The Working Cell: Energy From
Food
Chapter 7
Obtaining Food
All organisms need food for energy.
Autotroph- Makes its own food
(photosynthesis); producers
– Plants, algae
Heterotroph- Cannot make own food;
consumers
– Animals
– Must eat producers or other consumers
How do heterotrophs get energy
from food?
Through Cellular Respiration
– Makes energy for the cell by breaking
down glucose
– Uses oxygen to do this (why we need to
breathe!)
– Energy is in the form of ATP
Food Stores Energy
Energy =The
ability to perform
work.
2 forms:
– Kinetic Energyenergy of motion
Thermal energyrandom molecular
motion (heat)
– Potential Energyenergy that is
stored
Chemical Energyready to do work;
due to arrangement
of atoms
Calories: Units of Energy
Calorie- amount of energy required
to raise the temperature of 1 gram of
water by 1 degree Celsius.
– Tiny number
food)
(too tiny to measure energy in
Energy in food is expressed in
kilocalories
– 1 kcal = 1000 cal
Measuring the Energy Content of a
Peanut
Burning peanut converts its stored
chemical energy into thermal energy,
releasing heat
Measure increase in water temp–
calculate # of calories in a peanut
1 peanut has 5000 calories (5 kcal)
____ °C x ____ mL = ____ cal/
1000 = ___ kcal
Do Cells “Burn” our food?
No!!
Use enzymes to break down organic
molecules through cellular
respiration, thus releasing energy.
Online Activities
www.phsuccessnet.com
Complete online activities 7.1, 7.2,
and ch. 7 prelab questions
Lab: Food as Fuel
Calorimeter: Measures calorie content in
food
We will be burning food to measure their
calorie content.
Remember: 1000 cal = 1 kcal
Remember: Calorie- amount of energy
required to raise the temperature of 1
gram of water by 1 degree Celsius.
Animation
Lab: Food as Fuel
The longer something burns, the
more energy (kcal) it has.
– Proteins/ carbs 4 kcal/g
– Fats 9 kcal/g
ATP
Adenosine Tri-Phosphate
Stores energy
Provides energy for chemical
reactions.
The ATP Cycle
ATP is continuously converted to ADP
as your cells do work.
ATP is “recyclable”
Energy that makes this happen is
from food
Mighty Mitochondria
Mitochondria
makes energy!
Site of cellular
respiration in a cell
Cristae (folds) &
matrix (thick fluid)
Cellular Respiration
Converts energy in food to energy in
ATP
glucose+ oxygen  carbon dioxide
+ water + energy
C6H12O6 + 6O2  6CO2 + 6H2O +
38ATP
Try This…
The atoms in cellular respiration are
merely rearranged by breaking the
bonds.
Using the molecular model kits,
model the process of cellular
respiration.
C6H12O6
+
6O2  6CO2 + 6H2O +
38ATP
Review
6 H2O
Subscript: # of
atoms
Coefficient: # of
molecules
C6H12O6 +
6O2  6CO2 + 6H2O + 36ATP
Lab Review
Lab- we burned food to release
energy (different from our bodies…
we use enzymes to do this)
The more fat, the longer it burned
(what is this telling us?)
What is a calorie? A kilocalorie?
CR Review
Cellular Respiration is making energy
(in the form of ATP) from glucose.
CR takes place in the mitochondria of
cells (“mighty mitochondria”)
Activity with ball-and-stick models
shows that atoms are neither created
nor destroyed in CR, just rearranged
to release energy.
glucose+ oxygen  carbon dioxide
+ water + energy
C6H12O6 + 6O2  6CO2 + 6H2O +
38ATP
Three Stages of CR
1) Glycolysis (in CYTOPLASM of cell)
2) Krebs Cycle (in MITOCHONDRIA
CRISTAE)
3) Electron Transport Chain (in
MITOCHONDRIA MATRIX)
Glycolysis
Glucose
Pyruvic Acid + 2 ATP
2 ATP used to make this happen
Oxygen is NOT needed (anaerobic)
Krebs Cycle
Cristae of mitochondria
Pyruvic Acid
carbonic acid +
CO2 + 2 ATP
Needs Oxygen!
Electron Transport Chain
Matrix of mitochondria
Most of the energy is made here!
Carbonic acid + O2
H2O + 34
ATP
Needs Oxygen!
Is it possible to make ATP without
oxygen??
Fermentation in Human Muscle
Cells
Long Distance Running– muscles
regenerate ATP through CR
Sprint– lungs/blood can’t supply
oxygen fast enough to make enough
ATP!
How does this happen??
FERMENTATION- makes ATP without
using oxygen
Lactic Acid Fermentation
Occurs in muscle cells
But only small amts of ATP made
Glycolysis still occurs
– Glucose
Pyruvic Acid + 2 ATP
Pyruvic acid
CO2 + Lactic acid
Lactic Acid is what makes your
muscles sore after a lot of hard
exercise!
Training
Improves ATP production
Weight lifting & sprinting = increase
glycogen & lactic acid tolerance
Long-distance running= increase
mitochondria & oxygen delivery to
cells
Alcoholic Fermentation
No oxygen present in yeast cell
environment
Ethyl alcohol produced instead of
lactic acid
Pyruvic acid
CO2 + ethyl alcohol
Cellular Respiration Lab
Cell Respiration- converting the
chemical energy of organic molecules
into a form immediately usable by
organisms
What is this chemical energy called?
What is the usable form called?
Cellular Respiration Lab
All organisms, including plants and
animals break down glucose for
energy using oxygen.
Peas undergo CR during germination.
Germination of Peas
What does germination mean?
Cellular Respiration Lab
Today, you will be using the CO2 gas
sensor to measure the rate of CR in
germinating and ungerminating
peas.
Lab Procedure
Do you expect the carbon dioxide
levels to increase or decrease?
Will the rates be the same in the
germinating and ungerminating
peas?
1 ATP
Organisms that make their own food
are called ______________.
1 ATP
Organisms that cannot make their
own food and must obtain energy
from the foods they eat are called
_______________.
2 ATPs
Cell respiration uses oxygen to
convert the chemical energy stored
in organic molecules into
_________.
3 ATPs
Energy is released from ATP when a
____________ is released.
4 ATPs
What is the chemical equation for
cellular respiration?
Hint:
Glucose + oxygen = carbon dioxide +
water + energy
2 ATPs
How many total ATPs are made as a
result of cellular respiration?
3 ATPs
What is the net gain of ATPs as a
result of glycolysis?
3 ATPs
List the steps of cellular respiration
in order.
3 ATP
The Krebs cycle starts with
_____________ and yields carbon
dioxide.
2 ATP
What process is used to make bread
rise?
1 ATP
Is cellular respiration aerobic or
anaerobic?
1 ATP
Is fermentation aerobic or anaerobic?
2 ATP
Where does lactic acid fermentation
take place?
2 ATPs
Where in the cell does glycolysis take
place?
2 ATPs
Where in the cell does the Krebs
cycle take place?
2 ATPs
Where in the cell does the electron
transport chain take place?
3 ATPs
Without oxygen, a cell can make only
_______ ATPs from each glucose
molecule.
3 ATPs
Glysolysis converts glucose into 2
molecules of _____________.
4 ATPs
What is the difference between
kinetic and potential energy?
4 ATPs
What is the definition of a calorie?
1 ATP
# 4 is the __________ of the
mitochondria.
3 ATPs
The device used to measure the
amount of calories in a piece of
popcorn is called a __________.
2 ATPs
There are __________ calories in a
kilocalorie.
2 ATPs
What is the function of ATP?
4 ATPs
What does ATP stand for?
3 ATPs
Most energy made from cellular
respiration comes from this stage.
2 ATPs
What makes your muscles sore after
hard exercise?