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2.4 proteins Flashcards

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1
Q

what are proteins?

A
  • polymers made from amino acids which are
    the monomers
  • 20 amino acids that make up proteins found in cells
  • properties of proteins are determined by R group on the amino acids
  • structure:
    NH2 (amino group) CHR COOH (carboxyl group)
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2
Q

how are amino acids linked to form polypeptides?

A
  • by condensation reaction
  • OH in carboxyl group of 1 combines with H in amino group of another
  • bond combining the 2 amino acids is peptide bond
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3
Q

what are the 2 ends of a polypeptide called?

A

amino end: N-terminus

carboxyl end: C-terminus

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4
Q

why are there infinite possibilities of polypeptides?

A
  • could be any length
  • 20 amino acids
  • amino acids in any sequence, order or combination
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5
Q

where are polypeptides produced?

A
  • at the ribosomes in cells

- amino acids linked together in specific sequence as dictated by genes

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6
Q

what are genes?

A
  • sequences of DNA nucleotides carrying information for expression
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7
Q

how does dna become polypeptides?

A

dna -> (transcription) rna -> (translation) polypeptide

- dna strand is transcribed

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8
Q

what is the start codon?

A

AUG

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9
Q

what is the stop codon?

A

UAG

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10
Q

what are the 4 levels of protein structure that determine the final shape of the protein?

A
  • primary
  • secondary
  • tertiary
  • quaternary
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11
Q

what is the primary protein structure?

A
  • sequence of amino acids along the polypeptide chain

- determined from the genetic information stored in the cell

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12
Q

what is the secondary protein structure?

A
  • parts of the polypeptide chain can coil onto itself, leading to the formation of alpha helices
  • other parts of the polypeptide chain can fold itself in a beta pleated structure
  • hydrogen bonds between amino acid molecules stabilise these secondary structures
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13
Q

what is the tertiary protein structure?

A
  • overall three dimensional shape of a protein
  • usually arises from the interactions and bonds formed
    between R groups of amino acids within the protein
  • e.g disulphide bridge formed between two sulphur containing amino acids, leading to a strong bond formed
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14
Q

what is the quaternary protein structure?

A
  • when two or more polypeptide chains associate to form a resultant protein, this level of structure is the quaternary structure
  • not all proteins have a quaternary structure
  • collagen, which exists in a triple helix, is an example of a protein with a quaternary structure
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15
Q

can a protein consist of a single polypeptide? or must it always be more than 1 polypeptide linked together?

A

yes it can. multiple can be seen in quaternary structure but there are also proteins made of 1 single polypeptide.

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16
Q

what are the different functions of proteins?

A
  • enzymatic proteins
  • storage proteins (e.g. casein in milk as a storage for amino acids; egg albumin as a storage for amino acids)
  • hormonal proteins (insulin, glucagon, adrenaline, etc)
  • contractile and motor proteins (actin and myosin found in muscle cells)
  • defensive proteins (antibodies clumping onto bacteria)
  • transport proteins
  • receptor proteins
  • structural proteins

or SHITS ME

  • structure – e.g. collagen, spider silk
  • hormones – e.g. insulin, glucagon
  • immunity (defensive) – e.g. immunoglobulins
  • transport – e.g. haemoglobin
  • sensation (receptor)– e.g. rhodopsin
  • movement – e.g. actin, myosin
  • enzymes – e.g. Rubisco, catalase
17
Q

how do enzymatic proteins function?

A
  1. enzyme available w empty active site
  2. substrate binds to enzyme w induced fit
  3. substrate is converted to products
  4. products are released
18
Q

what is genome?

A

refers to the sum of all genes encoded within the DNA of that species

19
Q

what is proteome? and is it unique?

A
  • proteome refers to the sum of all proteins that can be produced by the species
  • dependent on the genome of the species, as well as the environment that affects which genes are expressed at that point in time
  • genome is unique for each species, likewise the proteome is also unique for each species
20
Q

what is rubisco?

A
  • ribulose bisphosphate carboxylase
  • enzyme used to fixed carbon dioxide from the atmosphere
  • provides a source of carbon during photosynthesis and formation of complex carbon compounds
  • found in high concentration in leaves of plants
21
Q

what is insulin?

A
  • hormone used to regulate blood glucose levels
  • secreted in response to high blood glucose levels, to stimulate cells to take in glucose
  • produced by the pancreas
22
Q

what are immunoglobulins?

A
  • also known as antibodies
  • total of 2 antigen binding sites per protein
  • rest of antibody is fixed, but different antibodies will have different antigen binding sites, leading to great specificity
  • can agglutinate bacteria, as antibodies can bind to antigens, and also bind to each other
  • agglutinated bacteria are not able to cause infections, and being clumped together makes the bacteria easier to be engulfed by white blood cells via phagocytosis
23
Q

what is rhodopsin?

A
  • pigment that can absorb light
  • also known as visual purple
  • found in receptor cells in the retina
  • when a photon reaches a rhodopsin molecule, isomerisation occurs leading to a change in shape of the molecule
    • sets off a chain of events that leads to the depolarisation of receptor cells and subsequently nerve cells
24
Q

what is collagen?

A
  • triple helix
  • structural protein, and about a quarter of all proteins
    found in the human body is collagen
  • forms a mesh in tissues, allowing for resistance against tearing and shearing
  • gives structural strength to tendons, ligaments, skin and blood vessels
25
Q

what is spider silk?

A
  • used to form webs by spiders
  • stronger than steel cables or Kevlar fibres if they all are of equivalent thickness
  • when stretched the fibres can extend, giving a greater resistance against breaking
26
Q

why do proteins denature at high heat or deviation of pH from optimum?

A
  • three dimensional shape of a protein is maintained by numerous internal bonds between amino acids in the protein
  • most of these bonds are relatively weak, and can be easily broken at higher temperatures
  • heat energy can increase the rate of vibration of atoms, and this vibration can break the weak internal bonds
  • extreme pH can change the charges of R groups on amino acids, breaking ionic bonds and hence leading changes in shape of the protein

sl bio (32 decks)

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