BIOLOGY 1A03 Lecture 3: Theme 1 Module 3 (pdf)
27 Jun 2018
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Module 1 – The Structure of cell. Module 3 – Proteins
Unit 1 – Proteins: What do they do, how are they made and what do they look like?
Proteins have various features
Transport and signally
Movement and structure
Enzymes
Defense – B-cells of the immune system produce antibodies (made up of proteins)
Proteins have various structures
TATA-box binding protein, which interacts with DNA molecules, is able to do so due to a
groove in the protein that allows for this interaction.
Porin proteins are important for transport of water for example across the cell membrane and
have a structural hydrophilic pore that allows for this to occur.
Most soluble cellular proteins may take more globular shapes with a hydrophobic interior and a
hydrophilic exterior that allows the protein to be soluble in the aqueous environment of the
cytosol, such as hemoglobin at the bottom.
How are protein structures represented?
Space filling diagram – shows actual relative size and location of each atom, representing
atoms with different colors
Ribbon diagram – the liens represent the backbone of the protein polymer. The broader line
represents an organized reiterated structure called an alpha helix while the thinner line
represents a less ordered loop
Unit 2 – An overview of protein synthesis : from DNA to Primary Protein Structures
Genetic information codes for proteins
The basic principles are the same for both prokaryotic and
eukaryotic cells.
The genetic information for every protein is encoded in the DNA of
the cell.
The first step is to transcribe that information into RNA which
serves as the template for synthesis of a polypeptide.
In the prokaryotic cell this is closely linked with translation of the
RNA into proteins by ribosomes.
In a eukaryotic cell the primary RNA transcript is processed to messenger or mRNA and
transported into the cytoplasm where it is then translated into the protein by the ribosomes.
The code for a protein sequence is in the nucleus
The nucleus is a double membrane bound domain that contains
chromosomes which pack and control DNA molecules
This information in a gene (DNA) is transcribed into a copy (mRNA)
Nuclear pores connect nucleus with the cytosol
The double membrane of the nuclear envelope has embedded nuclear
pore complexes that allows for material to flow into and out of the nucleus.
Most ribosomal RNAs are manufactured in the nucleolus where they bind to proteins to form
the ribosomal subunits.
These structures are then exported to the
cytoplasm.
Allow the transcribed RNA to exit the nucleus for
further processing in the extranuclear regions
mRNA which has been transcribed from DNA and
carries the information to make proteins are also
transported to the cytoplasm through these nuclear
pores.
They can also import the important building blocks of DNA and RNA into the nucleus, along
with enzymes that are important for the transcription of DNA into RNA.
Ribosomes synthesize proteins
The structural components of ribosomes are made in the nucleolus and are then shipped out
of the nucleus.
Once exported from the nucleus, these ribosomes assemble and have large and small subunit
components that both contain RNA molecules and proteins.
Ribosomes are able to remain soluble in the cytoplasm as free ribosomes or can attach to the
endoplasmic reticulum to become bound ribosomes.
These two different types of ribosomes can produce different proteins that will be destined for
different parts of the cell or even secretion.
All proteins are linear polymers of amino acids
Condensation reactions polymerize amino acids, releasing water
Hydrolysis breaks these polymers apart by adding water molecules
Amino acids have a common structure: a central carbon atom bound to an amino group, a
carboxyl group, a hydrogen atom and a variable side chain (represented by the R).
Amino acid monomers are put together to make linear strands which we call polymers or
polypeptides.
A polypeptide is a strand of amino acids that are covalently bound to one another through a
condensation reaction which releases water.
During protein synthesis, the unique sequence of amino acids in each protein is referred to as
the primary structure of that protein.
Translation occurs inside the ribosome
Condensation happens in ribosome
1) The ribosome binds to mRNA at a specific area.
2) The ribosome starts matching tRNA anticodon
sequences to the mRNA codon sequence.
3) Each time a new tRNA comes into the ribosome, the
amino acid that it was carrying gets added to the
elongating polypeptide chain.
4) The ribosome continues until it hits a stop sequence,
then it releases the polypeptide and the mRNA.
5) The polypeptide forms into its native shape and starts
acting as a functional protein in the cell.
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BIOLOGY 1A03 Full Course Notes
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Document Summary
Defense b-cells of the immune system produce antibodies (made up of proteins) Tata-box binding protein, which interacts with dna molecules, is able to do so due to a groove in the protein that allows for this interaction. Porin proteins are important for transport of water for example across the cell membrane and have a structural hydrophilic pore that allows for this to occur. Most soluble cellular proteins may take more globular shapes with a hydrophobic interior and a hydrophilic exterior that allows the protein to be soluble in the aqueous environment of the cytosol, such as hemoglobin at the bottom. Space filling diagram shows actual relative size and location of each atom, representing atoms with different colors. Ribbon diagram the liens represent the backbone of the protein polymer. The broader line represents an organized reiterated structure called an alpha helix while the thinner line represents a less ordered loop.
