Download Unit 2 The Chemistry of Life

Seventh Grade
1
Moving Cellular Material
A. Passive Transport
1. A cell membrane is semipermeable,
which means that it allows only
certain substances to enter and leave a
cell.
2. Passive transport is the movement of
substances through a cell membrane
without using the cell’s energy.
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B. Diffusion
1. Diffusion is the movement of
substances from an area of higher
concentration to an area of lower
concentration.
2. Usually diffusion continues through a
membrane until the concentration of a
substance is the same on both sides of
the membrane.
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C. Osmosis-The Diffusion of Water
1. Osmosis is the diffusion of water
molecules only through a membrane.
2. If the concentration of water in the air
surrounding a plant is less than the
concentration of water inside the
plant’s vacuoles, water will diffuse
into the air until the concentrations
are equal.
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3. Facilitated diffusion allows molecules
to pass through a cell membrane using
transport proteins.
a. Carrier proteins carry molecules
through the cell membrane.
b. Channel proteins allow ions to pass
through the cell membrane.
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D. Active transport
1. Active transport uses cell’s energy
to move substances through a cell
membrane.
2. Active transport moves substances
from areas of lower concentration
to areas of higher concentration.
3. A cell uses endocytosis to take in a
substance by surrounding it with
the cell membrane.
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3. A cell uses endocytosis to take in a
substance by surrounding it with
the cell membrane.
4. A cell’s vesicles release their
contents outside the cell during
exocytosis.
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E. Cell Size and Transport
1. For a cell to survive, its surface
area must be large compared to its
volume.
2. As a cell grows, its volume
increases faster than its surface
area.
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Question: How do substances move
into and out of cells?
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Substances can move into and out of
cells by diffusion, osmosis, facilitated
diffusion, endocytosis, and exocytosis
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Cells and Energy
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Cells and Energy
A. Cellular respiration
1. All living things need energy to
survive.
2. Cellular respiration is a series of
chemical reactions that convert the
energy in food molecules into a
usable form of energy called ATP.
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3. The first step of cellular respiration,
called glycolysis, occurs in the
cytoplasm of all cells.
4. During glycolysis glucose, a sugar, is
broken into smaller molecules.
5. The second step of cellular
respiration occurs in the mitochondria
of eukaryotic cells. This step
requires oxygen.
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6. During the second step of cellular
respiration, the smaller molecules
made during glycolysis are broken
down. Large amounts of usable
energy, called ATP, are produced.
7. Water and carbon dioxide (CO2) are
two waste products that are given off
during the second step of cellular
respiration.
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C. Fermentation
1. Eukaryotic and prokaryotic cells use
fermentation to obtain energy form food
when oxygen levels are low.
2. Fermentation occurs in a cell’s
cytoplasm.
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3. Lactic-acid fermentation converts
glucose into ATP and a waste product
called lactic acid.
4. Some types of bacteria and yeast make
ATP during alcohol fermentation. This
process produces ethanol and CO2.
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C. Photosynthesis
1. Plants and some unicellular
organisms obtain energy from light.
2. Photosynthesis is a series of
chemical reactions that convert light
energy, water, and CO2 into glucose
and oxygen.
3. In plants, light energy is absorbed
by pigments such as chlorophyll.
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4. The chemical reactions of
photosynthesis occur in chloroplasts,
the organelles in plant cells that
convert light energy into food.
5. Photosynthesis uses CO2 that is
released during cellular respiration to
make food energy and release oxygen.
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6. When an organism eats plant
material, it takes in food energy. An
organism’s cells use oxygen released
during photosynthesis.
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Question:
How are cellular respiration and
photosynthesis related?
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Photosynthesis uses light energy and CO2
that is released during cellular respiration
to make food energy and release oxygen.
When an organism eats plant material, it
takes in food energy. An organism’s cells
use oxygen released during
photosynthesis and converts the food
energy into usable energy through cellular
respiration.
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