1. Carbohydrates Flashcards
An individual sugar molecule is called a…
monosaccharide
Name a structural polysaccharide
Cellulose (plant cell walls)
What happens during hydrolysis
A water molecule is taken in to break down a chain of molecules.
Polysaccharides are large. This means that they are…
insoluble (will not dissolve)
Identify the monosaccharide
Galactose
When many monosaccharides join together, they form a…
polysaccharide
Which elements make up carbohydrates?
Carbon
Hydrogen
Oxygen
When 2 monosaccharides join together, they form a…
disaccharide
What happens during a condensation reaction?
A water molecule is released from the reacting molecules
How many covalent bonds does carbon make?
4
Which type of reaction takes place when two monosaccharides join together?
Condensation Reaction
Identify the monosaccharide
α-Glucose
A 3 carbon sugar is called a…
triose
A 6 carbon sugar is called a…
hexose
Name the bond that forms between two monosaccharides
Glycosidic bond
An individual biological molecule is called a…
monomer
Which type of reaction takes place when a disaccharide or polysaccharide is broken down?
Hydrolysis
Identify the monosaccharide
Fructose
Name 3 common disaccharides
Maltose (glucose + glucose)
Sucrose (glucose + fructose)
Lactose (glucose + galactose)
What is an isomer?
Molecules that have the same chemical formula but whose molecules are arranged differently.
Long chains of repeating molecules are called…
polymers
Glucose + Fructose –> _________
Glucose + Fructose –> Sucrose
The general chemical formula of a monosaccharide is…
(CH2O)nwhere n is the number of carbon atoms.
Glucose + Glucose –> _________
Glucose + Glucose –> Maltose
Identify the monosaccharide
β-Glucose
A 7 carbon sugar is called a…
heptose
Name the type of monosaccharide
Give its formula
Heptose
(CH2O)7
A molecule containing carbon is called an…
organic molecule
Name 4 common hexose monomers
α-Glucose
β-Glucose
Galactose
Fructose
Name 2 common storage polysaccharides
Glycogen
Starch
Name the type of monosaccharide
Give its formula
Triose
(CH2O)3
Which 4 elements make up most biological molecules?
Carbon
Hydrogen
Oxygen
Nitrogen
Glucose + Galactose –> _________
Glucose + Galactose –> Lactose
Polysaccharides are used in cells for _____________ and ____________
Storage (energy)
Structure (cell walls)
name the monomer that makes up maltose
glucose
sucrose hydrolysis produces..
fructose and glucose
How is the structure of cellulose suited to its function?
Long, straight/unbranched chains of β glucose Joined by hydrogen bonding To form (micro/macro)fibrils; Provides rigidity/strength;
What other enzyme is required for the complete digestion of starch?
amylase and maltase
Give 2 differences between the structure of cellulose and glycogen
cellulose moleculesstraightchains; glycogen branched
cellulose beta glucose; glycogen alpha glucose
celluose molecules straight chains; glycogen coiled
celluose has only 1, 4 glycosidic bonds; glycogen has 1,4 and 1,6 bonds
Describe and explain 2 features of starch that makes it a good storage molecule
coiled/helical making it compact insoluble so does not affect the WP of cells LArge so cant cross the cell membrane Branched so more ends for enzyme action
What bonds do amylose, amylopectin, glycogen and cellulose contain? numbers included
Amylose - 1-4 Alpha
Amylopectin - 1-4 and 1-6 Alpha
Glycogen - 1-4 and 1-6 Alpha
Cellulose - 1-4 beta
Describe how lactose is formed
glucose and galactose
join by condensation reaction
through a glycosidic bond
test which tests for starch?
iodine
What does it mean if a food sample turns benedicts solution this colour?
Low concentraiton of reducing sugar is present
What is a reducing sugar?
A sugar that can give an electron to the Copper (II) Sulphate found in Benedict’s reagent to make it form a red Copper (I) Oxide precipitate.
How would you carry out a Benedict’s rest for a reducing sugar
- Add 2cm3 of the food sample to a test tube
- Add an equal volume of Benedict’s Reagent
- Heat the mixture in a boiling water bath for 5 minutes
- Observe colour change - positive - brick-red precipitate
What do the following instructions describe a test for?
- Boil the sample with hydrochloric acid
- This will hydrolyse any disaccharide into 2 monosaccharides
- Cool solution and neutralise with sodium hydrogen carbonate
- Add Benedict’s Reagent and heat
- Observe colour change - brick red precipitate
Non-Reducing Sugars
Which two reducing sugars are released when sucrose is hydrolysed?
Glucose
Fructose
What do we mean when we say that the Benedict’s Test for Reducing Sugars is ‘semi-quantitative’?
That the colour of the result can be used toestimate the approximate amount of reducing sugar in a sample
What does it mean if a food sample turns benedicts solution this colour?
No reducing sugar is present
Name a disaccharide that is a non-reducing sugar
sucrose
What does it mean if a food sample turns benedicts solution this colour?
Medium concentration of reducing sugar is present
What does it mean if a food sample turns benedicts solution this colour?
High concentration of reducing sugar is present
During a Non-Reducing sugar test why do we need to neutralise the food sample after heating it in acid?
Because Benedict’s reagent will not work in acidic conditions (ideally alkaline)
What do the following instructions describe a test for?
- Add 2cm3 of the food sample to a test tube
- Add an equal volume of Benedict’s Reagent
- Heat the mixture in a boiling water bath for 5 minutes
- Observe colour change
A Benedict’s Test for a Reducing Sugar
What does it mean if a food sample turns benedicts solution this colour?
Very low concentraiton of reducing sugar is present
What does this picture show?
The results of Benedict’s test according to the concentration of reducing sugar present
What is a Non-Reducing Sugar?
A sugar that is unable to give an electron to the Copper (II) Sulphate in Benedict’s Reagent so itis unable to form a red Copper (I) Oxide precipitate
Which types of sugars are all reducing sugars?
Monosaccharides
How would you test for a Non-Reducing Sugar?
- Boil the sample with hydrochloric acid
- This will hydrolyse any disaccharide into 2 monosaccharides
- Cool solution and neutralise with sodium hydrogen carbonate
- Add Benedict’s Reagent and heat
- Observe colour change
The process of breaking a disaccharide up into 2 monosaccharides is called…
Hydrolysis
Name 2 common disaccharides that are reducing sugars
Maltose
Lactose
How is the structure of cellulose suited to its function?
- β-Glucose molecules can form long straight chains
- Parallel chains of cellulose form hydrogen bond ‘cross links’ which add strength
- Cellulose is arranged into microfibrils and then fibres, which add yet more strength
Which type of bond forms between adjacent α-glucose molecules in glycogen?
α 1-4 glycosidic bonds
Unbranched starch (amylose) coils into a…
compact helix structure
Which type of bond forms between branching α-glucosemolecules in glycogen?
α 1-6 glycosidic bonds
What test is described below:
Place 2 cm3 of the sample being tested into a test tube
Add 2 drops of iodine solution
A blue black colouration indicates a positive result
The test for starch
Identify the polysaccharide
Starch (amylose)
Identify the polysaccharide
Starch (amylopectin)
What form does starch take within plant cells?
Starch grains
Which type of bond forms between unbranched starch (amylose) molecules?
α 1-4 glycosidic bonds
Identify the polysaccharide
Cellulose
How is glycogen different to starch?
Glycogen has many more branches
What type of reaction occurs when monosaccharides join?
Condensation reaction
Which type of organism contains starch?
Plants
Identify the polysaccharide
Glycogen (more branches than starch)
What form does glycogen take in cells?
granules within muscle and liver cells
How would you test for starch?
- Place 2 cm3 of the sample being tested into a test tube
- Add 2 drops of iodine solution
- A blue black colouration indicates a positive result
Cellulose microfibrils are grouped are arranged in parallel groups called…
fibres
Which monosaccharide is cellulose made from?
β-Glucose
How does the structure of glycogen make it suited to its function?
- It is insoluble so does not cause water to move into the cell via osmosis
- It is large so does not diffuse out of animalcells
- It is compact
- It forms α-Glucose when hydrolysed for respiration
- Many more branches than starch allow α-Glucose to be released faster from glycogen
What is the function of glycogen?
an energy store for animal and bacterial cells
The coiled helix structure of unbranched starch (amylose) is held in place by…
hydrogen bonds
Which type of monosaccharide is glycogen made from?
α-Glucose
What is the function of cellulose?
- Cellulose is a major component of plant cell walls and provides rigidity to plant cells
- Stops plant cells bursting when water enters
How are parallel chains of cellulose held together?
hydrogen bonds
What structure does cellulose take?
Long unbranched chains that run parallel to each other
Which type of bond forms between branched starch (amylopectin) molecules?
α 1-6 glycosidic bonds
Which type of monosaccharide is starch made from?
α-Glucose
Which type of bonds joinβ-Glucose molecules when they form cellulose?
β 1-4 glycosidic bonds
Cellulose chains are arranged in parallel groups called….
microfibrils
Why does glycogen require more branches than starch?
Animal cells require more energy to function
How does the structure of starch make it suited to its function?
- It is insoluble so does not cause water to move into the cell via osmosis
- It is large so does not diffuse out of plant cells
- It is compact
- It forms α-Glucose when hydrolysed for respiration
- Many branches allow α-Glucose to be released fast
Name the 3 types of polysaccharide
Starch (amylose and amylopectin)
Glycogen
Cellulose
What is the main function of starch?
energy storage in plant cells
Describe the structure of glycogen
POLYMER of alpha glucose
joined by glycosidic bonds
branched structure
How does glycogen act as a source of energy?
branched chains are HYDROLYSED
into glucose
used in respiration
Starch
- Found as grains in plant cells - especially in seeds and storage organs
- Major energy source in the diet
- Not found in animal cells
Amylose
- Long unbranched chains of a-glucose
- Angle of glycosidic bonds give it coiled structure
- Compact - therefore good for storage as you can fit a lot in a small space
- Hydrogen bonds help hold structure
Amylopectin
- Long unbranched chain of a-glucose
- Branches mean there are many free end to allow enzymes to hydrolyse glycosidic bonds easily
Starch structure and functions
- Plants store excess glucose as starch
- Insoluble- doesn’t affect water potential
- Large and compact - allows a lot in small space
- Large molecule - difficult to leave cell - good storage molecule
Glycogen
- Excess glucose in animals
- A polymer of a-glucose with 1-4 bond and 1-6 glycosidic branches
- More highly branched, glucose released quickly by hydrolysis in muscles and liver
- Making glycogen from glucose is glycogenesis
Cellulose
- Polymer of B-glucose
- 1-4 b-glycosidic bonds
- Long unbranched chains
- Glucose are all rotated 180 degrees
- Straight cellulose chains
Cellulose structures
- The straight cellulose chains are held together by many weak HYDROGEN bonds. Large number of these make the microfibrils very strong.
- Prevents plant cells bursting by exerting an inward pressure - TURGIDTY
