Biological Molecules Flashcards
What shape does glucose have?
A ring shape
what elements do all carbohydrates have?
carbon, hydrogen and oxygen
Glucose has 6 carbon atoms and therefore is a….
Hexose sugar/monosaccharide
Glucose is a single sugar molecule and single sugar molecules are called….
Monosaccharides
Name 3 types of monosaccharides
Glucsoe, fructose, galactose
Why are monosaccharides soluble in water
They contain many OH groups (hydroxyl groups) allowing them to form hydrogen bonds with water molecules
Hydrophilic molecules are…
Molecules which are soluble in water
Glucose is a hexose sugar/monosaccharide, what does this mean
It has 6 carbon atoms
Which monosaccharide has 5 carbon atoms
Ribose
How can disaccharides and polysaccharides (larger carbohydrates) be formed
formed by the condensation of glucose molecules and the glucose molecules are joined by a glycosidic bond and a water molecule is formed too.
What glucose is it when the carbon-1 hydroxyl group points below the ring
Alpha glucose
What glucose is it when the carbon-1 hydroxyl group points above the ring?
Beta glucose
What are isomers?
Sams formula but different structure and properties
Alpha and beta glucose are called
Isomers of glucose
When do disaccharides form?
When 2 monosaccharides are joined together by a glycosidic bond in a condensation reaction
What is made when 2 alpha glucose molecules react?
Maltose
What is also made when we make a disaccharide?
A water molecule.
One hydrogen from one monosaccharide and one hydroxyl group from the other
What is it called when a reaction forms a water molecule
A condensation reaction
When we make maltose (disaccharide) what bond is formed?
A 1,4 glycosidic bond between the 2 alpha glucose molecules
In what reaction are disaccharides and polysaccharides formed in?
Condensation reaction because a molecule of water is produced
What happens when we add water to disaccharides or polysaccharides?
The glycosidic bonds break and this converts it back to the original monosaccharides
What is it called when we add water to a disaccharide/polysaccharide
Hydrolysis reaction
In cells hydrolysis reactions are normally carried out by
Enzymes
Monosaccharide + monosaccharide =
Disaccharide + water
Alpha glucose + alpha glucose =
Maltose + water
Glucose + fructose =
Sucrose + water
Glucose + galactose =
Lactose + water
Examples of disaccharides are
Maltose,sucrose,lactose
Examples of monosaccharides are
Glucose, fructose, galactose
Glucose is produced by plant cells using..
Using light energy trapped from photosynthesis
Glucose is a store of energy which can be released during….
Respiration
Why is glucose extremely soluble
It has a lot of hydroxyl groups which form hydrogen bonds with water molecules
Why are hydroxyl groups polar?
Due to small negative charge on the oxygen atom and the small positive charge on the hydrogen atom
Due to the hydroxyl groups being polar in glucose they can form hydrogen bonds with water molecules which makes….
Glucose highly soluble in water (hydrophilic)
What are the problems with the solubility of glucose? (plant cell)
If a cell contains a lot of dissolved glucose then water will move into the cell via osmosis
Instead the cell stores glucose as starch which is insoluble
Where is starch found?
In starch grains
How many molecules is starch consisted of?
2
Amylose and amylopectin
What is amylose?
An unbranched chain/polysaccharide of alpha glucose molecules formed in a condensation reaction
What happens when we join many alpha glucose molecules together to form amylose?
The amylose molecules twists into a compact helix with hydrogen bonds forming between molecules
What happens when the plant cell needs glucose?
Enzymes are used to break the glycosidic bonds in starch by adding water (hydrolysis)
What is amylopectin?
Amylopectin is a branched polymer of alpha glucose joined together by 1,4 glycosidic bonds and is made in a condensation reaction
Amylopectin has branches every….
25-30 glucose molecules
What are the branches in amylopectin
The branches are chains of alpha glucose molecules joined by 1,4 glycosidic bonds
How do amylopectin branches join to the main branch?
By a 1,6 glycosidic bond
Amylose forms a tight helix and so….
Makes starch a very compact compound
Starch is insoluble in water and so…
Does not cause water to move into the cell via osmosis
Amylose and amylopectin are polymers and so….
They are too big to diffuse out the cell membrane and out the plant cell
What happens when a plant cell needs glucose?
Enzymes are use to break the glycosidic bonds in starch by adding water (hydrolysis)
Where do enzymes break down the starch?
At the ends of the molecules
And because the amylopectin has a lot of branches it therefore has a lot of ends and so because of this emzymes can break down starch rapidly
What is the glucose storage molecule in animals?
Glycogen
Where are the major glycogen stores found?
Liver and muscle cells
What is glycogen?
A storage molecule in animal cells
Glycogen is a branched polymer of alpha glucose joined by 1,4 glycosidic bonds and it is formed in condensation reactions
the glucose molecules at the branch points are joined by 1,6 glycosidic bonds
What is more branched, glycogen or amylopectin?
Glycogen
Which makes it a VERY COMPACT MOLECULE
Glycogen has many branches and therefore many free ends which means…
why is this important?
That enzymes can break down glycogen into glucose very rapidly
This is important as animals have high rates of respiration
And the energy needs of an animal can change rapidly (running away from a predator)
Why is it good that glycogen is insoluble?
No water is drawn into the cell via osmosis
Why is it good that glycogen is a large molecule?
Because it cannot diffuse out the cell
What is a major part of the cell wall in plant cells?
Cellulose
What is cellulose
Cellulose is an unbranched polysaccharide of beta glucose and every 2nd beta glucose is flipped
It is flipped so it can form 1,4 glycosidic bonds
Cellulose forms a straight chain without any branches and so…
This allows cellulose molecules to get close together
And hydrogen bonds can form between neighbouring chains
A lot of these hydrogen bonds are formed which makes cellulose STRONG
What is it called when lots of cellulose chains group together?
A microfibril
Then microfibrils group together to form larger structures called MACROFIBRILS
and finally macrofibrils group together to form a cellulose fibre
What forms the cellulose cell wall
Cellulose fibres
What is the key feature of cellulose
Strength
Is the cell wall permeable to molecules like water?
Yes
Under normal conditions, do plant cells contain a lot of water?
Yes
What happens when water moves into a plant cell by osmosis?
The plant cells contents push OUTWARDS against the cellulose cell wall
The cellulose cell wall is strong enough to resist the outward pressure of the cell contents
This prevents the cell from bursting
What is it called when a plant cell is full of water?
Turgid
What gives plants an upright structure?
Turgid plant cells
Who loves you more?
Me (you can delete after u see this so it doesnt ruin ur flashcard 😭)
what is the scientific name for the molecules found in fats and oils?
lipids
lipids are a major source of ___ in the human body
energy
where do we find lipids?
in oils (olive oil) and solid fats (butter)
⬆️ both of these are rich sources of energy
as well as lipids being a source of energy, lipids are also used to ….
store energy
eg: adipose tissue in humans
where is adipose tissue found ?
under skin and around internal organs like the kidneys
explain adipose tissue
adipose tissue acts as an energy store and it also insulates the body reducing heat loss to the environment
lipids are used as w…..
waterproofing
for example: the oils that coat the feathers of aquatic birds
lipids are a major part of the structure of what?
membranes
eg the membranes that surround cells and mitochondria
what are the 2 main categories of lipids
TRIGLYCERIDES and PHOSPHOLIPIDS
what molecules do triglycerides contain ?
1 molecule of glycerol bonded to 3 molecules of fatty acids
what are the 2 parts of fatty acid molecules
at the end of the fatty acid we have a carboxylic group
the rest of the chain consists of a long chain of carbon atoms bonded to hydrogen
what do saturated fatty acids contain?
contain only single covalent bonds between the carbon atoms
what do unsaturated fatty acids contain
they contain at least 1 double covalent bond between the carbon atoms
what do monounsaturated contain?
only 1 double covalent bond in the carbon chain
what do polyunsaturated fatty acids contain ?
more than one double covalent bond in the carbon chain
imagine the structure of glycerol
…
how many hydroxyl groups do glycerol molecules have?
3 hydroxyl groups
glycerol and fatty acid molecules can react together to form a bond between eachother called a ___
and what is this process called ?
and 3 molecules of water are formed so what reaction is this?
ester bond
and this process is called esterification
condensation reaction
describe the process where fatty acids and glycerol are released in the digestion system .
how is this a hydrolysis reaction ?
in the digestion system lipase enzymes break ester bonds releasing fatty acid and glycerol molecules
⬆️ this reaction requires 3 water molecules and therefore it is a a hydrolysis reaction
are triglycerides polar or non polar
they are NON POLAR so they do not dissolve in water (hydrophobic) which explains why triglycerides are used for waterproofing
because triglycerides contain a large amount of carbon and hydrogen atoms ….
a lot of energy can be released from them
what does non-polar mean?
doesn’t dissolve in water (hydrophobic)
molecule is uncharged
how is the structure of PHOSPHOLIPIDS different to the structure of TRIGLYCERIDES?
phospholipids have 1 glycerol molecule bonded to 2 fatty acid molecules. and the glycerol molecule is also bonded to PHOSPHATE
what charge is the phosphate in a molecule of PHOSPHOLIPID
and is this part of the phospholipid (phosphate) hydrophilic or hydrophobic
the phosphate is negatively charged
in other words this part of the molecule is POLAR
because of this the phosphate is HYDROPHILIC (attracts water molecules/dissolves in water)
what is a simpler way to represent a phospholipid molecule?
a circle (the polar hydrophilic head) and 2 tails (non polar hydrophobic tails)
- the head group is the polar hydrophilic part of the molecule (phosphate)
- the tails represent the 2 fatty acid molecules which are non polar and hydrophobic
do phospholipids contain both a hydrophilic and hydrophobic region ?
yes
how do phospholipids act in water ?
and what do scientists call this structure ?
in water, phospholipids molecules position themselves so that the hydrophilic head groups can interact with water molecules while the hydrophobic tails cluster together, well away from water molecules
⬆️ scientist call this structure a PHOSPHOLIPID BILAYER
why is the phospholipid bilayer useful in cells?
the property is extremely useful as it allows phospholipids to form the membranes that we find around cells and within cells
what are all proteins formed from?
amino acids
how many amino acids are there?
20
what are the 3 parts of an amino acid?
amine group, carboxyl group and the R (variable) group
what is the “R” group in an amino acid?
it is a variable .
the R group is different for each of the 20 amino acids
Looking at the general formula of an amino acid, what elements do they contain?
what is the element that some amino acids contain ?
Carbon, Hydrogen, Oxygen and Nitrogen
Sulfur
how are dipeptides formed ?
where does this reaction take place?
how can this reaction be catalysed?
by the condensation of 2 amino acids and they are bonded by a peptide bond. and since it’s a condensation reaction a molecule of water is formed too
in the ribosomes
by a SPECIFIC enzyme
how do we make a polypeptide?
how many molecule of water are formed?
if we join 3 or more amino acids, then we make a polypeptide
we make a molecule of water for each peptide bond we make
how do we break a peptide bond?
to break a peptide bond, we need a molecule of water (hydrolysis reaction) and this reaction is carried out by the protease enzymes in the digestive system
or this hydrolysis reaction can take place by heating proteins with acid
what is the difference between an polypeptide and a protein
in order to be classed a protein, a polypeptide has to fold into a complex 3-dimensional structure
once it is folded into the correct shape, it can then carry out its function (for example a hormone or enzyme)
at this point we would refer to it as a PROTEIN MOLECULE
can proteins consist of several different polypeptides?
and can proteins contain other molecules helping them to carry out their function?
yes many proteins consist of many different polypeptides forming a large and complex molecule
yes proteins often contain other molecules helping them to carry out their function (haemoglobin)
how many levels are there in protein structure ?
4
what is the primary structure of a protein?
the primary structure is simply the specific order of amino acids in a polypeptide
why is the primary structure of a protein important?
because the primary structure determines the final 3 dimensional shape of the protein molecule
is the shape of a protein important for its function?
explain
yes
even changing a single amino acid in the primary structure can change the final shape of the protein
and this can prevent the protein from carrying out its function effectively
how is the primary structure of a polypeptide determined?
it is determined by the DNA sequence of the gene that encodes for that polypeptide
how do we form hydrogen bonds in a polypeptide chain?
what do hydrogen bonds cause polypeptides to do
looking at the polypeptide chain we can see that we have C=O groups and N-H groups.
the oxygen atoms have a small negative charge and the hydrogen atoms have a small positive charge
this means these charges can attract each other to form hydrogen bonds between amino acids all along the polypeptide chain
these hydrogen bonds cause the polypeptide to twist and fold into shapes and scientists call these twists and folds SECONDARY STRUCTURE
what is the most common secondary structure
and how is it formed
alpha-helix
the polypeptide is twisted into a helical shape held in place by hydrogen bonds
what is another secondary structure except alpha-helix?
and explain how it’s formed
beta pleated sheet
polypeptide folds into a flatter, sheet like structure again with hydrogen bonds between the amino acids holding it in shape
do many proteins have regions with alpha-helixes and beta pleated sheets ?
yes
the type of secondary structure formed depends on the primary structure in the region
certain amino acids are found in alpha helix regions and certain amino acids are found in beta pleated sheets regions
what does a molecule of water consist of?
what are the bonds between the oxygen and hydrogen atoms?
1 atom of oxygen chemically bonded to 2 atoms of hydrogen
covalent bonds
what are the charges in a water molecule?
because of these charges, what type of molecule is it?
what do the opposite charges mean?
the hydrogen atoms have a small positive charge and the oxygen atoms have a small negative charge
a polar molecule
opposite charges mean that water molecules are attracted to eachother and these forces out attraction are called HYDROGEN BONDS
are hydrogen bonds strong or weak?
weak
does a small volume of water have little or many hydrogen bonds
many
does water have a very high specific heat capacity ?
what happens when we heat water?
and because of this what does water act as?
this is an ideal habitat for which organism and why?
yes (we have to put in or take out a lot of energy to the change the temperature of water
when we heat water, the heat energy is used to break/weaken the hydrogen bonds rather than increase the kinetic energy of the water molecules
because of this water acts a buffer against rapid temperature changes, in other words the temperature of water tends not to change rapidly
this is ideal for aquatic organisms as they will not be able to function if the temperature of water changed rapidly in hot/cold days
which is less dense : liquid water or ice?
ice (ice floats)
ice is a HABITAT for a number of organisms what else does it do?
as well as acting as a habitat, ice also insulates the water below and prevents it from freezing and this means organisms can continue living
water has a very high latent heat of…
and what does allow organisms to do?
vapourisation (takes a large amount of heat energy to evaporate water)
to cool themselves without losing a great deal of water (sweating)
is one role of water as a solvent?
yes, water is an excellent solvent (lots of substances can dissolve in water)
do eukaryotic and prokaryotic cells contain a large amount of dissolved substances ?
like what ?
yes such as the chemicals in metabolic reactions such as respiration as well as the enzymes needed to carry out these reaction
what do bodies of water such as ponds and rivers contain?
dissolved oxygen and this is used by organisms in the water to carry out respiration
this makes water an excellent habitat for organisms
because water is a good solvent it is used to…
such as …
transport substances
for example blood plasma is the liquid part of blood and contains dissolved substances such as co2, ions (sodium ions) and chemicals such as glucose and amino acids
what is used to transport substances in the xylem vessels of plants ?
water
water in the xylem contains mineral ions such as the magnesium ion, magnesium ions pass through the plant roots from the soil. they are transported in the xylem from the roots to the leaves.
once in the leaves magnesium ions are used to make chlorophyll for photosynthesis
water molecules tend to stick together and scientists call this.?
and why does this happen
cohesion
this happens due to the hydrogen bonds between water molecules
what does cohesion allow in xylem tubes?
what else does cohesion cause? and why is it useful?
it allows long columns of water to travel in the xylem tubes and this makes water ideal as a transport medium in plants
SURFACE TENSION when water meets air,
it allows the surface of water to act as a habitat
is water important in metabolic reactions ?
how?
water is reactant and product in many metabolic reactions such as
hydrolysis
photosynthesis
respiration
condensation reactions
how can we hydrolyse disaccharides
by heating with acid or by an enzyme
how can lipids be hydrolysed into fatty acids and glycerol (3 ways)
1) heating with acid
2) heating with alkali
3)using the enzyme lipase at optimum temperature and pH
how can we hydrolyse proteins
heating w acid
by using protease enzymes
what are the products of enzyme reaction near to
they are near to specific carrier proteins used to absorb them
