Chapter 23- How
Cells Work
BIG IDEA: Cells perform a
wide variety of tasks in order
to live and carry out their
functions.
23.1 How Things Get in and out
of Cells
Cells need to be able to receive nutrients, and export wastes.
Diffusion is the process by which molecules move from an area
of higher to lower concentration.
Called “moving down a concentration gradient”
Diffusion does NOT require cellular energy
Ex: food coloring in water
Osmosis is the diffusion of water.
Facilitated diffusion- doesn’t require cell energy
Most molecules cannot move across the
membrane on their own. Need transport
proteins
Active transport requires cellular energy!
Endocytosis
Part of the cell
membrane pinches in
to form a vesicle that
brings in nutrients.
Exocytosis
Vesicle inside the cell
fuses w/ membrane,
and releases it’s
contents outside of the
cell.
23.2 How Cells Reproduce
Mitosis is a type of cell division in which
1 cell divides into 2. Resulting cells are
genetically identical to the original cell.
Cell Cycle:
1.Gap 1(G1)- Chromosomes condense,
prepare for cell division.
2. Synthesis- chromosomes replicate
3. Gap 2(G2)- Builds machinery for cell division
4. Mitosis and Cytokinesis: cell divides
completely
Phases of Mitosis:(PMAT)
Prophase: nuclear membrane breaks down,
chromosomes condense
Metaphase: Chromosomes line up in middle
Anaphase: sister chromatids separate
Telophase: New nuclear membrane forms
around the product:2 cells
-Cytokinesis= division of cells completely
23.3 Enzymes and the Chemical
Reactions in cells
Exothermic- chemical reactions that release heat
Endothermic- chemical reactions that absorb heat
Integrated Science: Chemistry
Substrate: where reactants are brought together to react
Enzyme-substrate complex: the reactants of enzymecatalyzed
reactions
Like a “lock and key” they must fit together completely
Temperature, pH, and other factors can
affect the activity of enzymes
Enzymes are biological catalysts (speed up reactions).
-Enzymes lower the energy required to start a reaction.
Integrated Science: Chemistry
Adenosine triphosphate (
ATP) is cellular energy
When the 3rd phosphate group is removed
(making adenosine diphosphate [ADP]) cells
get energy
ATP in the Sodium-Potassium
pump
This pump uses active transport to pump in
sodium and potassium out.
-Important in how our brain cells work
23.4 Photosynthesis
All life on Earth ultimately depends on
photosynthesis for energy
-Uses carbon dioxide, water, and sunlight to
produce oxygen and glucose (sugar)
23.5 How Cells get Energy
When chemical bonds break to make
glucose energy is released.
-When it uses oxygen= cellular respiration
Steps of cellular respiration:
1. Glycolysis 2. Kreb’s Cycle
3. Electron transport chain
Fermentation
When cells use energy without oxygen= anaerobic
-Important in making wine and bread.
- How our muscles allow us to continue to exercise
without oxygen
(Lactic acid is produced, and it is the burn you feel
during a workout)