Protein Synthesis Summary
Protein Synthesis
1. The DNA double helix unwinds to expose a sequence of
nitrogenous bases. (A,T,C,G)
2. A copy of one of the strands is made in a process known as
transcription. The copy is made of messenger ribonucleic acid
(mRNA) which, following transcription, travels out of the nucleus
into the main body of the cell, where protein synthesis occurs.
3. The mRNA couples with the protein synthesis apparatus (the
ribosome). Another type of RNA, known as transfer RNA (tRNA),
brings free amino acids to the ribosome.
4. The anticodon present on the tRNA recognises the codon present
on the mRNA, and the ribosome adds the amino acid to the
growing chain of linked amino acids (polypeptides), cleaving it away
from the tRNA. This process is known as translation.
5. As the polypeptide chain grows, it folds to form a protein.
http://www.youtube.com/watch?v=983lhh20rGY
ENERGY RELATED ORGANELLES
Mitochondria - The Cell's Chemical Furnaces
• contains its own DNA, support for Endosymbiosis Theory
• singular is "mitochondrion“
• 2 membranes, one smooth outer membrane, and an inner
membrane folded into layers called cristae
• Cristae has two compartments: the matrix and the inter
membrane space
• function to store energy for cell
use. Energy is stored in the form of
ATP - adenosine triphosphate
• (Made by cellular respiration…
which we will learn later!)
Figure 4.17
Chloroplasts - Where Photosynthesis Takes Place
• only found in plant cells
• has its own DNA, like
mitochondrion
• functions to convert light
energy to carbohydrates
• carbohydrates then broken
down in mitochondria to
produce ATP
• consists of grana, closed compartments that are stacked
• thylakoids are the individual disk shaped compartments that make up the
grana (stack of thylakoids)
• stroma is the fluid surrounded the thylakoids
*Chloroplasts are a type of plastid
Chromoplasts – red, yellow and orange pigment
Leucoplasts – colorless (potatoes)
Endomembrane System
• Many of the different membranes of the eukaryotic cell are
part of this system which carry out a variety of tasks in the
cell. i.e. synthesis of proteins, metabolism and movement of
lipids, & detoxification of drugs and poisons
• The membranes of this system are related either through
physical continuity or by the transfer of membrane segments
as tiny vesicles (sacs made of membrane)
• This system includes: nuclear envelope, the endoplasmic
reticulum, golgi apparatus, lysosomes, various vacuoles, and
the plasma membrane
Endomembrane System
Endoplasmic Reticulum
• Extensive network accounting for more than half the
total membrane in eukaryotic cells
• Consists of a network of membranous tubules and
sacs called cisternae
• The ER membrane separates the internal
compartment of the ER, called the ER lumen (cavity)
or cisternal space, from the cytosol.
• The ER membrane is continuous with the nuclear
membrane
ER cont…
Two types of ER: smooth and rough
1. Smooth ER – lacks ribosomes and involved in
diverse metabolic processes such as lipid
synthesis, metabolism of carbohydrates,
and detoxification of drugs and poisons
2. Rough ER – has ribosomes and is involved in
protein synthesis
Figure 4.10a
Golgi Apparatus -- Delivery System
• flattened stacks of
membranes
• functions in collection,
packaging and
distribution of
molecules made in the
cell and used
elsewhere
• front end (cis) faces the
ER, and the back end
(trans) faces the cell
membrane
* folded stacks are called cisternae
• unprocessed proteins
enter the Golgi
apparatus from ER and
proteins are packaged
and exported to the
nearest membrane
Jobs of the Golgi Apparatus
(aka Golgi Complex)
1. separates proteins according
to their destinations
2. modifies proteins (adds sugar
and makes glycoproteins)
3. packages materials into
vesicles which are exported
outside the cell - secretion
Summary of Endomembrane System
See Handout*
Lysosomes - Intracellular Digestion Centers
• vesicles that are used to digest
• contain high levels of degrading
enzymes – low pH
(to "lyse" means to dissolve)
• recycle old and worn out cell parts
• "suicide sac" - apoptosis (wikipost
HWK)
• digest other particles taken in by
phagocytosis
http://www.youtube.com/watch?v=m
6qJ69wcSnc
• found in animal cells
TAY-SACHS disease – missing an
enzyme of the lysosomes that breaks
down a fatty substance. Over time this
fat builds up in the brain and nervous
tissue, smothering the cells. Results in
degeneration and death.
Vacuoles
Types:
1. Food vacuoles – formed by phagocytosis
http://www.youtube.com/watch?v=W6rnhiMxtKU
2. Contractile vaculoes – pump excess water out of
the cell
http://www.youtube.com/watch?v=kkPiRT2ewVA
3. In plants & Fungi – Central vacuole: stores food,
nutrients, water and waste…maintains turgor
pressure (prefer a hypotonic state)
Mini Quiz
1. What part of the cell
produces vesicles for export?
2. What part of the cell makes
proteins?
3. What part of the cell
produces ATP?
4. What part of the cell
transports materials
throughout the cytoplasm?
5. What part of the cell has a
cis and a trans face?
a. ________________
b. ________________
c. _________________
d. _________________
e. _________________
f. __________________
f.
What is this structure?
Figure 4.7b
Figure 4.10a
What is this structure?
What is this
structure?
Figure 4.11
Describe the
processes occurring in
this image.
Figure 4.13
Figure 4.16b
What is this structure?
What is this structure?
What is its function?
Find the:
a. Nucleolus
b. Centriole
c. Vesicle
d. Smooth ER
e. Lysosome
Summary Video Clip
http://www.youtube.com/watch?v=3jWV568GpkU