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Biological molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are carbohydrates

A
  • made from monosaccharides (glucose, fructose, galactose)
  • contain C. H, O
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2
Q

What is glucose

A

A monosaccharide (monomers from which larger carbohydrates are made)
- a hexose sugar- monosaccharide w 6 carbon atoms
-alpha and beta (isomer-same molecular formula, but atoms connected differently
need to know structure of both

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3
Q

Condensation of monosaccharides

condensation- joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.

A

Condensation- joins two monosaccharides together with a new chem bond into a disaccharide.
a glycosidic bond forms between the monosaccharides and a water molecule is released

disaccharide example-
sucrose (glucose and fructose)
lactose (glucose and galactose)
maltose (glucose and glucose)

polysaccharides are formed through the condensation of many glucose units. they use glycosidic bonds, to form eg amylose

condensation of alpha glucose: glycogen and starch formed
condensation of beta glucose: cellulose formed

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4
Q

Hydrolysis of polymers

hydrolysis- breaks a chemical bond between two molecules and involves the use of a water molecule

A

polymers can break down into monomers through hydrolysis- it breaks the chemical bond using a water molecule

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5
Q

Benedicts test for reducing sugar

A

sugar=disaccharides and monosaccharides

Reducing sugar test- for all monosaccharides and some disaccharides (maltose and lactose)
- add benedicts regent (blue) to the sample and heat it in a water bath until it boils
- positive: forms coloured precipitate (solid particles in the solution)
colour change- blue>green>yellow>orange>brick red
higher the conc of reducing sugars, the further the colour change. you can compare the colours or for more accuracy you can filter the solution and weigh the precipitate

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6
Q

benedicts test for non-reducing sugars (eg sucrose)

A
  • for if the red sugars test came back negative

get new sample, add dilute hydrochloric acid, heat in boiling water bath
neutralise it with sodium hydrogencarbonate. then do the same benedicts test as the reducing sugar

positive test forms a coloured precipitate . negative test stays blue (means no reducing sugar either)

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7
Q

carbohydrate uses
starch is the main energy storage material in plants

A

starch is the main energy storage material in plants
cells get energy from glucose, they store the excess as starch, then break it back down into glucose when necessary

starch is a micture of amylose and amylopectin (two long unbranched chains of alpha glucose polysaccharides)

amylose- angles of the glycosidic bonds gives it a coiled structure. this makes it compact and good for storage.

amylopectin- side branches allow enzymes to get the glycosidic bolnds easily to break down molecules, glucose is released quickly :)

test for starch- add iodine dissolved in potassium solution to the test sample. If starch is present it goes from browny orange to dark blue black

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8
Q

carbohydrate uses,
glycogen is the main energy storage material in animals

A

animals get energy from glucose as well but they store excess as glycogen (polysaccharide of alpha glucose)

similar structure to amylopectin, but with more side branches, this means stored glucose is released quickly. it is a compact molecule, good for storage.

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9
Q

carbohydrate uses
cellulose is the major component of cell walls in plants

A
  • cellulose is made of long unbranched chains of beta glucose.
  • when bglucose bonds they form straight cellulose chains, which are linked together by hydrogen bonds.
  • they from strong fibres called microfibrils. cellulose provides structural support for cells.
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10
Q

Monomers

A

The smaller units from which larger molecules are made. eg monosaccharides, amino acids, nucleotides

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11
Q

Polymers

A

Molecules made from a large number of monomers joined together. eg starch, protein, dna

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12
Q

what are triglcerides

A

triglycerides are a kind of lipid

they have one molecule of glycerol with three fatty acid attached to it. fatty acids molecules have long tails made of hydrocarbons. the tails are hydrophobic, which makes lipids insoluble in water.
fatty acids all have the same basic structure but the hydrocarbon tails vary

fatty acids and glycerol are the monomers of lipids

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13
Q

how are trigycerides formed

A

triglycerides are formed through condensation reaction of one glycerole molecule and three fatty acid molecules (RCOOH) which forms an ester bond when a molecule of water is released. (done twice more to form a trigyleride)

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14
Q

Fatty acids can be saturated or unsaturated.

A

the difference between them is in the R group (hydrocarbon tails)

saturated fatty acids- no double bonds between carbon atoms. saturated w hydrogen

unsaturated fatty acids- at least one double bond between carbon atoms, this makes a kink in the chain

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15
Q

what are phospholipids

A

phopholipids are lipids similar to triglycerides

In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group.

the phosphate group is hydroPHILLIC, while the tail is hydroPHOBIC. this is important for the cell membrane

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16
Q

What is the structure of the lipid Triclyceride

A

triglycerides are mainly used as energy storage molecules. theyre good for this because-
- their long hydrocarbon tails contain lots of chemical energy so a lot of energy is released when theyre broken. the tails mean that it contains lots more energy per gram compared to carbohydrates. many C-H bonds=lots of energy

  • insoluble, so it doesnt affect water potential of the cell, no water comes in by osmosis, doesnt become turgid. triglycerides clump together as insoluble droplets within cells. hydrophobic tails on the inside and sheild themself from water with the glycerol heads. kind of like a dandilion.
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17
Q

what is the structure of the lipid, phospholipid

A

they make up the phospolipid bilayer of cell membranes. it controls what enters and leaves the cell.
they form a double bilayer with hydrophobic tails pointing inwards and hydrophillic heads pointing outwards towards the water. water soluble substances cant pass through it. It is a polar molecule

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18
Q

emulsion test for lipids (fat in food)

A

shake the test substance with ethanol for a minute so it dissolves, then pour into water.
if there are any lipids it will show up as a milky emulsion. the more milky it is, the more lipid there is

lipids emulsify in the water and form tiny droplets.
Lipids are soluable in inorganic substances such as alcohol, but insoluable in water

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19
Q

What are proteins made of

A

Proteins are made of more than one polypeptide
monomer of protein- amino acid
dipeptide- formed when two amino acids join together
polypeptide is formed when more than two amino acids join together through a condensation reaction.

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20
Q

what are the varibale groups of amino acids?

A

amino acids have the same general structure:
- a carboxyl group -COOH
- amine or amino gorup -NH2
- an R group/side group. The R group varies.
R
|
H2N—— C —— COOH
|
H

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21
Q

Polypeptides are formed by condensation reaction

A

amino acids link together through condensation to form a peptide bond, a molecule of water is released in the reaction.
the bonds formed between amino acids are called peptide bonds.
Dipeptides are formed by the condensation of two amino acids.
Polypeptides are formed by the condensation of many amino acids.

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22
Q

the four structural levels of proteins

A

PRIMARY STRUCTURE- sequence of amino acids in polypeptide chains

SECONDARY STRUCTURE- polypeptide chain isnt flat or straight. hydrogen bonds form between the amino acids in the chains.
This causes it to coil into an alpha helix or fold into a beta pleated sheet.

TERTIARY STRUCTURE- the coiled or folded amino acid chain is coiled or folded more.
more bonds form at different parts of the polypeptide chains. includes hydrogen bonds and ionic bonds (there are attractions between negative and positive charges on different parts of the molecule.
Disulfide birfges form when two amino acid cystein molecules come close together. the sulfur atom is one cystein bond to the bond of another.
for proteins made from a single polypeptide chain, the tertiary structure froms the final 3D structure.

QUATERNARY STRUCTURE- for proteins made of several different polypeptide chains held together by bonds. eg haemoglobin, insulin, collagen for these type of proteins. the q structure is its final 3d structure.

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23
Q

What are the functions of proteins
1) enzymes

A

different structures and shapes make them specialsed to particular jobs:

enzymes- roughly spherical shape because of tight foldings in the polypeptide chains. they are soluble and have metabolism roles. eg digestive enzymes and other enzymes used to synthesis (make) large molecules

24
Q

functions of proteins,
anitbodies

A

Antibodies are involved in immune responses. made of two light + short polypeptide chains, and two heavy + long polypeptide chains bonded together. antibodies have variable regions- the amino acid sequences vary greatly.

25
Q

functions of proteins, transport proteins

A

eg channel proteins in cell membranes. they contain hydrophobic, and hydrophillic amino acids which cause the protein to fold up and make a chanel. these proteins transport molecules and ions across membranes

26
Q

functions of proteins, structural proteins

A

strong, consist of long polypeptide chains that lie parallel to each other with cross links between them. eg keratin found in hair and nails, collagen found in connective tissues

27
Q

Biuret test for proteins

A

test solution needs to be alkaline, so

  • first add a few drops of sodium hydroxide solution
  • then add some copper(II) sulfate solution

if protein is present it turns purple, if it is not present it stay blue

28
Q

Enzymes as biological catalysts (6 things)

A

Enzymes speed up reactions.
1- enzymes catalyse metabolic reactions at a cellular level (resp) and for organisms as a whole (digest)
2- can affect the structure and functions in an organism eg resp and collagen production
3- can be intracellular or extracellular
4- theyre proteins
5- have an active site with a specific shape
6- enzymes are v specific bc of the tertiary structure

29
Q

Enzymes lower the activation energy of a reaction (energy needed to start the reaction)

A

activation energy is often provided as heat. enzymes lower the temp of the reaction.
when enzymes and substrates bind they form an enxyme-substrate complex because:
- if two substrates need to join to fit the active site of one enzyme, then being attached to the enzyme holds them closer together. this reduces repulsion between molecules–> bond more easily.
- if enzymes catalyse a breakdown reaction, fitting into the active site puts a strain on bonds in the substrates so the molecule breaks up more easily

30
Q

Induced fit model instead of lock and key model

A

enzyme-substrate complex changes shape slighly to complete the fit. substrate doesnt have to just be the right shape, it has to make the active site change shape as well.

31
Q

enzyme properties relating the their tertiary structure

A
  • enzymes are v specific, usually only catalyse one reaction. eg maltose only breaks down maltosebc only one substrate will fit into the active site.
  • shape of the active site is determined by the tertiary structure of the enzyme (which is determined by the primary structure)
  • this differs so every active site differs too.
  • if tertiary structure is altered (ph and temp), the active site will change, so substrate wont fit and enzyme cant carry out function.
  • primary structure (amino acid sequence) is determined by a gene. if a mutation occurs it could change the tertiary structure.
32
Q

temperature affecting enzyme activity

A
  • more heat, more kinetic energy–> reaction inc. (more likely to collide).
  • energy of collision also inc, so collisions are more likely to result in a reaction.
  • rise in temp causes enzymes molecules to vibrate, but if they vibrate too much at high temps, the vib breaks the bonds that hold the enzymes in shape, active site changes, enzyme and substrate no longer it (denatured, not a catalyst)
33
Q

ph affecting enzyme activity

A
  • enzymes have an optimum pH for the rate of reaction, above or below that have a lower rate of reaction.
  • if it is above/below the h+ and oh- ions found in acids and alkalines can mess up the ionic and hydrogen bonds that hold the tertiary structure of the enzyme together. Active site changes shape–> denatures
  • human enzymes work best at seven
  • pepsin works best at 2, good bc its in the stomach
34
Q

enzyme concentration affecting the rate of reaction

A
  • more enzymes, more likely collisions to form an enzyme substrate complex.
  • if the substrate amount is limited then there will be more enzymes than necessary that are able to bind, so no further effect.
35
Q

substrate conc affect the rate of reaction

A
  • the higher the substrate conc, the faster the reactions—> more collisions. only true up to a saturation point though. after that there are too many substrate molecules for enzymes to cope with bc all of the active sites are full. (no difference.
  • substrate conc dec with time during a reaction, unless more are added, and no other variables are changed. therefore the rate of reaction dec over time as well. the initial rate of reaction is the highest bc it is at the start.
36
Q

enzyme activity can be inhibited. competive inhibition

A
  • similar shape to substrate, they compete with them to bind to the active site. but dont lead to a reaction. they block the active site, substrate cant get in.
    the ratio of inhibitor to substrate can affect the speed of the reaction. more inhibitor- hardly any substrate will get to the enzyme. more substrate- chances of substrate getting there first increases
37
Q

enzyme inhibition. non competitive inhibition

A

nc inhibitors bind away from the active site, which make the active site change shape, substrate molecules cant bind. they dont compete to bind to the active site bc they have a different shape.
inc the conc of substrate has no effect , enzyme activity is still inhibited.

38
Q

DNA & RNA (Deoxyribonucleic Acid and Ribonucleic Acid)

A

Both carry imp info, found in all living cells, they are nucleic acid. They are polymers of nucleotides which is made up of
- pentose sugar deoxyribose for dna, ribose for rna (5 carbon atoms) ⬟
- nitrogenous base ▄ which varies adenine, thymine/uracil for rna, cytosine, guanine (AT. CG)complementary base pairings
- phosphate group ⬬

DNA: genetic info
RNA: transfer genetic info from dna to ribosomes (which read rna to make polypeptides aka proteins)

39
Q

Nucleotides join to form polynucleotides for both dna and rna

A
  • they join through a condensation reaction between the phosphate of one and the sugar of another aka sugar-phosphate backbone. This forms a phosphodiester bond (phosphate group and two ester bonds)
  • dna is made of two antiparallel (op dir) polynucleotide chains in a double helix structure
  • people doubted in the 1800s that dna carried genetic code, they thought protein did bc it was chemically varied. But by the 50s they proved it wrong and Watson and Crick showed it was a double helix structure

However rna has a single polynucleotide chain and isn’t double helix it is also shorter than dna polynucleotides

40
Q

DNA replication (semi conservative) genetic continuity between generations because half of the strands are from the original

A

DNA copies before cell division so each cell has the full amount of dna.
- enzyme dna helicase breaks the hydrogen bonds between the bases on the polynucleotide dna strands. This causes to helix to unwind/unzip into two separate strands
- the strands act as a template for the new strand, free floating dna nucleotides are attracted to the complementary exposed bases at/cg
- enzyme dna polymerase catalyses condensation reaction to join the nucleotides together. Forms phosphodiester bonds between the bases
- each new dna molecule contains one strand from the original and one new.

41
Q

DNA polymerase moves in opposite ways along antiparallel dna strands

A

3’ (3 prime) end and 5’ (5 prime) end.
The dna helix strands run in opposite directions (antiparallel)
The active site of polymerase is only complementary to the 3’ end, so the enzyme can only add nucleotides to the new strand at the 3’ end
Therefore, a new strand is made in the 5’ to 3’ direction so that polymerase moves down the template strand in a 3’ to 5’ direction.
Because the double helix is antiparallel, polymerase on one of the template strands is moving in the opposite direction to polymerase on the other template strand

42
Q

Semi conservative dna replication (Meselson and Stahl)

A

they validated Watson and Cricks semi conservative.
Conservative- original dna strands stay together, while new molecule has 2 (new?)dna strands.
m and s experimented with two isotopes of nitrogen. heavy N15, and light N14
- two bacteria samples grown, One in a nutrients broth containing light nitrogen, and one containing heavy. As the bacteria reproduces they took up the nitrogen to make nucleotides for new DNA. Nitrogen became part of the bacterias dna.
Sample of dna taken from each batch and put in a centrifuge. The heavy nitrogen settled lower down than the lighter nitrogen (bc it was heavier)
Then the bacteria grown in n15 was put in the n14 broth. Left for one round of replication. Dna sample taken and spun in centrifuge.
If it were conservative, the heavy dna would still be together (at bottom) and the light would be at the top.
If it were semi conservative, the new bacteria would be contain one strand of old, and one stand of new (both n14 and n15) the dna would be medium weight when spun in the centrifuge because it settles between them.
DNA settled in the middle which proves semi conservative replication.
@@ ## → @# @#

43
Q

Water properties

A
  • metabolite
  • solvent
  • high latent heat capacity of vaporisation
  • can buffer temp changes
  • very cohesive
44
Q

Water as a metabolite

A

A metabolite in metabolic reactions such as condensation (releases a molecule of water as a new bond is formed) and hydrolysis (needs one water molecule to break the bond) reactions eg amino acids→polypeptides (aka proteins) is a condensation reaction and energy from atp is released through a hydrolysis reaction.

45
Q

Water as a solvent

A

a solvent, other substances dissolve in it. Most metabolic reactions take place in solutions eg cytoplasm of eukaryotic cells and prokaryotic cells. lots of imp substances in metabolic reactions are ionic (made from one pos charged atom or molecule and one negatively charged atom or molecule). water is polar, the p end of the molecule is attracted to n ions, and vice versa. ions get completely surrounded by water and dissolve.

46
Q

Water has a high latent heat of vaporisation

A

It takes a lot of energy to break the hydrogen bonds between molecules. Lot of energy is used up when water. Useful bc water loss through evaporation can cool us down, eg sweat, without losing too much water.

47
Q

Water as a buffer

A

It can buffer (resist) changes in temp bc the hydrogen bonds absorb a lot of energy. Bc it has a high shc (lots of energy to heat up) this is useful, so organisms don’t experience rapid temp changes. It also makes it a good habitat as it remains a stable temp.

48
Q

Water as cohesive

A

very cohesive (stickiness or the attraction between molecules of the same type) which help water transport in plants and other organisms, also helps bugs land on water.

water is cohesive bc it is polar. cohesion helps water flow, good transport substance in columns up xylem. High surface tension when in contact with air- sweat forms in droplets which evap from the skin to cool it down. pond skaters and little bugs can walk on ponds

49
Q

Water structure

A

-H2o , two hydrogen and oxygen joined by shared electrons
- shared negative hydrogen electrons and pulled towards the oxygen atom. Other side of hydrogen is left with a slightly positive charge.
- unshared negative electron of oxygen give it a slightly negative charge
- this makes it polar. Partially negative δ- and partially positive δ+ the slightly negatively charged oxygen atoms attract the slightly positively charged hydrogen atoms of other water molecules. This is called hydrogen bonding.

50
Q

ATP (adenosine triphophate) is an immediate source of energy is a cell

A
  • plants and animal cells release energy from glucose (respiration)
  • cells can’t get energy directly from glucose.
  • In resp the energy released from glucose is used to make ATP.
  • ATP is made from the nucleotide base adenine ▬, combined w a ribose sugar ⬟, and three phosphate groups ●●●
  • once ATP is made, it diffuses to the part of the cell that needs energy
  • energy in ATP is stored in high energy bonds between the phosphate groups, released via hydrolysis reactions.
51
Q

ATP is quickly made and used

A
  • when energy is needed by a cell, atp is broken down into ADP (has two phosphates;diphosphate) and Pi (inorganic phosphate), this is a hydrolysis reaction.
  • phosphate bond is broken and energy is released, the reaction is catalysed by the enzyme ATP hydrolyse
  • ATP hydrolysis can be coupled to other energy requiring reaction in the cell, so the energy released can be used directly to make the couple reaction happen instead of being lost as heat
  • the released inorganic phosphate can be put to use by being added to another compound (phosphorylation) this often makes the compound more reactive
  • ATP can be resynthesised in a condensation reaction between ADP and Pi. it happens during resp and photosynthesis. it is catalasysed by enzyme ATP synthase.
52
Q

Inorganic ions

A
  • an ion is an atom or group of atoms w an electric charge
  • ion w a p charge- cation
  • ion w a n charge- anion
  • an inorganic ion doesn’t contain carbon
  • Inorganic ion can be found in a solution, in the cytoplasm of cells, and in the body fluid of organisms. Each ion had a specific role depending on the properties, an ion’s role determines whether it is found in high or low concs
53
Q

Iron ions are an imp part of haemoglobin

A

haemoglobin is a large protein that carries oxygen around the body and in rbc.
Made up of 4 different polypeptide chains, each with an iron ion (Fe^2+) in the centre
Fe^2+ binds to the oxygen in haemoglobin, when it is bound the fe2+ ion temporarily becomes an fe3+ ion until the oxygen is released

54
Q

hydrogen ions (H+) determine pH

A

pH is calculated based on the conc of hydrogen ions in the enviroment. the more hydrogen ions present, the lower the ph (more acidic) enzyme controlled reactions are affected by pH

55
Q

Sodium ions (Na+) help transport glucose and amino acids across membranes

A
  • glucose and amino acids needs help crossing membranes. a molecule of glucose or an amino acid can be transported into a cell across the cell surface membrane alongside sodium ions (Na+) which is cotransport
56
Q

Phosphate ions are an essential component of ATP and DNA

A

when a phosphate ion (PO4^3-) is attached to another molecule it is known as a phosphate group.
DNA, RNA, and ATP all contain phosphate groups.
-the bonds between phosphate groups store energy in ATP
-the phosphate groups in DNA and RNA allow nucleotides to join up to form the polynucleotides

Biology (8 decks)

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