Transcript Energy For Life - Salisbury Composite High School

Energy For Life
Chapter 7
Nature's Energy
Conversions
 Life on Earth could not exist without
plants
 Without oxygen, which comes from
plants, oxygen-breathing animals would
not exist
 BUT, without oxygen-breathing animals,
plants would not exist either!!
Plant’s and energy
conversion
 Plants are like a solar cell, they convert energy
from the sun into chemical potential energy
 The cells of the green plants have special parts that
capture the energy from the sun and convert it into
energy the plant can use. The plant then uses that
energy to produce oxygen and food molecules
(chemical potential energy) which are used by animals,
this process is called PHOTOSYNTHESIS
The cells of the plant
 Green plants have
cells called
chloroplasts, inside
each of the
chloroplasts there is
chlorophyll pigment,
this is where
photosynthesis takes
place.
 The photosynthesis
rxn is:
CO2 + water + light energy  glucose (sugar) +
oxygen
Glucose
 Glucose is a simple sugar
 Glucose is a carbohydrate that is rich in
chemical potential energy that when eaten by
animals is converted to a usable energy
 Glucose is the main source of energy for all
cells. Cells can also get energy from proteins,
fats, and other food molecules.
 Out human bodies use carbohydrate as a
source of ENERGY
Cell Respiration
 Cellular respiration is a process used by all
plant and animal cells to obtain energy from
food
 When we eat, we break down food into a
usable from of energy which drive most
reactions in our body
 Cell Respiration is the opposite of
photosynthesis!
 The cell respiration rxn is:
Glucose + oxygen  CO2 + water + energy
 Cell respiration in the
human cell is like a car,
both need oxygen and
fuel to operate and they
both release carbon
dioxide and water
 Cell respiration in
animals takes place in
specialized cells called
mitochondria
 In order to operate, an
organism must eat food
(glucose) to get energy.
2 Energy Conversions:
 In plants:
Input energy  converter  output energy
Solar energy 
chloroplasts 
chemical potential
(glucose)
In Animals:
Input energy  converter  output energy
Chemical potential  mitochondria  muscular activity
(kinetic energy)
Energy Conversions: Plants to
Animals
Usually only 10% of the energy
 Energy is being converted
from one from to another all
of the time
 Most of the time, energy is
being lost as waste, either
as heat (thermal energy),
sound, or poop. Thus, when
you do physical activity, a
ton-of-energy is lost to cool
the body down or as heat.
 As you move up a food
pyramid, there are less and
less organisms due to less
energy being available to
them.
at one level is passed on to the
next level
0.1J
1J
10J
100J
1000J
The need for energy
 Energy in organisms is usually used for
movement, growth, reproduction and to keep
the body temperature constant.
 The major use of energy in animals is for
HOMEOSTASIS, which is balance. The body is
like a thermostat, when it is too cold, the body
turns up the heat, if the body is too warm, the
body turns down the heat. The body likes to be
at equilibrium at all times!
 The human body does a couple
things to adjust it’s temperature, they
are:
 Blood vessels move close to
the skin surface to increase
the rate of heat transfer
 Perspiration: to cool the
body off you sweat. Some
animals pant
 Shivering: warms the body
up by causing the muscles to
burn more energy
 Blood vessels can constrict
to prevent blood to the limbs
and thus heat loss.
Sources of Energy for
Animals
 Food is the fuel that gives us energy to keep warm, be
active, and stay alive.
 Recall: The main source of energy is carbohydrates, which
comes from plants due to photosynthesis
 3 sources of energy:
1) Carbohydrates:
-Glucose is the main simple carb, it is broken down in the
body to produce energy, or it is stored as glycogen.
Glycogen is stored in the liver and muscles to be used later.
-Experts say that 55-65% of our diet should be carbs
-Carbo Loading is when athletes take in extra carbs so
that they can store them
-Food rich in carbs: pasta, breads, potatoes
 2) Fats:
 Fat is need for insulation, to store energy,
and to make energy
 Once carbos run low, the body then use fats
as a backup energy source.
 However, fats can produce about 2X the
amount of energy as carbs!
 2 types of fats exist:
 1) Saturates: these come from animal fat and
oils and cause heart disease
 2) Unsaturated fats: come from vegetable oils
and these reduce heart disease
-We should try to eat only unsaturated fats and fats
 3) Proteins:
 Proteins contain about the same amount of energy
as carbs, but its harder for the body to break down
proteins, thus it proteins take longer to produce
energy
 Proteins is a poor source of energy, but are needed
in many other body processes, such as: build body
tissue and muscles, growth and repair of the body
 Proteins are ‘building blocks’ of our body: by eating
meats we take in a lot of proteins
Human Energy For Change
 Our need for energy changes
as we grow older
 As a fetus and infant, most of
the energy is needed for
growth and development.
When the baby is in the womb,
an umbilical cord is used to
pass minerals, nutrients, and
other chemicals from the
mother to the baby.
 As people age, their metabolic
needs change, when kids go
through puberty their
metabolism increase so that
enough energy is available to
increase in mass and height.
What affects metabolism
 There are many factors that affect
metabolism(=rate at which the human body
uses energy) they are:
 1) Age: younger people have higher metabolism
 2) Time of day: metabolism is higher in the morning,
and peaks around 10am.
 3) Exercise: Activity increases metabolism
 4) Level of fitness: athletes have high metabolism
One way to avoid gaining weight is to stay active, not
just reduce food intake!!