1.2 - Proteins Flashcards
What is the proteome?
The proteome is the entire set of proteins expressed by a genome.
What factors affect the set of protein expressed by a given cell type?
The metabolic activity of the cell
State of cellular stress
Response to signalling molecules
State of health/disease and/or during apopotosis
How can more than one protein be expressed from a single gene?
Alternative RNA splicing
What is cystol?
Cytoplasm
What are genes that do not code for proteins called?
Non-coding RNA genes
Do eukaryotic cells have a small surface area to volume ratio?
Yes
What is the Golgi apparatus?
A series of flattened membrane discs
What are vesicles?
They transport materials between membrane compartments.
What are lysosomes?
Lysosomes are membrane bound organelles containing a wide variety of hydrolases.
What are lysosomes?
Lysosomes are membrane bound organelles containing a wide variety of hydrolases.
What do the hydrolases in lysosomes do?
Digest: proteins Lipids Nucleic acids Carbohydrates
What factor affect the set of proteins expressed by a given cell type are?
The metabolic activity of the cell State of cellular stress Response to signalling molecules State of health Disease Apoptosis
Are all genes expressed as proteins in a particular cell?
Not all genes are expressed as proteins in a particular cell,
And the set of proteins expressed by a given cell type can vary over time
And under different conditions.
What are genes that don’t code for proteins called?
Non-coding RNA genes
What do non coding RNA genes do?
some are transcribed to produce tRNA, rRNA and various other RNA molecules that control the expression of protein-encoding genes
Do eukaryotic cells have a relatively small surface area to volume ratio?
Yes
What is the surface area of eukaryotic cells membranes too small to carry out?
All the vital functions that rely on membranes and the specialised proteins associated with them.
How do eukaryotic cells increase their total membrane area?
They have an internal system of specialised membranes called the endoplasmic reticulum (ER) which forms a network of membrane tubules continuous with the nuclear membrane.
What does ER stand for?
Endoplasmic reticulum
What does RER stand for?
Rough endoplasmic reticulum
What does SER stand for?
Smooth Endoplasmic Reticulum
Does the RER have ribosomes?
RER has docked ribosomes on its cytosolic face
Does SER have ribosomes?
SER lacks riobosomes
What is the Golgi apparatus?
The Golgi apparatus is a series of flattened membrane discs related to the ER and has associated vesicles that transport materials between membrane compartments.
What are lysosomes?
Lysosomes are formed from specialised Golgi vesicles.
Lysosomes are membrane bound organelles containing a variety of hydrolases that can digest proteins, lipids, nucleic acids and carbohydrates.
What are the main membrane components?
Phospholipids and proteins are the main membrane components.
Describe phospholipid molecules in the cell membrane
Phospholipid molecules have a hydrophilic head and hydrophobic tails.
They are formed into a bilayer.
Where are lipids synthesised?
The SER
Where does the synthesis of all proteins begin?
In cytosolic ribosomes
Where is the synthesis of cytosolic proteins completed?
In cytosolic ribosomes
Where do cytosolic proteins remain?
These proteins remain in the cytsol of the cell where they carry out their specific functions.
What is cytosol another word for?
Cytoplasm
What is cytoplasm another word for?
Cytosol
Where is the synthesis of transmembrane proteins completed?
The synthesis of transmembrane proteins begins in cytosolic ribosomes but is completed when the relevant cytosolic ribosomes dock with the ER to become part of the RER.
Where are transmembrane proteins permanently attached?
Transmembrane proteins are integral to the membrane and are permanently attached there.
Are all internal proteins completely transmembrane?
No
What do transmembrane proteins carry?
A signal sequence
What is a signal sequence?
A short stretch of 16-30 amino acids at one end of a polypeptide that will determine the eventual location of that protein in a cell.
What is proteolytic cleavage?
Proteolytic cleavage is a type of post-traditional modification.
What is an example of an intracellular protein?
Enzymes that control glycolysis.
What is an example of a transmembrane protein?
Channel proteins to permit the transport of specific substances across the cell membrane
What is an example of extracellular protein for secretion?
Peptide hormones such as insulin, enzymes such as salivary amylase and hydrolases that enter lysosomes.
Describe what is meant by the proteome
The entire set of genes expressed by the genome
Explain why the proteome is larger than the genome in many eukaryotic organisms
An individual gene may be expressed to produce several different proteins because of alternative splicing
Describe alternative RNA splicing
During splicing different Exons may be retained
Different introns may be removed
List three factors that can affect the set of proteins expressed by a cell type
Metabolic activity, which changes with age/senescence/dormancy state
Cellular stress level, which depends on extremes of temperature/pH/ exposure to toxins/ mechanical damage
Response to signalling molecules such as hormones/antigens exposure
State of health
Apoptosis
Describe the various different membranes inside a cell
Endoplasmic reticulum (ER) is a system of membrane tubules,
Continuous with nuclear membrane,
Can be rough (RER) with ribosomes,
Or smooth (SER) without ribosomes,
Golgi apparatus is related to ER,
Forms vesicles/involved in the formation of lysosomes
Name the chemical components of a cell membrane and their synthesis
Phospholipids synthesised in SER
transmembrane proteins started in cytosolic ribosomes and Finished in docked ribosomes/RER
Describe the differences between the various protein synthesised in cells in terms of their final destinations
Cytosolic proteins are synthesised in cytosolic ribosomes
Transmembrane proteins start in cytosolic ribosomes and finish in docked ribosomes/RER and are inserted into ER membrane
Secretory protein started in cytosolic ribosomes and finished in docked ribosomes and released into ER lumen
Describe two different types of post translational modification
Addition of carbohydrate in Golgi apparatus
Proteolytic cleavage of digestive enzymes in gut
Name the 4 types of R group and describe the characteristics of each
Hydrophobic - uncharged
Basic - positively charged/hydrophilic
Acidic - negatively charged/hydrophilic
Polar - small balanced charges/ have no net charge
Describe the primary and secondary level of protein structure
Primary is a sequence of amino acids
Secondary is folding to produce helixes/sheets/turns, held in shape by hydrogen bonds
Name 5 types of bond that can hold the tertiary structure of protein in shape
Hydrophobic attractions Ionic bonds Covalent disulfide bridges London dispersion forces Hydrogen bonds
Describe the quaternary structure of a protein
Arrangement of subunits
May have prosthetic groups
Explain what is meant by co-operativity between subunits of a protein
Binding or disbanding of substances at subunits
Affects affinity of these substances for further subunits
Describe co-operativity in haemoglobin
Binding of oxygen to first subunit
Increases affinity of further subunits for oxygen
Describe allosteric sites and how modulators affect enzyme action
Allosteric sites are binding sites but not the active site
Positive modulators increase activity at binding site/are activators
Negative modulators decrease activity at active site/are inhibitors
Explain how phosphorylation can affect the functioning of proteins
Phosphorylation is by kinases/changes conformation of protein can activate protein
De-phosphorylation is by phosphates/changes conformation of protein and can deactivate protein
Describe the location (s) of translation of the enzymes that are to be secreted from the cell
Starts in cytosolic ribosomes
Finished in docked ribosomes/ribosomes on ER
Describe one example of a post transitional modification that might occur within the Golgi apparatus
Addition of carbohydrate
Describe how enzymes within vesicles leaving the Golgi apparatus are secreted
Vesicles fuse with cell membrane and contents are released
Give one post translation modification to an enzyme that happens following secretion
Proteolytic cleavage
Give the term used to describe non-protein groups, such as harm, which are tightly bound to proteins and are essential for their function
Prosthetic group
Name two substances produced by a rapidly respiring muscle cell which would reduce its pH
Carbon dioxide
Lactate/lactic acid
