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IB Bio > 2.4 > Flashcards

2.4 Flashcards

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Biology 101 flashcards
1
Q

Proteins are comprised of long chains of recurring monomers called

A

amino acids

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2
Q

Amino acids all share a common basic structure, with a central carbon atom bound to:

A
  • An amine group (NH2)
  • A carboxylic acid group (COOH)
  • A hydrogen atom (H)
  • A variable side chain (R)
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3
Q

how many different amino acids are there?

A

There are 20 different amino acids which are universal to all living organisms

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4
Q

Amino acids are joined together on the ribosome to form long chains called…

A

polypeptides, which make up proteins

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5
Q

amino acid side chains

A

Each type of amino acid differs in the composition of the variable side chain

These side chains will have distinct chemical properties (e.g. charged, non-polar, etc.) and hence cause the protein to fold and function differently according to its specific position within the polypeptide chain

As most natural polypeptide chains contain between 50 – 2000 amino acid residues, organisms are capable of producing a huge range of possible polypeptides

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6
Q

Amino acids can be covalently joined together in what type of reaction?

A

condensation reaction

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7
Q

polypeptides are…

A

The covalent bond between the amino acids is called a peptide bond and, for this reason, long chains of covalently bonded amino acids

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8
Q

Polypeptide chains can be broken down via what type of reaction?

A

hydrolysis reactions

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9
Q

amino acid condensation reactions form…

A

a dipeptide and water

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10
Q

polypeptide hydrolysis reactions require…

A

water to reverse the process

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11
Q

peptide bonds are formed between

A

the amine and carboxylic acid groups of adjacent amino acids

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12
Q

peptide bonds cause the…

A

the amine group to lose a hydrogen atom (H) and the carboxylic acid loses a hydroxyl (OH) – this forms water (H2O)

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13
Q

Amino acids are covalently joined via peptide bonds to form…

A

polypeptides

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14
Q

the primary structure of amino acids is…

A

the order of the amino acid sequence

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15
Q

the primary structure of an amino acid sequence determines the…

A

the way the chain will fold
- Different amino acid sequences will fold into different configurations due to the chemical properties of the variable side chains

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16
Q

the secondary structure of amino acids refers to

A

Amino acid sequences will commonly fold into two stable configurations

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17
Q

types of amino acid secondary structure

A

Alpha helices and beta-pleated sheets

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18
Q

alpha helices

A

occur when the amino acid sequence folds into a coil / spiral arrangement

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19
Q

beta-pleated sheets

A

occur when the amino acid sequence adopts a directionally-oriented staggered strand conformation

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20
Q

both α-helices and β-pleated sheets result from what type of bonds?

A

hydrogen bonds forming between non-adjacent amine and carboxyl groups

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21
Q

what happens when no secondary structure exists?

A

the polypeptide chain will form a random coil

22
Q

the tertiary structure of the protein is the

A

The overall three-dimensional configuration of the protein

23
Q

The tertiary structure of a polypeptide chain will be determined by

A

the interactions between the variable side chains

24
Q

interactions between variable side chains may include

A

hydrogen bonds, disulphide bridges, ionic interactions, polar associations, etc.

25
Q

the overall shape of the polypeptide chain is affected by

A

The affinity or repulsion of side chains and are determined by the position of specific amino acids within a sequence

26
Q

what determines all subsequent levels of protein folding?

A

The order of the amino acid sequence (primary structure) determines all subsequent levels of protein folding

27
Q

quaternary structure

A

certain proteins possess a fourth level of structural organisation

28
Q

Quaternary structures are found in proteins that consist of?

A

more than one polypeptide chain linked together and can also be found if they include inorganic prosthetic groups as part of their structure

29
Q

example of a protein with a quaternary structure

A

haemoglobin (O2 carrying molecule in red blood cells)

30
Q

haemoglobin

A
  • Haemoglobin is composed of four polypeptide chains (two alpha chains and two beta chains)
  • It is also composed of iron-containing haeme groups (prosthetic groups responsible for binding oxygen)
31
Q

Denaturation

A

is a structural change in a protein that results in the loss (usually permanent) of its biological properties

Because the way a protein folds determines its function, any change or abrogation of the tertiary structure will alter its activity

32
Q

Denaturation of proteins can usually be caused by two key conditions

A

temperature and pH

33
Q

Temperature denaturation

A
  • High levels of thermal energy may disrupt the hydrogen bonds that hold the protein together
  • As these bonds are broken, the protein will begin to unfold and lose its capacity to function as intended
  • Temperatures at which proteins denature may vary, but most human proteins function optimally at body temperature (~37ºC)
34
Q

pH

A
  • Amino acids are neutral molecules possessing both negatively and positively charged regions
  • Changing the pH will alter the charge of the protein, which in turn will alter protein solubility and overall shape
  • All proteins have an optimal pH which is dependent on the environment in which it functions (e.g. stomach proteins require an acidic environment to operate, whereas blood proteins function best at a neutral pH)
35
Q

gene

A

A gene is a sequence of DNA which encodes a polypeptide sequence

36
Q

a gene sequence is converted into a polypeptide sequence via two processes:

A
  • Transcription – making an mRNA transcript based on a DNA template (occurs within the nucleus)
  • Translation – using the instructions of the mRNA transcript to link amino acids together (occurs at the ribosome)
37
Q

Typically, one gene will code for one polypeptide – however there are exceptions to this rule (3):

A
  • Genes may be alternatively spliced to generate multiple polypeptide variants
  • Genes encoding tRNA sequences are transcribed but never translated
  • Genes may be mutated (their base sequence is changed) and consequently produce an alternative polypeptide sequence
38
Q

proteome

A

The proteome is the totality of proteins expressed within a cell, tissue or organism at a certain time
- The proteome of any given individual will be unique, as protein expression patterns are determined by an individual’s genes

39
Q

The proteome is always significantly larger than the number of genes in an individual due to a number of factors:

A
  • Gene sequences may be alternatively spliced following transcription to generate multiple protein variants from a single gene
  • Proteins may be modified (e.g. glycosylated, phosphorylated, etc.) following translation to promote further variations
40
Q

Proteins are a very diverse class of compounds and may serve a number of different roles within a cell, including:

A

SHITS ME

41
Q

SHITS ME

A 
Structure – e.g. collagen, spider silk
Hormones – e.g. insulin, glucagon
Immunity – e.g. immunoglobulins
Transport – e.g. haemoglobin
Sensation – e.g. rhodopsin
Movement – e.g. actin, myosin
Enzymes – e.g. Rubisco, catalase
42
Q

Structure

A

Collagen: A component of the connective tissue of animals (most abundant protein in mammals)
Spider silk: A fiber spun by spiders and used to make webs (by weight, is stronger than kevlar and steel)

43
Q

Hormones

A

Insulin: Protein produced by the pancreas and triggers a reduction in blood glucose levels
Glucagon: Protein produced by the pancreas that triggers an increase in blood glucose levels

44
Q

Immunity

A

Immunoglobulins: Antibodies produced by plasma cells that are capable of targeting specific antigens

45
Q

Transport

A

Haemoglobin: A protein found in red blood cells that is responsible for the transport of oxygen
Cytochrome: A group of proteins located in the mitochondria and involved in the electron transport chain

46
Q

Sensation

A

Rhodopsin: A pigment in the photoreceptor cells of the retina that is responsible for the detection of light

47
Q

Movement

A

Actin: Thin filaments involved in the contraction of muscle fibres
Myosin: Thick filaments involved in the contraction of muscle fibres

48
Q

Enzymes

A

Rubisco: An enzyme involved in the light independent stage of photosynthesis

49
Q

There are two main classes of protein tertiary structure:

A

fibrous and globular

50
Q

Fibrous proteins

A

Fibrous proteins are generally composed of long and narrow strands and have a structural role (they are something)

51
Q

Globular proteins

A

Globular proteins generally have a more compact and rounded shape and have functional roles (they do something)

IB Bio (18 decks)

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