Carbohydrates Flashcards
What is the general formula for carbohydrates?
(CH20)n
How are carbohydrates formed
Primarily by photosynthesis
1) light dependent reaction
2) light independent reaction
Name the basic unit of carbohydrates?
Monosaccharides
*Give examples of some food in which carbohydrates are found (7)
- Bread
- Beans
- Milk
- Popcorn
- Potatoes
- spaghettis
- soft drinks
*Give some common forms of carbohydrates
- Sugars
- Fibres
- Starches
What are disaccharides?
Two simple sugars linked by a covalent bond
What are polysaccharides?
They are hundred or thousands of monosaccharides
Give some examples of polysaccharides
- Starch
- Glycogen
- Cellulose
How are monosaccharides commonly found in humans classified?
According to the number of carbons they contain in their backbone structure
How many carbon atoms do the major monosaccharides contain?
4-6
How are carbohydrates formed in plants?
By photosynthesis from carbon dioxide and water in the precise of sunlight
Other than photosynthesis how else can glucose be synthesised?
glucose can be synthesized from other organic molecules in processes of gluconeogenesis
In animals what is glucose synthesis called?
gluconeogenesis
What does gluconeogenesis usually start with in animals?
Can start with lactate, amino acids or glycerol
How is lactate produced in animals?
produced by anaerobicglycolysis
Where are amino acids derived from in animals?
From the breakdown of protein
How is glycerol produced in animals?
Produced by the breakdown of lipids
What is a glycogenic amino acid?
It is an amino acid that can be converted into glucose through glycogenesis
Give examples of glycogenic amino acid
Alanine Arginine Asparagine Asparticacid Cysteine Glutamicacid Glutamine Glycine.
Name the most commonly occurring monosaccharides
- Fructose
- Glucose
- Galactose
What is fructose found in?
Fruits
Honey
Vegetables
What can fructose be derived from?
Can be derived from the digestion of sucrose
What is glucose found in?
Small amounts are found in some fruits, vegetables and honey
Commonly found in manufactured foods
What can glucose be derived from?
The digestion and conversion of other carbohydrates
What can galactose be derived from?
The digestion of lactose
Are disaccharides taken up by cells?
Disaccharides are not taken up by cells
How are disaccharide formed?
A covalent bond between the anomeric hydroxy of a cyclic sugar and the hydroxyl of a second sugar forms a glycoside
What is the covalent bond between the anomeric hydroxy of a cyclic sugar and the hydroxyl of a second sugar called?
Called a glycosidic bond
Name some nutritionally important disaccharides
- Sucrose
- Lactose
- Maltose
*Where is lactose found?
Found exclusively in the milk of mammals
*What is lactose made up of?
Consists of a galactose and glucose in a beta-(1-4) glycosidic bond
What is an amino acid that can be converted into glucose called?
A glycogenic amino acid
What is sucrose derived from?
Derived from sugar cane and sugar beet
*Where is sucrose found?
produced naturally in plants
- Sweet root vegetables like BEETROOT and CARROTS
- Sugar canes and sugar beets
- Table sugar
- Manufactured food
*which type of plant stores the most sucrose?
sugar canes + sugar beets
table sugar + sucrose in processed foods are extracted from ^
*what is maltose produced from??
from fermented germinated grain like:
barley
rice
malted barley (maltose)= source of sugars which are fermented into beer by yeast
*What is maltose?
alpha-(1-4) glycosidic bond
intermediate in intestinal digestion of starch + glycogen
natural sweetener
*where do we find oligosaccharides?
- partial breakdown of polysaccharides
- naturally occurring: found in plants
*Name the predominant monosaccharide found in polysaccharides
D glucose
*Name the main polysaccharides
- Glycogen (can digest alpa 1-4/1-6 bonds= digestable)
- Starch
- Cellulose (can’t digest BETA 1-4 glycosidic bonds)
composed of D glucose
Name the major form of stored carbohydrates in animals
Glycogen
Which molecules make up glycogen?
A homopolymers of glucose in an alpha-(1-4) linkage
Is glycogen branched or unbranched?
It is highly branched with alpha (1-6) branch linkages occurring every 8-10 residues
Every how many residues does branching occur in glycogen?
Every 8-10 residues
How is glycogen so compact?
Due to coiling of the polymer chains
Gives some advantages of glycogen been highly coiled
Means it is compact so a large amount of carbon energy can be stored in a small volume with little effect on cellular osmolarity
*Name the major form of stored carbohydrates in plant cells?
Starch
What is the main difference in the structure of glycogen and starch?
Theres less branching in starch
Every how many residues does branching occur in starch?
Every 20-30 residues
*Name the 2 main types of starch
- Amylose = 20/30% of starch
UNBRANCHED
alpha 1-4 glycosidic bonds - Amylopectin= 70/80% of starch
BRANCHED
alpha-d- glucose 1-4 bonds
AND 1-6 glycosidic bonds at branch points
2. Amylopectin
*what is the most commonly consumed carb?
starch
Amylopectin is branched starch
How is amylose digested and what are its digestion products?
Enzymes in the digestive tract degrade amylose to generate GLUCOSE
The major product of amylose digestion is maltose
Can cellulose be digested by humans?
No as humans don’t have an enemy to degrade the beta 1-4 linkage
What is cellulose the principle component of?
dietary fibre (Roughage)
What is Roughage?
It is the fibrous indigestible material in vegetable foodstuffs which aids the passage of food and waste product though the gut
What does roughage aid?
The passage of food and waste product though the gut
What does fibre help with?
Helps to ensure good gut function by increasing the physical bulk in the bowel and stimulating the intestinal transit
What are monosaccharides and disaccharides used for?
- Energy source
- Glycosylation of proteins
- Structural components
- Carbon skeletons fro biosynthesis of amino acids
What are the functions of glucose?
- It is used by all cells as an energy source
- Some glucose is converted to ribose and deoxyribose
- Glucose can be utilised to make the molecule NADPH
- Biosynthesis of lipids and amino acids from Sugar
Which organ redistributed glucose back into the blood?
LIVER
What happens to the majority of glucose entering out body?
About 70 percent of the glucose entering the body from digestion is redistributed (by the liver) back into the blood for use by other tissues.
Where does the energy from glucose come from?
Comes from the chemical bond between the carbon atoms
Name the 2 ways glucose can be broken down
- Aerobic respiration
2. Fermentation
How is glucose broken in aerobic respiration?
- Glycolysis of glucose forms Pyruvate
- This relates to ATP molecules
- Pyruvate is oxidised
- Krebs cycle occurs
- Electron transport chain occurs which releases unto 36 ATM molecules
What can glucose be fermented into?
- Alcohol and CO2 (in bacteria and yeast)
2. Lactic acid (in animals)
What aids the passage of food and waste product though the gut?
Roughage
What happens to excess glucose in the body?
Excess glucose is stored as glycogen
If all of the energy, glycogen-storing capacity, and building needs of the body are met, excess glucose can be used to make fat.
Where is the majority of glycogen stored?
In the muscles and liver
What are ribose and deoxyribose essential for?
They are the essential building blocks of important macromolecules such as RNA, DNA and ATP
When is glucose stored as fat?
When all of the energy, glycogen-storing capacity and building needs of the body are met
What is the raw material for amino acid synthesis obtained from?
Glucose
How many naturally occurring amino acids are therer?
20
What is lipid metabolism associated with?
Associated with carbohydrate metabolism as products of glucose can be converted into lipids
*What is a high level of sugar consumption associated with?
Greater risk of tooth decay
high proportion of sugar in diet = higher risk of high energy intake
What might drinking might sugar beverages lead to?
Weight gain and increased BMI in teenagers and children
Also increases the risk of developing type 2 diabetes
What is the recommended amount of carbohydrates a person should consume?
Total carbohydrates contributes 50% towards daily energy requirements
How much of your daily energy requirement should come from free sugars?
5% of daily energy requirement
How much of your daily energy requirement should come from natural sugars?
45% of daily energy requirements
What is the recommended dietary fibre intake for an adult
30g/day
What is the average fibre intake in the UK?
12g/day
*what bonds can we digest?
alpha 1-4 glycosidic bond
alpha 1-6 glycosidic bond
*which bonds can we NOT digest?
beta 1-4 glycosidic bonds
*where is starch found?
1) cereal grain- rice, wheat
2) root vegetables (potato)
- why is glycogen suited for storage?
so heavily branches (1-6)
insoluble
can not pass cell membrane
*so what does glycogen do in our bodies?
glucose gets used up fuelling cell activities
when level of glucose in blood decreases glycogen gets broken down back to glucose units
-> glucose re enters blood
*what happens in the light dependent reaction of PS?
light energy -> chemical energy
by taking:
- photon
- water
produce oxygen
as well as ATP, NADPH
*what happens in the light independent reaction of PS?
calvin cycle
co2 + atp + nadph -> glucose
*why would we need to do carb synthesis?
if fasting/ starving
blood sugar level becomes low
body will synthesis glucose
from other organic molecules
(= gluconeogeneis)
*why does glucose level in blood need to be maintained?
because it is used by cells to make:
- energy molecule (ATP)
*precursors for gluconeogenesis? (3)
1) glycerol (breaking down of triglycerides in adipose tissues)
2) lactate (produced by anaerobic metabolism)
lactate= transported back to liver where it is-> converted into pyruvate
3) glycogenic amino acids (derived from breaking down of proteins)
-> converted into
pyruvate
oxalacetate (intermediate of citric acid cycle)
pyruvate + oxalacetate- used to make glucose
*so once gluconeogenesis occurs in the liver, what happens to the glucose?
made in liver, released in bloodstream, travels to cells all over body
to be used for energy
*function of carb as an energy source?
biological fuel source for living
all body cells are capable of using glucose to generate energy
*function of carb as an energy source?
biological fuel source for living
all body cells are capable of using glucose to generate energy
body prefers glucose as an energy source
*how is glucose used to generate energy?
through a series of complex biochemical reactions
breaks down glucose
yields ATP (energy molecules)
= GLYCOLISIS
glucose -> pyruvate (ATP produced)
if adequate oxygen=
*how does glucose actually give us energy though?
comes from chemical bonds between carbon bonds
body cells break this bond
capture that energy to perform cellular respiration
*what happens if there is adequate oxygen available following the production of pyruvate?
glucose does aerobic respiration
pyruvate converted to -> acetyl CoA -> moves through Kreb’s cycle
THEN -> move onto ETC (where majority of ATP is produced + most of the energy comes from)
*what happens if there is INADEQUATE oxygen available following the production of pyruvate?
pyruvate converted -> lactic acid
transported to liver
to be converted into glucose
-> moves to blood to maintain constant supply of:
- ATP for tissues
- glucose in blood
*role of liver + glycogen: (3)
- glycogen quickly disseminates glucose to other tissues/ body cells when they are low on glucose
- liver stores 1/4 of total bodily glycogen
- liver regulates blood glucose levels between meal times at normal range
*which macromolecules does glucose help make?
glucose converted to:
1) ribose
2) deoxyribose
(essential parts of RNA, ATP + DNA)
glucose is used to make:
1) NADPH
*why do we need NADPH? (2)
= antioxidant
protects us against oxidative stress
used in many chemical reactions in body
(NADPH is like the shield, and oxidative stress is the enemy attack)
*how are amino acids synthesised?
at the cost of ATP
by breakdown of glucose in glycolysis
- summary of glucose’s uses:
used to make
- deoxyribose/ ribose
- nadph (antioxidant)
- atp
- lipids (fatty acids)
- amino acids
- energy store (glycogen)
- energy fuel (glycolysis to make ATP)
- many plants/ bacteria can synthesise how many amino acids?
20 (all)
