Carbohydrates, Lipids & Proteins

Carbohydrates

• General properties:– Hydrophillic (dissolve in water)

– Generic chemical formula: (CH2O)n

• Glucose is a 6-carbon sugar…C6H12O6

– Generally have “root” names with “sacchar” as prefix, and/or “-ose” as suffix

• Glucose, sucrose, saccharide etc.

• Both sacchar- and –ose mean “sugar/sweet” in latin

Carbohydrates• Monomeric sugar: the simplest form

– Glucose, galactose (milk) and fructose• All are chemically: C6H12O6

• All are isomers of one another (same chemicals make them up, but they are arranged into different shapes)

Carbohydrates• Dimers of carbohydrates (2-monomers)

– Sucrose, lactose and maltose• Sucrose = table sugar• Lactose = milk sugar• Maltose…for malted beverages (beer etc.)

– In the diet, complex polymers of carbohydrates are digested into dimers first

• These dimers are then digested into monomers on the surface of the absorptive cells in the intestine

• You can’t absorb a dimer…you can only absorb a monomer

– Lactose indigestion = no lactose digesting enzymes

Carbohydrates

• Polymers of carbohydrates (polysaccharides)

– Long chains of sugar monomers

– Can be quite large (can be seen with a microscope…can crystallize)

Carbohydrates• Glycogen:

– Liver is the primary “body store” for glucose (in the form of glycogen)

• After a meal, blood glucose rises (digestion and absorption of dietary carbohydrates)

• Liver receives insulin signal to remove blood glucose (to restore homeostasis)

• Liver polymerizes glucose into glycogen• After a meal (like now), blood glucose drops (rest of

the body uses up the glucose in the blood)• Liver starts to break down glycogen into glucose and

releases glucose into the blood (to restore glucose homeostasis)

Carbohydrates• Glycogen:

– Formation of glycogen (making the glucose tree) = gluconeogenesis or glucogenesis

• Glycogen anabolism/polymerization = glucogenesis / gluconeogenesis

– Breaking down of glycogen (to free up glucose into the blood) = gluconeolysis

• NOT glycolysis or glucolysis (this is something different that we’ll cover later)

• Catabolism/digestion of glycogen = gluconeolysis

Carbohydrates• Starch:

– Primary glucose storage form in PLANTS• Made by photosynthesis (we make glycogen

by using the energy in ATP)

– The most significant source of dietary polysaccharides (carbohydrates)

Carbohydrates• Uses:

– Our bodies use carbohydrates (glucose) for ENERGY

• Any carbohydrates that are digested and absorbed are eventually formed into glucose (galactose and fructose are “converted”)

– Additional uses:• Attaching to proteins (glycoproteins…ie glycocalyx,

etc.)• Attaching to lipids in the plasma membrane

(glycolipid)

Lipids• General properties:

– Water insoluble (water and oil don’t mix)

– Similar chemical formula to carbohydrate (C-H-O), BUT:• VERY HIGH H:O ratio

– Tristearin (fat) = C57H110O6 (note how many more H there is than O)

Lipids• 5 types of lipid:

– Fatty acid (perhaps the most basic form…monomer)

– Triglyceride (can also be thought of as a basic form…but it’s made of 3 fatty acids)

– Phospholipid

– Eicosanoid

– Steroid

Lipids• Fatty acid:

– Chain of 4-24 Carbon atoms• On one end of the chain is a carboxyl group (-COOH-)

• On the other end is a methyl group (CH3)

– Thus…COOH-----C-C-C-C-C-C------CH3-

Carboxyl group (C+O+O+H)

Methyl group (C+H+H+H)

Lipids• Fatty acid:

– Chain can be “saturated” or “unsaturated”• Depends on the presence / absence of double

covalent bonds (C=C, versus single C-C)– Saturated = NO double bonds (C-C throughout)

– Unsaturated = at least 1 double bond (C=C somewhere along the chain)

» Mono-unsaturated = single C=C bond

» Polyunsaturated = 2 + C=C bonds

Lipids• Fatty acid:

– Chain can be “saturated” or “unsaturated”• Presence of a C=C double covalent bond

implies that you can add another C or anything else that can bind to the C=C

– This is why mono- and polyunsaturated fats/oils are considered “healthy”…because your body can attach stuff to them…saturated fats/oils can’t have anything more attached

Lipids

Lipids• Fatty acid:

– Most fatty acids can be made by your body/cells• BUT, there are some “essential fatty acids”

– we cannot make them (don’t have the enzymes to make them)

– Must be eaten or infused

Lipids• Triglyceride:

– 3 fatty acids covalently bonded to a glycerol (looks like a trident or 3-pronged fork without the handle)

Dehydration synthesis

1. Remove OH- from the glycerol head (called a glycerol “backbone”)

2. Remove H+ from the tails (3 fatty acids),

3. Attach the 3 fatty acid tails to the glycerol

Lipids• Phospholipids:

– Similar to triglyceride, but instead of 3 fatty acids, there are only 2 fatty acids• A phosphate replaces the 3rd fatty acid• Imparts hydrophilic nature (phospholipid

membrane)– Therefore, this kind of lipid is “schitzophrenic”

» Has hydrophobic (fatty acids) domain» Has hydrophilic (phosphate) domain» Called “amphiphilic”

Triglyceride

Phospholipid

Vs.

A “phospholipid” has 2 fatty acid tails, and 1 phosphate group. This phosphate group is hydrophilic (water friendly).

Lipids• Phospholipids:

– Important because every cell will be “made” of phospholipid• If every cell in your body were to be made of

pure fat/lipid, they would repel water…repel the ingredients in your blood

– No contact with water = no way to get nutrients, no way to communicate…we’

Lipids• Eicosanoids:

– All are derived from one single type of fatty acid (arachadonic acid)

– Hormone-like signaling molecules– Example: prostaglandins

• Where the C-C chains are re-arranged into rings

• Important during inflammation– The recent COX-2 drug recall (Vioxx, Celebrex)

were an attempt to permit prostaglandin synthesis but still give arthritis patients a working anti-arthritic drug

Lipids• Steroids:

– Primarily made in the liver

– Not present/available in plants

– BUT, despite no presence in plants, only about 15% of your total cholesterol is derived from your diet (liver makes the rest)

Lipids• Cholesterol confusion/controversy

– The advertising is actually incorrect … there isn’t a good/bad cholesterol …• The good/bad is actually a lipoprotein, not

cholesterol– A complex “bead” of cholesterol, fat,

phospholipid and protein

– BAD: low density lipoprotein (LDL) = full of lipid, cannot be “added” to

– GOOD: high density lipoprotein (HDL) = not full yet…body can still add to it

Lipids• Cholesterol confusion/controversy

– Remember the saturated and unsaturated fats (from the fatty acid slides)?• It is actually saturated fat that is “mislabeled”

as “bad cholesterol” rather than cholesterol itself

Proteins• The most important “molecules”

– Will make and break down carbohydrate

– Will make and break down lipids

– Will make and break down proteins

Proteins• Polymers of amino acid

– Amino acids are individual molecules made from a single carbon atom• Each carbon atom has a carboxyl and amino

side– Similar to a lipid, but instead of a methyl group

(CH3), there is an amino or nitrogen group (NH3)

• There are 20 different amino acids– Structurally, they are almost identical (1 central

Carbon, with carboxyl and amino groups)» Differences lie in a 2rd group (R-group)

attached to the Carbon

Proteins

Carbon Amino (NH3

-)Carboxyl (COOH-)

R-group

(aka radical)Unique “identifier”

Basic structure of amino acid

Proteins• The 20 amino acids are unique from one

another based on the “R-group” or “radical” attached to the carbon atom– This R-group can be hydrophobic

(hydrophobic amino acid)

– Can be hydrophilic (hydrophilic amino acid)

– Some can be polar and others are non-polar

Proteins• In order to polymerize amino acids (join them

together), you need to form a “peptide bond”– Bond is formed by dehydration synthesis (just

like carbohydrates and lipids)• Remove the hydroxyl (OH-) group from the

carboxyl portion of 1 amino acid• Remove the H+ from the amino portion of the

next amino acid• Covalently bind the two amino acids together

Proteins

Proteins

Proteins

Proteins• As you polymerize amino acids, just like with

sugars/carbohydrates…– Dipeptide = 2 amino acids– Tripeptide = 3 amino acids– Oligopeptide = 10-15 amino acids– Polypeptide = more than 15 amino acids

• Remember: despite the length of the amino acid chain, there will be only 1 amino group and 1 carboxyl group on the ENTIRE chain– AND, they will be on opposite ends of the amino

acid chain

Proteins• Protein structure is VITAL

– Different “levels” of protein structure• Primary structure = amino acid sequence

– Each protein is “unique” because of the order of the amino acids that are used to “make” it

» Recall that there are 20 amino acids…each protein is a unique arrangement of these 20 amino acids

Proteins• Protein structure is VITAL

– Different “levels” of protein structure• Primary structure = amino acid sequence• Secondary structure = coiled or sheet-shape within

the protein– Some amino acids can also interact with other

amino acids by “hydrogen bonds”» This interaction often results in structures like

an alpha helix (-helix), or» Beta sheet (-sheet)

– Many proteins have BOTH -helix and -sheet» Some even have multiple -helices and -

sheets

Proteins• Recall that some amino acids are

hydrophilic, and others are hydrophobic• An -helix (like a tube) can arrange

hydrophobic amino acids outwards, and place the hydrophilic amino acids INSIDE the helix, forming a “water tube”

– This is important for many membrane transport proteins

– The hydrophobic amino acids will interact with the lipid core of the plasma membrane

– The hydrophilic amino aids can interact with the fluid environment outside/inside the cell

C C

C C

C C

C

CVs.

C

CC

C

C

C

C

Insulin

Useless

Tertiary structure: the entire protein shape (remember that a protein can have many alpha helices and beta sheets…many areas of secondary structure)

Proteins• Thus, how you “shape” a protein is very

important in how it works– If the protein is not “shaped” correctly, it

will be useless• Useless proteins = wasted energy to make

them• Useless proteins can also be quite dangerous

(toxic)

Proteins• What do they do? (hint…EVERYTHING)

– Structure: for tissue structure & cell shape– Communication: hormones and receptors & other

signaling proteins• Hormones released by 1 cell can signal another

cell (hormones are proteins)• Hormone signals are “received” by receptors

unique to each hormone (receptors are proteins)• “second messengers” often utilize proteins

Proteins• What do they do?

– Membrane transport:• Membrane transport proteins (ion channels,

nutrient transporters, drug transporters) permit movement of molecules and compounds across a cell membrane

– Catalysts: enzymes are specialized proteins• Specialized for making or breaking bonds…chemical,

carbohydrate, lipid, amino acid etc.)

– Recognition and protection: immune recognition• Recall how each cell in your body has a “host

identifier” protein on it’s surface

Enzymes and metabolism• Enzyme: specialized protein that catalyzes a

reaction– Some “older” enzymes are still called by their “original”

names • Trypsin, pepsin etc.

– More common/scientific names will identify:

• Substrate (what the enzyme works on)… “___-ase”

– Carbonic anhydrase (works on carbonic acid)

» Anhydrase = remove water…remove water from carbonic acid

– Amylase (works on amyl…starch)

Enzymes and metabolism• Catalyze = help a reaction occur faster

– Enzymes do not “force” a reaction…they allow it to occur with LESS energy

• The reaction that an enzyme “catalyzes” would occur naturally without that enzyme, BUT, you would need much more energy and much more time

Enzymes

• Enzymes are SPECIFIC…they ONLY work on particular ingredients, and ONLY produce specific products – You have specific enzymes for “everything” that

needs to be anabolised and/or catabolised

• Enzymes recognize their substrates (the targets that they will either join or break apart) in an “active site”

Enzymes

• Active site: often relies on the specific arrangement of amino acids– Recall how they can interact at different levels

of protein structure

Enzymes

• Enzymatic process:– Substrate binds to the “specific” binding site in

the enzyme• Forms an “enzyme-substrate complex”

• Like a “lock and key”

– Enzyme will either join the substrates, or breaks them up (depending on the function of the enzyme)

Enzymes• Key features of the enzymatic process:

– The enzyme DOES NOT change during the process/reaction

• It might change shape, but the amino acid sequence remains the same

– The enzyme can usually perform its function (breaking or binding) many times before breaking down (wear and tear)

– This process isn’t always the same length of time

• Some reactions require more energy and others…therefore take more time than others

Enzymes• Enzymes must operate within:

– Optimal pH (outside of the optimal pH, the enzyme can be “denatured” or lose its structure)

• Remember the importance of protein “shape”

– Optimal temperature• Too cold = not enough energy • Too hot = denature structure

– This is why pH and temperature homeostasis are so important

• Out of homeostasis = enzyme malfunction … metabolism malfunction

Enzymes• Enzymatic activity can be altered by:

– Altering the amount of substrate (more = faster…to a point)

• Like the difference between simple diffusion and carrier-mediated transport of a molecule across a semi-permeable membrane

Enzymes

• Some enzymes also need organic co-factors– Specifically, some require “vitamins”

• “organic” because they have carbon (C-C-C) bonds, but are not proteins

– Vitamins or their derivatives (needed for some enzymes to work) are known as “coenzymes”

– “Vitamins” are organic molecules (carbon-based) that are “fortified” or added to the “first-world” diets

Enzymes

• Some enzymes interact with other enzymes (require 1 enzyme to finish it’s task before it can start)– “metabolic pathway” where a number of

enzymes work together

A BEnzyme 1

C DEnzyme 2 Enzyme 3

Intermediate reactions…. “intermediates”

• In a metabolic pathway, having “functional” enzymes is VITAL for the final outcome– If one enzyme does not work, the

following enzymes cannot do their task

A BEnzyme

1 C DEnzyme

2Enzyme

3

“intermediates”

• Glycogen storage disease (liver disorder):– Recall the glycogen, the storage form of glucose, looks

like a tree of glucose monomers– Each “branch and leaf” on that tree requires a particular

enzyme• hence glycogen production (gluconeogenesis) is a metabolic

pathway

– Glycogen storage disease has many forms: all stem from an individual defect in one of the many enzymes involved in building up the glycogen “tree”

• Without proper glycogen “production”, the patient usually suffers diabetes-like symptoms (inadequate blood-glucose homeostasis)

Without proper glycogen assembly, the entire glycogen molecule cannot be created. You then get this action…..

Because the entire glycogen molecule

cannot be assembled, blood glucose regulation is

hindered

Enzymes in your body• Various enzymes in your body do different things:

– Hydrolase: digest/catabolise products

• Digest fats, proteins, carbohydrates, nucleic acids– Esterase

– Carbohydrase

– Protease

– Nuclease

– Decarboxylase removes CO2 from substrates

– Isomerase changes the shape of a substrate (isomer)

– Deaminase removes NH2 (amine)from a substrate

– Dehydrogenase removes H from a substrate