Carbohydrates Lecture Notes

Carbohydrates - Glucose Glycogen Monomer – monosaccharides Most used carb sources: • • Glucose (used most for releasing energy, they can be in their linear form or their cyclical form), fructose and galactose. Ribose and deoxyribose. Disaccharides • • • Glucose + fructose (stable sugar that is used in coffee) Common: sucrose (table sugar), lactose (in milk) and maltose. 2 monosaccharides joined by Polysaccharides (when we join together more than two) • • • • Cellulose-main constituent of cell wall - Humans can’t digest - Bacteria can digest because they have the enzymes that cam Starch - Potatoes - Wheat The above two are almost identical but starch made out of alpha glucose molecules and cellulose beta monomers. Glycogen - How humans store excess glucose - Slightly different structure to starch so that we can release glucose molecules quicker. Polysaccharides • Cellulose in cell walls of the leaf. - They are bitter glucose molecules joined together in long chains, they form long fibres that is why when we eat things that have lots of cellulose in them we call them fibre. - Some starch in the leaf - One he has eaten the leaf; he will store all of the excess glucose from the starch in the form of glycogen. (glycogen alpha glucose it is structured in a slightly different way. It is branched, instead of being one long chain, it is more branched, meaning we cut the branches and release the glucose molecules when we need them. Glycogen • • • • Glucose is stored in animal tissues by the process of glycogenesis Glycogen usually stored in liver, but can be found in muscle cells because they use a lot of ATP so the need lots of glucose and glycogen laying around so that they can make ATP. Easily converted back to glucose to provide energy for cellular respiration. Can be stored in muscle for immediate access. Lipids - Phospholipids Fatty acids Cholesterol • • Non-polar molecules-hydrophobic 3 main types: - Triglycerides (when we have glycerol and three fatty acids) - Phospholipids (glycerol and 2 fatty acids) - Cholesterol (amphipathic: has sterol group and hydrocarbon chain and has polar head group, makes 30% of our cell membrane) • • Non-polar molecules -hydrophobic Fats- made up of a glycerol and fatty acids - Non-polar molecules – hydrophobic Triglycerides • Functions: long term energy storage – adipose tissue insulation/protective cushion (stops our organs from bouncing around) good for long term energy storage, so our adipose tissues is made out triglycerides. Can be saturated or unsaturated - Solid fat vs oil - • • • Those with double bond (their shape as if leg sticking out) because it has an unsaturated bond and it creates kink and creates a space between those fatty acids, so they do not back as closely. Phospholipids • • • • • • Glycerol, two fatty acid chains and a phosphate group Amphipathic Major constituent of cell membranes. Bilayer spontaneously forms when placed in water. (because head is water loving and tail is water hating so they want to be away from water and want to associate with one another. Form liposomes – important for drug delivery. Drug companies use this as a way delivery water solubles into cells or across really rich lipid membranes s they can put the drug inside and them make a liposome to carry over fatty membranes. Cell Membrane • • More unsaturated fatty acids – more fluid the membrane. Cholesterol: - Also, amphipathic Help to maintain membrane fluidity at lower temperatures. Facilitates cell signalling. - Can make up ~20% of the mass of the cell membrane so it will give stiffness to the membrane. The more cholesterol we have in the membrane the stiffer the membrane will be. Depending on how unsaturated the phospholipids are will determine how fluid the membrane is. - Some cells need to be more fluid than others. - Phospholipids can have different types of unsaturated tails in different phospholipids. (does that also apply for within the same phospholipid?) Cholesterol • Polar head group coupled to a steroid ring structure, and hydrocarbon tail. • • Precursor for key steroid hormones: have a sterol group. Forms the bases of steroid hormones. - Testosterone & estrogen - Because they are lipids, they can pass straight through our cell membrane. Hormones that can diffuse through the lipid bilayer and into our cells where they can act on receptors. - They do steroid hormones do not need to be transported across the membrane. - Sex steroids ✓ Testosterone ✓ Estrogen - Corticosteroids ✓ Cortisol (stress hormone) ✓ Aldosterone (important in electrolyte balance) Others • • Four main molecules of life - Nucleic acid - Proteins - Carbohydrates - Lipids Other molecules that play a role in physiology? - Metal ions – Na+, K+, Ca2+ - Mg2+ Iron in blood. Zinc – important in protein folding