Carbohydrates Flashcards
what are the three types of simple sugars found in nature?
glucose
galactose
fructose
what are simple sugars made up of?
six carbons (hexoses)
what are common types of disaccharides and what are they made up of?
sucrose - glucose + fructose
lactose - glucose + galactose
maltose - glucose + glucose
what are the different types of polysaccharides classified?
branched or unbranched
homeopolysaccharides or heteropolysaccharides
how can the branching of a polysaccharide be written as?
unbranched (linear) - alpha 1-4
branched - alpha 1-6
which disaccharides can or can’t be oxidised?
maltose and lactose can be oxidised
sucrose can’t be oxidised
what are the types of starch in plants and their prevalence in starch?
amylose (20%)
amylopectin (80%)
what is the animal variant of starch, and where is it found?
glycogen
found in liver and skeletal muscle
what is the difference between glycoproteins and proteoglycans?
proteoglycans - made up of GAG and protein. form part of ECM, are found in cell membranes
glycopeptides - can be involved in lots of functions, most proteins have carbohydrates attached
what are glycosaminoglycans?
cells secreting mucus, made up of hexuronic acid + amino-sugar
what are disorders caused by GAG imbalance, and what is an example?
mucopolysaccharidoses
eg Hurler’s syndrome
what enzymes break down carbohydrates and where?
mouth - salivary amylase
duodenum - pancreatic amylase
jejunum - lactase, sucrase, maltase, isomaltase, glucoamylase
how is glucose taken up by the blood?
from gut to endothelial cell (through ATPase pump)
from endothelial cell to blood (through GLUT 2 protein)
which protein transports which carbohydrate monomer to the blood?
glucose and galactose - GLUT2
fructose - GLUT5 (concentration gradient)
where is glucose stored?
in glycogen (liver and skeletal muscle)
what is the first thing that happens when glucose enters liver and other tissue cells?
liver: glucokinase adds phosphate and traps glucose in cell
other tissues: hexokinase adds phosphate to trap glucose in cell
what are the affinity and efficacy of glucokinase and hexokinase?
glucokinase - high Km and high Vmax
hexokinase - low Km and low Vmax
how is glycogen formed?
glycogenin binds glucose to itself
glycogen synthase continues the job
glycogen branching enzyme adds more glucose
how is glycogen broken down?
glycogen phosphorylase - removes glucose1phosphate
glucose 6 phosphatase - removes phosphate and allows glucose to leave cell
which glycogen breakdown enzyme is only present in liver cells?
glucose 6 phosphatase
what are two examples of disorders caused by lack of glucose 6 phosphatase or glycogen phosphorylase?
Von Gierke’s disease (no phosphatase in liver)
McArdle’s disease (phosphorylase in skel muscle)
how many steps are there in glycolysis?
10
which steps of glycolysis are spontaneous and therefore irreversible?
1, 3 and 10
what characterises glycolysis in terms of oxygen need?
it doesn’t require any oxygen