2.5 Carbohydrates Flashcards
What function do carbohydrates serve in all organisms?
quick fuel and short-term energy storage
In what organisms do carbohydrates play a structural role?
woody plants, bacteria, animals such as insects
What are carbohydrates on cell surfaces involved in?
cell-to-cell recognition
What are carbohydrate molecules characterized by?
the presence of the atomic grouping H-C-OH in which the ration of H atoms to O atoms is 2:1
Why is the term “hydrates of carbon” used?
the ratio of H atoms to O atoms in the atomic grouping in carbohydrates is the same ratio as water
What is glucose?
a hexose sugar in our blood used as an immediate source of energy in our blood
What does “hexose” mean? Name some common hexoses.
hexose is a 6-carbon sugar
ie. fructose, galactose, glucose
How are hexose sugars similar
they all occur as ring structures with the molecular formula C6H12O6 (glucose)
How do hexose sugars differ?
the exact shape of the ring differs, as does the arrangement of the hydrogen (–H) and hydroxl (–OH) groups attached to the ring
What is a monosaccharide?
a simple sugar in which the number of carbon atoms i a molecule is between 3 and 7
What is fructose?
hexose sugar found in fruits
What is galactose?
hexose sugar found in constituents of milk
What is a disaccharide?
two monosaccharides that joined during a dehydration reaction
What is maltose?
a disaccharide formed when two glucose molecules bond together
What can break a bond between two monosaccharides?
our hydrolytic digestive juices
What is sucrose?
a disaccharide formed when glucose and fructose join and is used to sweeten food
ie. comes from sugarcane and sugar beets
What is lactose?
a disaccharide formed by glucose combined with galactose and is found in milk
What is a polysaccharide?
many monosaccharides joined together, long polymers that contain glucose subunits
What is starch?
a polysaccharide of up to 4000 glucose subunits that is a large storage form of glucose found in plants
*has fewer side branches (chains of glucose) that branch off the main chain than glycogen does
What happens after we eat starchy foods?
starch is hydrolyzed into glucose which will then enter the bloodstream
What is glycogen?
a polysaccharide that is a large form of glucose found in animals and humans
liver stores glucose as glycogen
What is the concentration percentage of blood glucose in the body?
in between meals, the liver releases glucose so that the blood glucose concentration is always about 0.1%
What is cellulose?
a polysaccharide that helps strengthen plant cell walls which allows non-woody plants to stand upright as long as they have an adequate supply of water
Why can’t humans digest cellulose?
the oxygen atoms in the linked glucose units are in an alternating up/down position
What is the importance of cellulose in our diet?
cellulose passes through our digestive tract as fibre or roughage
- necessary for good health
- may help prevent colon cancer
Who/what can digest cellulose?
herbivores can break it down and use it as glucose
What is chitin?
a structural polysaccharide found in the exoskeleton (shell) of crabs and related animals
- can be made into thread/suture material
What is deoxyribose?
a monosaccharide needed to make protein in DNA
What is ribose?
a monosaccharide needed to make protein in RNA
What test do you use to detect the presence of simple sugars? What colours does it change to and from?
Benedict’s solution
peacock blue to orange or brick red
What test do you use to detect the presence of complex sugars? What colours does it change to and from?
Lugol’s Iodine
orange to black
