Download Chapter 6 Digestion and Human Health

Digestion and Human
Health
The Molecules of
Living Systems
There are three main fluid components in your body
Cytoplasm in your cells
Fluid between your cells
Fluid in your blood
The also contain many different kinds of molecules and ions
Water, phosphates, hydrogen and sodium are examples of these
inorganic molecules
Organic molecules contain carbon bonded to other atoms such as
O, S, and N
Larger complex organic molecules are called
MACROMOLECULES
Types of Macromolecules:
CARBOHYDRATES
LIPIDS
PROTEINS
NUCLEIC ACIDS
Lets take a closer look at these!
How do they form?
All four types of molecules are formed and broken
apart in the same way:
. Dehydration SynthesisÆ the process by which larger
molecules are formed by the removal of water from two
smaller molecules
HydrolysisÆ the process by which larger molecules are
split into smaller molecules by the addition of water
CARBOHYDRATES
Always contain C, H and O – usually in the
same proportion
C: H: O in a ratio of 1:2:1
Carbohydrates provide energy for organisms
Two main types:
Simple sugars
Polysaccharides
Simple and Complex Sugars
1.
Monosaccharide Æ single unit sugars
Glucose, galactose and fructose
2.
Disaccharides Æ sugar composed of pairs of
monosaccharides.(maltose)
3.
Polysaccharides Æ large molecules composed of chains
of monosaccharide.
Structural Differences between Polysaccharides
Polysaccharide carbohydrates are formed by the
union of many monosaccharide subunits
Glycogen:
Are human polysaccharides formed from multiple
glucose units for long-term storage
Starches:
Are plants polysaccharides formed from multiple glucose
units for long-term storage
Amylase and Amlopectin
Note the more branches in a polysaccharide, the more
difficult it is to digest!
LIPIDS
1. Important in the storage of energy.
Glycogen supplies are limited in most animals;
however, once supplies are built up, excess
carbohydrates are converted to fat. This explains
why eating too many carbohydrates can cause an
increase in fat storage.
2. Cushions are delicate organs
3. Components in cell membranes
4. Carriers of vitamins (A, D, E, and K)
5. Hormone synthesis
6. Heat insulation
Insoluble in water
Store more energy than any other biological molecule
Some function as energy storage
Butter, lard ( solid at Room temperature) sunflower
oil, canola oil ( liquid at room temperature)
Three types of Lipids
Triglycerides
Phospholipids
Waxes
How do Fat molecules form:
Triglycerides
Formed from the union of
glycerol and three fatty
acids.
When solid at room
temperature they are
called fats.
When liquid at room
temperature they are
called oils.
PHOSPHOLIPIDS
WAXES
In waxes, fatty acids are joined in long-chain alcohols
or to carbon rings.
They are insoluble in water, hence their importance
in waterproofing plant leaves or animal feathers and
fur.
PROTEINS
Most structures are comprised of these molecules (hair,
nails, ligaments)
These are created from smaller subunits.
These are amino acids
Contain an central C atom, bonded to a H and to a
amino group, acid group and R-group
The R group distinguishes it to be one of 20 amino
acids from one another
**Our body can synthesize 11 of these
acids, 9 therefore come from our diet
we eat!
NUCLEIC ACIDS
Help with the growth and development of
organisms
They determine the cells function and its
characteristics
Two types: RNA and DNA
Genes are copied by RNA then makes a protein
These are long chains made up of smaller subunits
like our other macronutrients
DNA and RNA are made up of 4 nucleotides
Vitamins and Minerals
These are micronutrients
Essential for structure and function of our cells
Many help to give energy and decompose compose
Vitamins are organic vs Minerals that are inorganic!
Small amounts of each are needed for our bodies!
Minerals enable certain reactions to occur, build bones
and cartilage
Mineral absorbed by the blood stream – essential in
hemoglobin, hormones, enzymes, and vitamins!
Enzymes
biological catalysts (structures that speed up reactions)
made of proteins and have a specific shape
they are not changed or used up in reactions
they work by lowering the activation energy necessary
for a chemical reaction to occur (ie oxidation of
glucose: using digestive enzymes vs. lighting on fire)
How do enzymes work?
enzymes have folded surfaces that help to attract and bring together or
break up substrates (molecules on which the enzyme works)
Enzyme models
Scientists once believed that enzymes worked on a substrate molecule
like a lock and key – the “lock and key model” was proposed in the late
1800s by Emil Fischer. It was believed that a specific enzyme had a
specific shape only for a specific substrate and it would fit in perfectly.
A modified theory called the “induced-fit model” replaced the former
theory in 1973. The induced-fit model suggests that the active site of
the enzyme is altered slightly when the substrate molecules are trapped,
making the fit even tighter.
Sometimes enzymes need help in order to bind to substrates:
coenzymes – organic molecules synthesized from vitamins
cofactors – inorganic molecules such as Fe, Zn, K, etc.
Factors Affecting Enzyme Reactions
1. Temperature – a single enzyme can catalyze anywhere up to 30 million
reactions every minute - why do some reactions occur faster than others?
Enzymes operate at an optimal temperature of approx. 37°C (body
temp) – when temperatures get higher, enzymes denature (protein coils
unravel and the enzyme changes shape – therefore ineffective)
2. pH – all enzymes have an optimal pH range within which they work best
Because the folds in the protein (enzyme) are created by H bonds
(between negatively charged acid groups and positively charged amino
groups) – the addition of more H+ or OH- ions would affect the existing
H bonds – therefore altering the 3D shape of the protein.
3. Concentration of the substrate – Generally speaking, the greater the
concentration of the substrate molecules, the more collisions, therefore
the greater the rate of the reaction. However, once all of the substrate
molecules are occupied by enzymes, no more reactions can take place until
an enzyme comes free. Therefore, the extra substrate molecules will not
proceed until it can gain access to the active site on an enzyme.
What would the graph look like to illustrate the effects of concentration
of substrate on reaction rate?