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Nutrition
Digestion
Excretion
Science in Our Lives II
Unit 1
Nutrition
 Definition
 Process of taking materials from environment and changing
it to a usable form
 Essential nutrients for life include lipids (fats), proteins and
carbohydrates
 Also important are vitamins, minerals, fiber and water
 Functions: growth, repair, regulatory molecules (enzymes,
hormones), energy
Nutrient Composition
 What makes up a nutrient?
 Water is made up of hydrogen and oxygen molecules
 Vitamins and minerals are made up from numerous elements
from the periodic table such as iron and calcium
 The main building blocks of nutrition include:
 Proteins (which are made by connecting amino acids together)
 Lipids or fats (which are made by connecting 3 fatty acids
together with 1 glycerol molecule)
 Carbohydrates/starches (which are made by connecting simple
sugars together
Nutrient Composition
Protein Example
- Notice that this protein
(the entire purple strand)
is made up of individual
amino acids
Ex. Enzymes, hormones, connective
tissue, chlorophyll, hemoglobin
Function: structure, function
Nutrient Composition
Fat (or Lipid) Example
- Notice the 1 glycerol
molecule and the 3 fatty acids
that make up a fat molecule
Ex. Oils, waxes, etc.
Function: energy
Nutrient Composition
Carbohydrate Example
- Notice how simple sugars (like
glucose) join to form a carbohydrate
Glucose
(a simple
sugar)
Glucose
(a simple
sugar)
Ex. Simple sugar = glucose
Complex sugar = starch
Function: energy
Maltose
(a carbohydrate)
Two types of Nutrition
 Autotrophic Nutrition
 The organism MAKES its own
nutrients using a process called
photosynthesis
 Ultimate nutrient produced is
glucose (a simple sugar)
 Organisms who make their own
food are called AUTOTROPHS
or PRODUCERS
 Example: All green plants
ODDITY: HETEROTROPHIC PLANTS!
 Heterotrophic Nutrition
 The organism must obtain
nutrients from its environment
by grazing plants or eating other
organisms
 Photosynthesis is NOT possible
by these organisms
 Organisms who must find
nutrients because they cannot
make their own are called
HETEROTROPHS or
CONSUMERS
 Example: All animals
Autotrophic Nutrition
Photosynthesis
-Chemical reaction where plants make glucose from sun’s energy
- produces O2 for the planet
Reactants
- Materials that interact
with each other in a
reaction
Photosynthesis Song
Products
- Materials that are created
from the reactants
interacting with one
another
Where does photosynthesis
occur?
Most photosynthesis occurs in the
palisade layer of the leaf because that is
where most of the plant’s
CHLOROPLASTS are located
-Cholor0plasts (tiny green organelles in
plants) trap the sun’s light which is
needed for photosynthesis to take place
-Remove the leaves from a green plant
and the amount of food (glucose) they
produce is reduced dramatically
-Hmm… Do plants make food in winter
then?
Basic Leaf Parts
6. Cuticle
1. Palisade Layer
2. Spongy
Layer
7. Upper
Epidermis
8. vein
3.Air
spaces
4. Guard
Cells
9. Lower
Epidermis
5. Stoma
Leaf Part Definitions
 Cuticle: waxy layer of leaf that prevents excess water loss
 Upper/Lower Epidermis: “skin” of the leaf
 Palisade layer: part of leaf where most chloroplasts are;
glucose production abundant in this layer
 Spongy layer: area of leaf that contains “air spaces” for
gas transport
 Vein: tube that runs through leaf to deliver water and
nutrients
Leaf Part Definitions
 Guard cells: cells on underside of leaf that swell or deflate
in order to allow gas exchange through the stoma
 Guard cells swell or “puff up” to close off the stoma
 They will deflate to allow air through the stoma
 Stomata: stoma, singular; small openings on the
underside of the leaf that allow the exchange of oxygen
and carbon dioxide between the leaf and the outside
environment
STOMATA VIDEO CLIP
Feedback Mechanism in Stomata
Sometimes the stomata must be open to allow
water and gases in for photosynthesis; other
times the stomata must be closed as protection
This is called a feedback mechanism
-If it is really hot and dry outside, the stomata will
be closed to lower water loss
-If it is cooler and humid outside, the stomata will
be open to increase water content
-This allows the plant to maintain homeostasis or
equilibrium
-More or less of either water or gas will affect the
rate of photosynthesis
Cooler
weather
Hot, dry
weather
Photosynthesis Feedback
Mechanism
 What can affect the rate of photosynthesis?
 Low CO2 levels means low photosynthesis rates
 High CO2 levels means higher photosynthesis rates
 Low sunlight levels means low photosynthesis rates
 High sunlight levels means high photosynthesis rates
 Low temperature levels means low photosynthesis rates
 High temperature levels means high photosynthesis rates
Autotrophic Nutrition
 Once a plant makes glucose
from photosynthesis, the plant
still needs to perform another
process to change that glucose
into usable energy called ATP
 This conversion of basic
nutrients like glucose into
energy is called RESPIRATION
 This occurs in the mitochondria
of the plant
 Respiration will be discussed in
detail later on in the year
Heterotrophic Nutrition
 If an organism is a HETEROTROPH, then they must obtain
food from their environment
 Heterotrophs perform three main processes as part of
nutrition:
• Ingestion: act of putting the food source in the oral
cavity of the organism (usually the mouth)
• Digestion: act of internal organs breaking the food
source down in smaller, simpler molecules
• Egestion: the removal of the indigestible food
product in the form of feces
Digestion In-Depth
 Definition
 The breakdown of nutrient molecules (lipids, proteins,
carbohydrates/starches) for use by the cells of the
organism’s body
 Allows these large, complex nutrient molecules to be
broken down into simpler, smaller molecules
 Performed by heterotrophic organisms such as dogs,
cats, humans, pigs, lizards
 Involves two types: mechanical and chemical digestion
Types of Digestion
 Mechanical Digestion
 Breakdown of food into
smaller pieces using force
 Involves the use of muscles
and teeth
 Does not change the nutrient
molecules
 Occurs in the mouth and
stomach only
 Increases the surface area of
food
 Ex. Chewing a piece of steak
with your teeth
 Chemical Digestion
 Breakdown of food into its
most simple, molecular form
 The nutrient is no longer the
original nutrient but rather its
building blocks
 Involves the use of enzymes
and chemicals
 Occurs in the mouth, stomach
and small intestine
 Ex. Protein pieces of steak
breakdown into amino acids
Enzymes
 How can we speed up digestion?
 Use an enzyme!!!
 Enzyme: a catalyst (a material that speeds up a reaction) of a
specific shape; it remains unchanged
• Ex. A Lock and Key
• The key opens the door (door changes; now
open) but the key does not change
• Each key is unique to each lock; a specific shape
Enzymes – A specific shape!
Enzymes – A specific shape!
Want to break down a protein into amino
acids?
- Must have an enzyme that matches SHAPE
with a protein
Want to break down a carbohydrate or
starch into simple sugars?
- Must have an enzyme that matches
SHAPE with a carbohydrate or starch
Want to break down a lipid (fat) into fatty acids
and glycerol?
- Must have an enzyme that matches SHAPE
with a lipid (fat)
What affects the rate of enzymes?
 pH
 The pH (level of acidity or
basicity) can either slow a
reaction down or speed it up
 Each enzyme functions (works)
best at a particular pH
 pH can also denature (change
shape) of enzymes that causes
the enzyme not to work
anymore; shapes no longer fit
together
What affects the rate of enzymes?
 Temperature
 Enzymes work best at a
particular temperature,
depending on the enzyme
 If the temperature is too low,
an enzyme will either be too
slow to start or not work at all
 If the temperature is too high,
the enzyme will denature
(change shape) and the
enzyme will no longer fit onto
the molecule
What affects the rate of a
reaction?
 Concentration of enzyme
 The amount of enzyme and
substrate (what’s being acted
upon by the enzyme) can
affect the rate of an enzyme
 Too little enzyme or too little
substrate slows the reaction
down
 The reaction reaches a point
where it cannot happen any
faster because the enzymes
run out of substrates to pair
with
Human Digestive
System
Order Food Passes Through:
1. Mouth
2. Esophagus
3. Stomach
4. Small intestine
5. Large intestine
6. Rectum
7. Anus
**Notice: Liver, gall bladder and
pancreas not included in the
order because food does not
pass through them
So how does digestion in humans
begin?
 Mechanical digestion begins with
teeth chewing the food
 Chemical digestion
 Starts in the mouth with the
 Chyme: the soupy mixture
(gastric juice) created in the
stomach from the mixture of
the enzymes, acids and food
nutrients
enzyme amylase (in
saliva)breaking down
starches/carbohydrates into simple
sugars
 Proteins begin digesting
 Peristalsis: muscular
chemically in the stomach; pepsin
contractions that push food
(an enzyme specific to protein)
along the gastrointestinal
starts to break the protein down
tract
into amino acids
GASTRIC JUICE VIDEO CLIP
 Muscular contractions in the
stomach continue mechanical
PERISTALSIS VIDEO CLIP
digestion
Digestion in Humans
 Chemical digestion continues in
the small intestine
 The pancreas releases 3 enzymes
into the small intestine that
continue to help breakdown
nutrients
 As the nutrients travel through
the small intestine, these
enzymes continue to break the
food down into a form that can
be absorbed
 Remember, each pancreatic
enzyme can only work with a
specific nutrient of matching
shape
Bile – An emulsifier
 At the same area that the
pancreas secretes enzymes
into the small intestine, the
gall bladder secretes BILE into
the small intestine
 The liver makes the bile; gall
bladder stores it
 Bile “chops up” the fat
molecules into smaller, more
digestible pieces
 Bile breakdown is NOT
chemical digestion
Absorption
 What happens to these nutrients that
have been broken down by enzymes?
 Villi of the small intestine “soak up” or
absorb these nutrients
 The nutrients diffuse (pass through)
into the blood stream
 Once on the “blood bus”, the nutrients
are transported to all the cells of the
body
 The cells use these nutrients to do
chemical processes
Villi: fingerlike projections within
the small intestine that increase
the surface area so more nutrients
can be absorbed
Egestion
 Solid nutrient materials that
cannot be absorbed by the villi
of the small intestine pass into
the large intestine (colon)
 The large intestine (colon)
absorbs excess water
surrounding these larger,
indigestible food nutrients,
creating feces
 Feces then passes through the
rectum and out the anus
 This is called egestion
Digestive Disorders
 Ulcer: a sore/hole in the stomach mucus lining due to
excessive acid production; caused by bacterial infection,
stress, aspirin, ibuprofen and smoking
 Indigestion: painful or uncomfortable feeling in the
stomach typically after eating; usually an indication of an
underlying problem
 Tooth decay: bacterial infection in the mouth; caused
frequently by a lack of brushing and flossing; triggers the
development of cavities
Digestive Disorders
 Anorexia: eating disorder where one refuses to eat or eats
very little; body begins to starve to death from lack of
nutrients
 Bulimia: eating disorder where one consumes food (often
in large amounts) and then vomits the food up to avoid
gaining weight; can include the use of laxatives; causes
severe damage to the esophagus and teeth
Digestive Disorders
 Constipation: difficulty moving food product through the
digestive track due to a lack of fiber and water in the diet;
feces has difficulty exiting the body; can cause intestinal
cramping as well
 Diarrhea: typically caused by a bacterial infection,
condition where feces is extremely loose and runny;
excessive water retained within the stool
Excretion
 When nutrients are digested, and when cells use the
nutrients that are delivered to them by the “blood bus”,
waste products form
 Ex. Think of eating an egg; what is the waste product from
cracking an egg open?
 These waste products must be removed from the body,
otherwise they can become toxic
 The removal of the cell’s wastes is known as excretion
Which waste products must be
removed from the body?
 Carbon dioxide: CO2 is a by-product of making ATP
(energy) during respiration; this gas must be removed
from the body
 Water: excess water is a by-product of making ATP
(energy) during respiration and synthesis; this is removed
to maintain water balance
 Urea and salt: these are both by-products from protein
digestion and must filtered out of the blood stream
Organs of Excretion
 Lungs
 The lungs remove carbon
dioxide from the blood stream
 The carbon dioxide comes
from all the cells of the body
after they make energy (ATP)
 The “blood bus” carries this
carbon dioxide away from
every cell and drops off the
CO2 at the lungs where it is
exhaled
 Excess heat and water also are
excreted at the lungs as well
Organs of Excretion
 Liver
 The liver filters the blood of
certain toxins such as those
associated with drugs, alcohol
and chemical by-products of
various reactions within the
body
 Once the liver filters these by
products, they can then be
transported to the kidneys for
complete excretion from the
body
Organs of Excretion
 Skin
 The skin helps regulate
(control) body balance or
homeostasis by keeping the
body cool
 To maintain body
temperature, the skin excretes
excess heat, water, salt and a
little urea
 The large surface area of the
human body allows the skin to
release excess heat very
effectively
Organs of Excretion
 Kidneys
 The two kidneys filter urea,
salt and other chemicals from
the body
 Tiny filtering units in the
kidneys called nephrons
remove these toxins
 The toxins then flow out of the
kidney through tubes called
ureters
 The ureters deposit the toxins,
now in the form of urine, into
the bladder, where they exit
out through the urethra
Homeostasis in the Kidneys
How does our body maintain water balance if our
kidney’s remove it from our body?
 On hot days, because your
body sweats to cool it down,
expect to produce less urine to
make up for that loss
 On days where you consume
lots of water, expect to urinate
more to maintain proper water
levels
 When your body is
dehydrated, your body
reabsorbs more water through
the kidney, instead of
releasing it in the form of
urine, so expect less urine
production on those days as
well
Excretion Disorders
 Dialysis: this is a PROCEDURE that involves a machine
which filters one’s blood if the kidneys are no longer able
to do so efficiently
 Typically the person goes to the hospital a few times a week
 Blood leaves the body and enters a machine that filters the
toxins out, and then the blood returns to the body
 Jaundice: yellowing of the skin typically caused when
bilirubin, a by-product of broken down red blood cells that
is not properly removed; may be an indication the liver is
not functioning correctly
Excretion Disorders
 Cirrhosis of the liver
 Heavy scarring of the liver due
to repeated damage or disease
 The cell tissue scars over and
can no longer filter the blood
 Jaundice may be a side effect
since the toxins are not being
removed from the blood
efficiently
 Common causes: alcohol and
drug use