Unit A
Chapter 2
HOW CELLS
FUNCTION
2.1 Chemical Reactions take place inside cells
•All matter in the universe – both
living and nonliving – can be
broken down into basic
substances called elements
 Element – substance
that consists of only
atoms of one type
 Example: oxygen
2.1 Chemical Reactions take place inside cells
 Molecule – group of atoms held together by bonds
Oxygen
2.1 Chemical Reactions take place inside cells
 Compound –
substance made
of two or more
different types of
atoms
 Example – Water
H2O
2.1 Chemical Reactions take place inside cells
 Most cell activities involve atoms and
molecules interacting
 Chemical reaction –atoms are rearranged
and chemical bonds are broken and formed
2.1 Chemical Reactions take place inside cells
2.1 Chemical Reactions take place inside cells
2.1 Chemical Reactions take place inside cells
 Energy is released
when bonds break
 Energy is needed
to form bonds
between atoms
Therefore, energy that cells use for life
activities is chemical energy
2.1 Chemical Reactions take place inside cells
 There are 4 main types of large molecules in living
things
• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
**Are made up of
smaller parts called
subunits
**All contain
carbon atoms
2.1 Chemical Reactions take place inside cells
It’s time to learn more
about large compounds
2.1 Chemical Reactions take place inside cells
 All chemical reactions in a cell take place in water
 About 70% of your body is water
Water is also
present
outside of the
cell
 Water makes
up about 2/3
of every cell
What prevents the water from inside the cell from
mixing with water from outside of the cell?
2.1 Chemical Reactions take place inside cells
 Cell membrane -
Made of a special type of lipid that is polar
Tail – water
hating
Head – water
loving
The cell membrane acts as a boundary.
It keeps outside water out and the cell’s
water in.
2.2
Cells Capture and
Release Energy
2.2 Cells Capture and Release Energy
 Cells need energy
 Plant cells – from sunlight
Animal cells – from food
2.2 Cells Capture and Release Energy
Photosynthesis
 Process that plant cells use to change
energy from sunlight into chemical
energy
 Takes place in the chloroplasts
•chloroplasts have chlorophyll –
a light absorbing pigment that traps
energy in sunlight
2.2 Cells Capture and Release Energy
Photosynthesis
 Starting materials
 light energy
 carbon dioxide
 Water
H2O
CO2
2.2 Cells Capture and Release Energy
Photosynthesis
 Process
 Chlorophyll captures energy
from sunlight
CO2
 Energy is used to change
H2O
carbon dioxide and water into
new products
2.2 Cells Capture and Release Energy
Photosynthesis
 Products
 glucose C6H12O6 - supplies
energy
 oxygen O2 - most is released
as waste product
into the air
2.2 Cells Capture and Release Energy
Photosynthesis
water
6H2O
+
carbon
dioxide
6CO2
+
light
energy
glucose
C6H12O6
+
Oxygen
6O2
2.2 Cells Capture and Release Energy
 Some of the glucose is linked with
other glucose and stored as starch
 Plants can break this down later for
energy
 Cells break the bonds of sugar
molecules to release the chemical
energy and get a burst of energy
2.2 Cells Capture and Release Energy
 Cells need to release energy
 Two ways cells release energy:
•cellular respiration
•fermentation
2.2 Cells Capture and Release Energy
Cellular Respiration
 Provides most of the energy
used by cells in your body
 Plant and Animal Cells use oxygen to
release energy stored in sugars
 Takes place in the
mitochondria
2.2 Cells Capture and Release Energy
Cellular Respiration
 Starting materials
 glucose C6H12O6
 oxygen
O2
2.2 Cells Capture and Release Energy
Cellular Respiration
 Process
 Glucose is broken down into
smaller molecules while in the
cytoplasm
 This releases a small amount
of energy
2.2 Cells Capture and Release Energy
Cellular Respiration
 Process
 Molecules move into the
mitochondria while oxygen
enters the mitochondria
 The smaller molecules are
broken down even further
2.2 Cells Capture and Release Energy
Cellular Respiration
 Process
 Energy is released with
hydrogen atoms that combine
with the oxygen atoms to
make water
2.2 Cells Capture and Release Energy
Cellular Respiration
 Products
 energy
 carbon dioxide
 Water
H2O
CO2
2.2 Cells Capture and Release Energy
Cellular Respiration
 Energy from cellular respiration is:
 transferred to other molecules
or
 released as heat
 Carbon dioxide is released by the cell
2.2 Cells Capture and Release Energy
Cellular Respiration
glucose
C6H12O6
+
Oxygen
6O2
energy
+
carbon
dioxide
6CO2
+
water
6H2O
2.2 Cells Capture and Release Energy
Fermentation
 Process by which cells release
energy without oxygen
 Foods that involve fermentation:
 bread
 yogurt
 cheese
2.2 Cells Capture and Release Energy
Fermentation
 Starts with the small molecules
made from sugars at the beginning
of cellular respiration
 If there is no oxygen, cellular
respiration cannot continue
 The molecules stay in the cytoplasm,
where fermentation occurs
2.2 Cells Capture and Release Energy
Fermentation
 Two types of fermentation:
 Alcoholic fermentation:
 Cell releases alcohol, carbon dioxide,
and a small amount of energy
C6H12O6
2C2H5OH + 2CO2
2.2 Cells Capture and Release Energy
Fermentation
 Two types of fermentation:
 Lactic acid fermentation:
 Cell releases lactic acid and a small
amount of energy
C6H12O6
CH3CHOHCOOH
2.3 Materials move across cell membranes
Passive Transport
 Materials move in and out of cells
without the use of energy
 Types of passive transport:
 diffusion
 osmosis
2.3 Materials move across cell membranes
Diffusion
 Process by which molecules move
from areas of high concentration to
areas of low concentration
Over
time
 Concentration – the number of
particles in a specific volume
2.3 Materials move across cell membranes
Diffusion
 Transports materials in and out of
cells
 Used to carry out cell functions
 Diffusion animation
2.3 Materials move across cell membranes
Osmosis
 Diffusion of water across a cell
membrane
2.3 Materials move across cell membranes
Not all materials can move in and
out of a cell by diffusion
 Sometimes materials move against
concentration, which requires
energy
2.3 Materials move across cell membranes
Active Transport
 Using energy to move materials
through a membrane
 Used for many life functions
 Example:
marine iguana
removing
excess salt
2.3 Materials move across cell membranes
Types of Active Transport
 exocytosis
 endocytosis
2.3 Materials move across cell membranes
Exocytosis
 Cells use energy to move large
materials out of the cell
 The large material is enclosed by a
membrane and removed from the cell
2.3 Materials move across cell membranes
Endocytosis
 Cells use energy to move large
materials into the cell
 The large material is captured within
a pocket of the cell membrane
 The cell membrane folds inward,
creating a package that breaks off
and moves into the cell