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1.2 Flashcards

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1
Q

What are prokaryotes?

A

Unicellular organisms that lack nuclear membrane

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2
Q

Example of a prokaryote..

A

A bacterial cell

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3
Q

What are eukaryotes?

A

Can be unicellular or multicellular organisms that have genetic material contained inside membrane bound nucleus.

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4
Q

Examples of a eukaryote…

A

Animals; plants; protists (amoeba, paramecium); fungi.

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5
Q

What is the proteome?

A

The entire set of proteins expressed by a genome, larger than the genome due to RNA splicing.

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6
Q

Why are not all genes expressed as proteins?

A

Some are non-coding RNa genes, including those that transcribe to produce tRNA, rRNA and RNA molecules that control other gene expression.

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7
Q

Examples of gene expression factors…

A

cell metabolic activity; cellular stress; response to signalling molecules; diseased vs. healthy cells.

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8
Q

How do eukaryotes increase membrane surface area?

A

As the plasma membrane is too small to carry out vital membrane functions, internal membranes are used to increase the total membrane are.

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9
Q

What is the endoplasmic reticulum (ER)?

A

a network of membrane tubules continuous with the nuclear membrane.

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10
Q

What are the two types of ER?

A

Rough ER (RER) has ribosomes on its cytosolic face.
Smooth ER (SER) lacks ribosomes, it produces phospholipids and membrane proteins and inserts them into membrane.

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11
Q

Where do transmembrane proteins finish getting translated?

A

In the ER.
They carry a signal sequence which halts translation and directs the synthesising ribosome to dock with the ER to the RER and translation continues after docking.

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12
Q

What is a signal sequence?

A

A short amino acid stretch at one end of the polypeptide that determines eventual cell location of protein.

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13
Q

What is the golgi apparatus?

A

A series of flattened membrane discs

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14
Q

What are lysosomes?

A

Membrane bound organelles containing a variety of hydrolases that digest proteins, lipids, nucleic acids and carbohydrates.

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15
Q

What are vesicles used for?

A

Used to transport materials between membrane compartments.

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16
Q

What happens to transmembrane proteins once translated in the ER?

A

They are transported by vesicles that fuse to the golgi apparatus. Molecules move through discs by vesicles and proteins go through post-translational modification (PTM) here.

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17
Q

What is a PTM example?

A

A major modification is the addition of carbohydrate groups.
Enzymes catalyse the addition of various sugars in multiple steps to form carbohydrates.

18
Q

How do membrane proteins get to the plasma membrane?

A

Vesicles leave the golgi apparatus by moving along microtubules to fuse with membranes.

19
Q

What is the secretory pathway?

A

Secreted proteins enter the ER lumen, proteins then move through the golgi and are packaged in secretory vesicles which fuse with the PM and releases proteins out of the cell.

20
Q

Examples of secreted proteins…

A

Peptide hormones like insulin and digestive enzymes.

21
Q

What is proteolytic cleavage?

A

Type of PTM.
Some secreted proteins synthesised as inactive precursors and need this to produce active proteins, breaks peptide bonds between amino acids, carried out by protease enzymes.

22
Q

What determines protein structure?

A

Amino acid sequence

23
Q

What are the 4 types of amino acids? (PHAB)

A

Polar - R groups contain OH groups (hydroxyl)
Hydrophobic - R groups are hydrocarbons, benzene rings and/or non-polar.
Acidic - negatively charged R groups (e.g. COO⁻)
Basic - positively charged R groups (e.g. NH₂, NH₃)

24
Q

What is the primary structure of a protein?

A

Polypeptide chain.
Proteins are polymers of amino acid monomers which are linked by peptide bonds.

25
Q

What is the secondary structure of a protein?

A

When hydrogen bonds form along the protein strand backbone.

26
Q

Examples of secondary structure…

A

Alpha helix, Beta-pleated sheets (usually anti-parallel but can be parallel), turns.

27
Q

What stabilises the tertiary structure of a protein?

A

Stabilised by different R group interactions such as hydrophobic interactions, ionic bonds, LDF’s and disulfide bridges (covalent bond between 2 thiol (S-H) groups).

28
Q

What are prosthetic groups?

A

non-protein unit tightly bound to a protein, necessary for its function.

29
Q

Example of a prosthetic group…

A

Haem group in haemoglobin contains iron atom to allow oxygen to bond.

30
Q

What is quaternary structure?

A

When a protein has 2+ connected polypeptide units.

31
Q

What is cooperativity in a protein?

A

Where binding change on one subunit alters the affinity of remaining subunits.

32
Q

How does pH and temperature affect R group interactions?

A

Incr. temperature disrupts interactions and leads to denaturing.
Charged on acidic and basic R groups are affected by pH, causes ionic interactions to be lost and protein to change conformation.

33
Q

Effects of pH and temperature on haemoglobin…

A

changes in oxygen binding at one subunit alters affinity at other subunits.
Decr. in pH or Incs. in temperature lowers oxygen affinity so oxygen binding is reduced.
When this occurs in respiring tissue, oxygen binding is reduced which helps to deliver oxygen.
Carbon dioxide is an acidic gas which helps to lower pH.

34
Q

What are ligands?

A

Substances that can bind to a protein and change it’s conformation. The conformational change causes a functional change in the protein.

35
Q

How do ligands bind to proteins?

A

R-groups not involved in folding allow ligand binding, binding sites have complementary shape and chemistry to the ligand.

36
Q

Non-competitive inhibitors…

A

doesn’t bind to active site; binds to allosteric site and changes enzyme shape, indirectly affecting the active site.

37
Q

Allosteric enzymes…

A

Allosteric interactions occur between spatially distinct sites; consist of multiple subunits and show cooperativity in binding.

38
Q

What does a modulator do?

A

regulate enzyme activity when they bind to the allosteric site.

39
Q

What do positive modulators do?

A

they increase enzyme affinity whereas negative modulators reduce enzyme activity.

40
Q

Protein phosphorylation …

A

Is a form of PTM; the addition of removal of a phosphate can cause a reversible conformational change of proteins as adding a phosphate adds a negative charge and disrupts ionic interactions.

41
Q

What do protein kinases do?

A

catalyse the transfer of phosphate group to other proteins; phosphorylation

42
Q

What do protein phosphatases do?

A

catalyse dephosphorylation

advanced higher biology (17 decks)

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