of the Golgi via transport vesicles
Golgi functions
further modifies proteins whose modification starts with the ER. Also sorts proteins by their eventual destination
Steps of the pathway for secreted proteins
RER, transport vesicles, sacs of the cis Golgi, sacs of the trans Golgi, secretory vesicle, and fuse with plasma membrane, releasing contents in a process called “exocytosis”
Endocytosis
process of bringing bulk materials into the cell
Exocytosis
the process of ejecting bulk materials from the cell
Different kinds of endocytosis
phagocytosis, pinocytosis
Phagocytosis
cell eating
Pinocytosis
cell drinking
Properties of Lysosomes
have an acidic pH and a set of digestive, hydrolytic enzymes. They function best at acidic pH
Primary lysosome
fuses with the endosomes to generate a secondary lysosome and digest the material inside
Lysosome involvement in endocytosis
used to digest the material brought into the cell by endocytosis, to render the material harmless and make the digested material usable to the cell
Structure of mitochondrial membranes
two membranes.
outer membrane covers the entire organelle
inner membrane is entirely folded
How did mitochondria arise as organelles
they were originally free-living bacteria that became incorporated into the cytoplasm of eukaryotic cells. They are self replicating
Chloroplasts were once
free-living bacteria
What organelles are unique to plants
plastids and vacuoles.
Most important plastid is the
chloroplast
Internal membrane structure of a chloroplast
three membranes,
outer membrane completely covers the organelle, inner membrane also completely covers the organelle. Chloroplasts have a third membrane
Chloroplasts have a third membrane, called the
thylakoid membrane is the site of photosynthesis
Different cytoskeletal elements
microfilaments, microtubules and intermediate filaments
Microfilaments
made of actin
long, thin fibers that support the cell, and in association with myosin, help the cell move
Microtubules
hollow tubes that also provide structural support, and help the cell move
responsible for moving objects, such as vesicles, around the cell.
form “railroad tracts” on which the motor proteins dynein and kinesis carry cargo one direction of dyenin and the other direction of myosin
Intermediate Filaments
composed of long strands made from fibrous protein subunits noncovalently bonded end to end
provide shape and structural support at various places in the cell
do NOT have role in movement
What kinds of proteins interact with cytoskeletal elements to create motion and movment?
motor proteins
Dynein and kinesin interact with
microtubules
Fibrous Connective Tissue
contains a large amount of extracellular matrix with relatively few cells
Example of Fibrous connective tissue
tendons and ligaments
Epithelial Cells
cells that form layers, often lining the internal cavities of the body, such as the intestines
separated from the rest of the body by a sheet of extracellular matrix called the basal lamina
Functions of Plasma Membrane
separates external from internal compartments
semipermeable barrier
has a very thin flexible covering
What makes the membrane a bilayer
the area of a monolayer of phospholipids from red blood cells is twice the area of the membrane in those cells
Phospholipids
consist of polar head groups and nonpolar fatty acid tails
in presence of water, they organize into bilayers
Membranes are selectively
permeable
A pure phospholipid membrane is somewhat permeable to
small polar molecules
A pure phospholipid membrane is very impermeable to
ions and other charged molecules
What is a model in science?
simpler description of a complex phenomenon
conceptual and analytic
What is the role of models in modern day science?
developing and testing them
what does it mean when a membrane is “fluid”
membrane maintains a barrier between what is inside and outside the cell
extends to proteins
Can the cell control the degree of fluidity in the membrane?
the chemical structure of fatty acids int eh membrane controls the degree of fluidity of the membrane
The cell can control the degree of fluidity by
changing the fatty acids of the phospholipids in the membrane
If the membrane has more unsaturated fatty acids, it will be
more fluid
if the membrane has more saturated fatty acids, then it will be
less fluid
Longer chain fatty acids will tend to make the membrane
less fluid
The shorter the chain fatty acids, will make the membrane
more fluid
How would a cell respond to an increase in temperature to maintain the same membrane fluidity?
the membrane would be more fluid, if too fluid, it will compensate to return the membrane to its original level of fluidity
cell would increase in the relative amount of saturated fatty acids and/or increase the length of the chains in the newly synthesized phospholipids, either of which decrease membrane fluidity
How would a cell respond to a decrease in temperature to maintain the same membrane fluidity?
less fluid membrane
if not fluid enough, will compensate
would increase the relative amount of unsaturated fatty acids and/or decrease the length of the chains in the newly synthesized phospholipids
If there is a higher concentration of a small hydrophobic molecule outside the cell than inside, what will happen?
the small hydrophobic molecule would enter the cell by simple diffusion
NO protein works with
intermediate filaments
anything that ends with “in” is a
protein
How can molecules that are permeable to the membrane move from a region of high concentration to a region of low concentration?
simple diffusion
what happens to molecules that are not permeable to the membrane?
facilitated diffusion
Facilitated diffusion proteins:
carrier proteins and channels
carrier protein
transports molecules one (or a few) at a time with each cycle of transport
channel proteins
allow many molecules to be transported at once
Facilitated diffusion and active transport can BOTH
transport molecules that are not permeable to a lipid bilayer across the membrane
A carrier must bind to a __________ _______ _______ before transport can occur
single molecule substrate
Channels allow the flow of molecules one after another through the channel is the analogy that they are like
bridges
Carriers for facilitated diffusion and transporters for active transport can both be classified into
uniporters, symporters, or antiporters
Uniporters
transport only a single molecular species in a single direction
Symporters and Antiporters
allow the transport of more than one species but differ in the directionallity of transport
Symporters carry
two species in the same direction
Antiporters carry two species in the
opposite direction
Osmosis
movement of water across a semipermeable barrier in response to a difference in concentration of solutes on either side of the membrane
When the solutes are impermeable to the membrane
water will follow the concentration gradient of free water, moving from regions of low solute concentration to high solute concentration
Isotonic Solutions
have the same concentration of solutes as a cell
cell is immersed in this solution, nothing will happen
Hypertonic Solution
greater concentration of solutes in a cell
water will move from inside the cell to outside causing it to shrivel and may die
Hypotonic Solution
those where the concentration of solutes is less than in a cell
if cell is placed in this solution, the concentration of solute is higher inside the cell. water will move into the cell and may cause it to BURST
parts of chromosome 1 that are being transcribed
are contained in the euchromatin
are contained in a different territory than chromosome 2
Germ line cells
eventually become sperm or egg
have to protect DNA for many generations
What molecule acts as a catalyst for formation peptide bonds?
ribosomal RNA (rRNA)
Note
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