Carbohydrates Flashcards
What are 4 main features of carbohydrates?
Highly oxidisable, store potential energy, structural and protective functions, cell-cell communication
What are three important hexose monosaccharides?
Glucose, Fructose, Galactose
What are three important disaccharides?
Maltose, Lactose, Sucrose
What links a disaccharide and on which groups?
Hydroxyl group binds to Anomeric carbon (1) by glycosidic bond
Where is maltose found/ how is it made?
In beer and baby food as sweetener. We don’t have much from our diets. Made from the breakdown of starch
Which disaccharides are reducing sugars and why?
Maltose and lactose. Anomeric C1 is available for oxidising, so they’re reducing sugars.
Where is sucrose found + what are its monomers?
Made by plants, found in sugar and processed foods. Glc + Fru
What are 4 ways to distinguish polysaccharides?
Monosaccharide units, length of chain, types of bonding, amount of branching
What are 2 subcategories of polysaccharides?
Homopolysaccharide (1 monomer only) and Heteropolysaccharide (2+ monomers)
What is starch and what glucose polymers does it contain?
Glucose polymer. Includes Amylose and Amylopectin
How often is there branching in amylopectin?
Every 24-30 glc monomers
Is starch reducing?
It has many non-reducing ends but few reducing ends
What is the structure of glycogen?
a-Glucose with 1-6 links every 8-12 monomers, so very branched
Where is glycogen mostly found in our bodies? (2)
In our liver to replenish blood glucose levels when we aren’t eating. In our skeletal muscle catabolising to ATP to allow our muscles to contract
Why are polymers a great form of storage for glucose? (2)
Many non-reducing ends to breaks down/forms very quickly. Very compact due to branching.
Glycoproteins structure
Protein with carbohydrates attached/associated with it
Features carbs bring to proteins (4)
Increase solubility, protect it from degradation, induce folds/conformation in protein, involved in cell-cell communication
Where are glycoproteins usually found? (6)
Plasma membrane, ECM, Cytoplasm and nucleus proteins, in the blood and in the Golgi apparatus
What is a glycosoaminoglycan (GAG) formed of?
A hexuronic acid and amino sugar alternating in an unbranched chain
Where are GAG’s found?
In the mucus and in synovial fluid around joints
What is a proteoglycan?
A GAG attached to proteins (e.g. cytokines). Mostly carb with attached protein
Where do we find proteoglycans on the body? (3)
On cell membranes attached to proteins, in the ECM and in the ground substance of connective tissue
What is mucosopolysaccharidosis?
Genetic disorder where enzymes cant break down GAG’s so they build up in cells, blood and ECM of connective tissue
What are some of the effects of mucosopolysaccharidosis? (5)
Heart and epithelial tissue damage, Stunted bone growth, Inflammad and damaged joints and sever dementia
Where does digestion of carbs occur in our body?
In the mouth and small intestine (duodunum and jejunum)
What 2 enzymes phosphorylise glucose and where are the found?
Glucokinase in the liver and hexokinase in other tissues
What benefit do Cellulose and Hemicellulose bring us?
Increase faecal bulk and decrease transit time
What are oligosaccharides and some examples in food?
Short monomer chain (with a1-6 ), not as large as polysaccharides. Peas, beans, lentils
How are carbs digested in the mouth and duodenum?
Amylase in saliva hydrolysed 1-4 bonds of starch
What are the 4 digestive processes in the jejunum and the name of the reaction?
Lactase, Glucoamylase (removes Glc), Sucrase, Isomaltase (1-6 bonds) - All Hydrolysis
What are the names of the first and middle part of the small intestine?
Duodenum and Jejunum
What are the products of carb digestion and where do they go?
Glc, Gal, Fru. They’re absorbed by the gut into the blood stream
What allows glucose to be absorbed by the gut and moved into the blood stream?
Low Na+ conc. in epithelial drives Na+ and glucose to enter the epithelial cell. Then glucose transports into blood through GLUT2.
What are some causes of disaccharidase deficiencies? (5)
Genetic inability to produce enzymes, Inflammation in gut, Damage to gut wall, removal of intestine, Intestinal infection
What are the symptoms of a disaccharidase deficiency?
Cramps or Abdominal distension
What is the cause and effect of lactose intolerance (2)?
Inability to produce lactase. Undigested lactase broken down in gut causing gas. Lactose also drags water from gut into lumen, causing diarrhoea
What are the enzymes that phosphorylase glucose and where can they be found?
Glucokinase in the liver and Hexokinase in all other tissues
What do terms Km and Vmax refer to?
Km refers to an enzymes affinity to a substrate. Low Km means an enzyme has a high affinity for a substrate (grabs on).
Vmax refers to the efficiency of an enzyme to catalyse a substrate. High Vmax = very efficient enzyme
What is the difference between Glucokinase and Hexokinase?
G in liver, H in other tissues.
G has high Km and high Vmax, so doesn’t grab many substrates but phosphorylises Glc quickly
H has low Km and low Vmax, so grabs a lot of substrate (good for low blood glucose level) but phosphorylises Glc slowly
What is the main fate of glucose/G6P?
To be converted to energy during respiration/oxidative phosphorylation in the liver, tissues or skeletal muscle
How is glycogen distributed around the body?
90% is in the liver and skeletal muscle for energy storage, 10% in the blood
What is the livers role in glucose storage?
Glucose is converted to G6P and stored as glycogen. When blood Glc levels are low, glycogen is broken down and converted from G6P back to glucose, to be released into the blood
What is skeletal muscle’s role in glucose storage?
Glucose phosphorylises into G6P and then glycogen forms. When required, glycogen breaks down to G6P, but can’t return to Glc, so converts through glycolysis to lactate to make ATP
How is Glycogen degraded?
Glycogen phosphorylase removes Glc from non reducing ends, producing G1P monomers. Debranching enzyme removes 1-6 bonds
How is Glycogen synthesised? (3 steps)
(1) Glycogenin forms short glucose chain. (2) Then Glycogen synthase adds further glucose molecules. (3) Branching enzyme breaks chain and reforms it as a 1-6 bond.
