Metabolism Flashcards
What are the four classes of carbohydrates?
Monosaccharides
Disaccharides
Oligosaccharides
Polysaccharides
How can monosaccharides be classified?
Number of carbon atoms (triose, tetrose, pentose, hexose)
Isomer (D- or L-isomer)
In which isomeric form are most important sugars?
D-isomers
What is an isomer?
The same atoms but bonded together in a different 3D arrangement
What do glucose, fructose and galactose have in common?
They are all hexoses (6 carbons) which different arrangements of the same atoms
What do pentoses and hexoses normally form?
Cyclic molecules
Pentose - 5 membered rings
Hexoses - 6 membered rings
Name 2 important pentose monosaccharides
Ribose
Deoxyribose
Name 3 important hexose monosaccharides
Glucose
Galactose
Fructose
Name 4 important polyoligosacchardies
Starch
Cellulose
Glycogen
Dextrin
What is starch?
Branched polymer of glucose.
Formed either by a-1,4 (and) a-1,6 glycosidic bonds
What is cellulose?
Linear polymer of glucose
What is glycogen?
Extensively branched polymer of glucose
What is dextrin?
Branched oligomer of glucose
Breakdown product of starch and glycogen
What are the four main types of biologically important lipids?
Fatty acids
Triglycerides
Cholesterol
Cholesterol esters
What are fatty acids?
Hydrocarbon chains of various lengths
Name 2 differences between saturated and unsaturated fatty acids
Saturated
No double bonds between C atoms
Solid at room temperature
Unsaturated
At least one double C bond
Liquid at room temperature
What makes a triglyceride?
1 Glycerol
3 Fatty acid chain
Describe cis and trans fatty acids
Applies to unsaturated fat
Movement around the double C bond
Describe cis fatty acid
Loosely packed together, causes fatty chain to ‘kink’
Remember cis like cissy - floppy wrist, kink, 2 C,s 2 of the same
Describe trans fatty acid
Tightly packed together, chain continues on
What is a phospholipid?
A phosphate group attached to one or more fatty acid chains
How are phosphate groups attached to fatty acid chains?
Via glycerol or sphingosine
What is a glycolipid?
Carbohydrate (oligosaccharide) attached to one or more fatty acid chains
How are phosphate groups attached to fatty acid chains in modified lipids?
Via glycerol or sphingosine
What characteristic of phospholipids makes them essential?
Polar/non-polar nature, integral for membrane structure
Why are glycolipids important?
Cell surface recognition e.g. A and B blood groups
What are ketone bodies?
Small 4-carbon fatty acids formed by oxidation of fatty acids in the liver, especially during fasting
Why are ketone bodies important?
They provide energy substrates for the brain during fasting
How are ketone bodies linked to T1DM?
There is an excessive formation of ketone bodies during fasting which can result in dangerously high levels in the blood causing DKA
What creates the smell on the breath in DKA?
Acetone formed as a result of the breakdown of ketone bodies and exhaled
Give 5 roles of lipids
Fuels (fatty acids, ketone bodies)
Energy storage (triglycerides)
Transport between tissues (triglycerides)
Structural components of cell membranes (phospholipids)
Chemical messengers (diglycerides, steroids)
What type of process consumes ATP?
Anabolic process
What type of process produces ATP?
Catabolic process
Name the 3 parts of ATP
Adenosine
Ribose
3 phosphate chain
Describe the role water has in making ATP from ADP
ADP –> ATP = water is lost
ATP –> ADP = water is added
How is energy released from ATP?
By breaking up the high energy bonds between phosphate groups
Where is the only place ketones can not be used as an energy source?
The liver (synthesised there)
They are importantly used by the brain as substitute for glucose when it is not available
How is glucose stored in the liver?
As glycogen (a polymer of glucose)
Describe the relationship between fatty acids and glucose, and explain why this is important
Fatty acids can be formed from glucose, but not vice versa.
Glucose can be stored as lipids, but then can only be metabolised as lipids.
This is to save energy so fatty acids and glucose are not being used at the same time, and provides an energy storage solution
Name the 2 types of glucose transporters and state whether they are active or passive transporters
GLUT - passive
SGLT - active
What is the main difference between GLUT and SGLT transporters?
SGLT can transport Na+ as well as glucose
Which GLUT transporter has the highest affinity and where is it found?
GLUT-1
RBCs
Brain
Which GLUT transporter has the lowest affinity and where is it found?
GLUT-2
Pancreatic B-cell
Liver
Why is it beneficial to have a low affinity GLUT-2 transporter on a pancreatic B-cell and in the liver?
Because it will only uptake glucose if there is an excess of it in the blood.
This means that insulin will not be released prematurely into the blood stream by pancreatic B-cells, and the liver will only start to store glucose as glycogen if there is an excess of it in the blood, meaning more is readily available.
Which GLUT transporter is insulin sensitive?
GLUT-4
What is a lipid and what is it made from?
Glycerol
Fatty acids
Insoluble in water
What is the difference between mono- and poly-unsaturated fats?
Monounsaturated fatty acids have one C=C bond
Polyunsaturated have more than one C=C bond
What are the bonds in a triglyceride called?
How are they formed?
Covalent bonds
Condensation reactions
What is the difference between a triglyceride and a phospholipid?
Phospholipids only have 2 fatty acid tails, and have replaced the 3rd fatty acid with a phosphate group
Sucrose is made of:
Glucose and fructose
Lactose if made of:
Glucose and galactose
Maltose is made of:
Glucose and glucose
What 2 substances make up ketone bodies?
Acetoacetic acid
B-hydroxybutyric acid
What is the role of carbohydrates?
Energy source
What is the role of lipids
Energy source
Membrane components
Hormonal signalling
What is the role of proteins?
Enzymatic catalysis
Antibodies
Hormonal signalling
Structural proteins
Contractile proteins
Gas transport
What is the role of nucleic acids?
Information storage/transmission
Where can glucose be used as an energy source?
Most tissues - obligatory for brain and RBCs
Where can fatty acids be used as an energy source?
Most tissues - minimal in neurons as energy source
Where can amino acids be used as an energy source?
Not used by many fuel types - but are used by fast dividing cells e.g. enterocytes and cancer cells