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Alevel biology > Water & Proteins > Flashcards

Water & Proteins Flashcards

1
Q

what is a covalent bond?

A

the sharing of a pair of electrons between two atoms
occurs between nonmetals
atoms want to try and get a full outer shell
eg - H2O,NH3, Cl2

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2
Q

what type of molecule is water and why?

A

polar molecule
uneven distribution of electrons (charge)
oxygen attracts the pair of electrons in the OH bond stronger than hydrogen
oxygen becomes delta negative, hydrogen becomes delta positive

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3
Q

what are hydrogen bonds?

A

weak electrostatic interactions when molecules contain a delta negative charge atom bonded to a delta positive charged hydrogen atom
weaker than a covalent bond but lots of them can stabilise structures

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4
Q

what is a metabolism?

A

all biochemical reactions happening inside of the cells of an organism
molecules that are eaten become part of the body or used to provide energy to drive metabolism
eg - carbohydrates, lipids, proteins

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5
Q

what are catabolic reactions?

A

breaking down large molecules - hydrolysis reactions (digestion)

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6
Q

what are anabolic reactions?

A

building large molecules - condensation reactions (protein synthesis)

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7
Q

what is a cell made up of?

A

30% chemicals - DNA, phospholipids, polysaccharides, ions, RNA, 15% proteins
70% water

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8
Q

what are carbohydrates?

A

for energy storage & supply
for structure (plant cellulose cell wall)
monomer = monosaccharides (glucose, fructose, galactose)
polymer = polysaccharides (starch, cellulose, glycogen)

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9
Q

what are proteins?

A

for structure (keratin in hair, collagen in skin)
for transport (channel & carrier)
enzymes, antibodies, most hormones
monomer = amino acids (glycine, tyrosine)
polymer = polypeptides (haemoglobin)

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10
Q

what is the function of lipids?

A

plasma membranes
energy storage and supply
insulation of animals
nerve cell insulation
steroid hormones

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11
Q

what is the function of vitamins and minerals?

A

form parts of larger molecules
vitamins = co-enzymes
minerals= inorganic cofactors for enzymes

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12
Q

what are nucleic acids?

A

contain genes that code the amino acid sequence of proteins
monomer = nucleotides
polymer = polynucleotides (DNA, RNA)

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13
Q

what is the function of water?

A

supports plants
solvent for metabolic reactions
transport medium

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14
Q

which biological molecules contain carbon, hydrogen & oxygen?

A

carbohydrates, proteins, lipids & nucleic acids

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15
Q

what are monomers?

A

single molecular units repeated to make polymers

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16
Q

what are polymers?

A

large molecules made from joining monomers of the same type together

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17
Q

what is hydrolysis?

A

a water molecule is used
a covalent bond breaks
monomer molecules form polymer
normally need an enzyme
eg - digestion

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18
Q

what is condensation?

A

a water molecule is released
a covalent bond forms
polymer molecules form monomers
normally need an enzyme
eg - transcription, translation & DNA replication

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19
Q

why is it important that water is a liquid?

A

hydrogen bonds form between the water molecules forming a network that allows them to move around, continually making and breaking hydrogen bonds
used as a liquid transport medium moving materials around living organisms
eg - in vascular tissues (xylem & phloem) and blood

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20
Q

why is it important that water is a good solvent?

A

polar molecules dissolve in water (nitrate ions) & organisms can take these in
water is attracted to the ions around them and separates them
medium for metabolic reactions
most of the cytoplasm is water with dissolved chemicals respiration and photosynthesis relies on this 

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21
Q

why is cohesion important in water?

A

hydrogen bonds between water molecules results in them sticking to each other
long, thin columns of water are very strong and difficult to break (xylem - transpiration)
create surface tension at the water surface - used by small invertebrates (pond skaters) to walk on water providing a habitat

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22
Q

why is the density of water when frozen important?

A

when water cools to become ice, its density decreases
the molecules spread out more due to more & longer hydrogen bonds forming between H2O molecules, creating an open lattice structure
ice floats on water creating habitats (for polar bears)
ice insulates water below so aquatic organisms do not freeze and can swim

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23
Q

why is a high specific heat capacity important in water?

A

a relatively large amount of energy is needed to raise the temperature of water as there are many stable hydrogen bonds between water molecules that need to be broken
the temperature of large bodies of water remain stable - good for aquatic organisms
prevents internal temperature inside organisms changing quickly so enzymes can function correctly

24
Q

why is high latent heat of vaporisation important in water?

A

evaporation of water uses up a relatively large amount of energy as there are many stable hydrogen bonds between water molecules that need to be broken
organisms use evaporation of water as an efficient cooling mechanism (panting & sweating)

25
why is metabolism important in water?
water takes part as a reactant in chemical processes inside cells water used in photosynthesis water molecules used in hydrolysis reactions
26
how many different amino acids and R-groups are there?
20
27
what is the structure of an amino acid?
amino group carboxyl group R-group (different in every amino acid)  central carbon atom hydrogen atom
28
how many amino acids do you need and make?
make = 12 need = 8 (essential)
29
what are the two types of R-group?
polar - hydrophilic (charged) nonpolar - hydrophobic
30
why is cysteine important?
in keratin found in hair & nails
31
what are the types of amino acids?
dipeptide = 2 tripeptide = 3 polypeptide = > 3
32
how is a dipeptide formed?
condensation reaction (water is made) a peptide bond is formed - C & N atoms bond the OH group of the carboxyl group of one amino acid bonds with the H atom of the amino group of another amino acid to form H2O
33
how is a dipeptide broken down?
hydrolysis reaction (water is used up) a peptide bond is broken - C to N bond the OH group of H2O joins to the C of the peptide bond to reform the carboxyl group the H atom left over from H2O bonds to the N of the peptide bond to reform the amino group amino acids are made from the dipeptide 
34
what are the four levels of protein structure?
primary structure secondary structure tertiary structure quaternary structure
35
what is the primary structure of a protein?
the specific sequence of amino acids in the protein chain  amino acids are connected by peptide bonds (the number of them is always 1 less than the number of amino acids) determines what the tertiary structure will be
36
what is the secondary structure of the protein?
the coiling of parts of the polypeptide chain to form an alpha helix the pleating of parts of the polypeptide chain to form a beta pleated sheet held together by hydrogen bonds
37
what is the tertiary structure of a protein?
when the secondary alpha helices and beta pleats fold further to give a complex and specific 3D shape held in place by hydrogen bonds between polar groups, disulphide bonds, ionic bonds hydrophobic interactions and hydrophilic groups
38
what are disulphide bonds?
covalent bonds formed between sulphurs in the R-group of the amino acid cysteine
39
what are ionic bonds?
between positively and negatively charged R-groups of amino acids
40
what are hydrophobic interactions?
between nonpolar R-groups which tend to cluster together towards the centre of the molecule
41
what are hydrophilic R-groups?
on the outside of molecules in contact with water
42
what are examples of proteins with tertiary structures?
antibodies, antigens & enzymes their tertiary structures are a specific shape to only one substance
43
how are tertiary structures denatured?
heat gives kinetic energy which cause hydrogen bonds to break first and then ionic bonds excessive heat will eventually break disulphide bonds (over 1000s degrees)
44
what is the quaternary structure of a protein?
proteins with more than one polypeptide chain formed by alpha & beta polypeptides / subunits eg - haemoglobin, catalase & collagen
45
what are the two main groups that the 3D shape of molecules can be divided into?
globular proteins fibrous proteins
46
what are globular proteins?
fold up into compact ball-shaped spherical structures hydrophobic R-groups turn inwards to the centre of the protein hydrophilic R-groups on the outside, water molecules can cluster around the protein, these groups form hydrogen bonds have metabolic roles (eg - enzymes & antibodies) soluble in water
47
what is haemoglobin?
globular protein with quaternary structure also a conjugated protein  2 a-polypeptide chains and 2 b-polypeptide chains alpha helices and small regions of beta pleated sheets in the secondary structure each chain contains a haem prosthetic group containing Fe2+ ion (oxygen binds to this) haem group gives blood it’s colour transports oxygen from the lungs to the respiring tissues for aerobic respiration
48
what is a conjugated protein?
protein with a prosthetic group (not part of the polypeptide chain)
49
what is catalase?
a globular protein & an enzyme quaternary protein containing 4 haem prosthetic groups presence of Fe2+ ions allows catalase to speed up the breakdown of hydrogen peroxide as it is damaging to cells if allowed to accumulate
50
what is an enzyme?
speeds up metabolic reactions has a specific shape active site for a specific substrate molecule
51
what is insulin?
a globular protein transported in blood a hormone involved in the regulation of blood glucose concentration fits into binding sites on specific receptors on cell surface membranes of muscle / liver cells secreted as pro-insulin Zn2+ helps dimers of insulin form haxamers
52
what are fibrous proteins?
formed from long, repetitive chains of amino acids insoluble molecules very little tertiary structure limited number of amino acids
53
what is keratin?
group of fibrous proteins present in hair, skin, nails & animal horns alpha helixes are held together due to many cysteine amino acids forming disulphide bonds more cysteine amino acids = more disulphide bonds = stronger structure nails have more disulphide bonds than hair so are less flexible forms strong, inflexible & insoluble molecules
54
what is collagen?
made up of 3 polypeptide chains wound around each other to form a triple helix long, strong, rope-like structure due to hydrogen bonds holding it together some flexibility found in the walls of arteries, tendons, bones & cartilage
55
what is elastin?
fibrous protein found in elastic fibres elastic fibres are found in the walls of blood vessels and in the alveoli gives structures flexibility to expand and return to normal size after  maintains blood pressure in arteries quaternary protein made of tropoelastin

Alevel biology (6 decks)

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