Download Name - Humble ISD

Name _____________________________________________________________
Test Date _Tues, 11/16_______
UNIT 6 – THE WORKING CELL
I. CELL BOUNDARIES (pp. 182,183)
A. Cell Wall
Cell walls are the outermost boundary in the cells of _plants___, _fungi___, and _bacteria___. _Protist___ cells
may have cell walls but they are never found in _animal___ cells. The primary function of the cell wall is to provide
_structure and support__. The cell wall does not regulate what _enters and leaves______ the cell.
1. Cell walls of _plants_____ are composed of _cellulose______
2. Cell walls of _fungi_______ are composed of _chitin________
3. Cell walls of _eubacteria___ are composed of _peptidoglycan_____
B. Cell Membrane
Every cell is surrounded by a cell membrane. It helps to maintain _homeostasis______ in the cell by functioning
as a _protective barrier__ between the cell and its environment. The cell membrane is _selectively permeable___
which means it only allows certain things to enter and exit the cell. The cell membrane is also called the
_plasma membrane____. It is not a fixed sheet of molecules, but rather it is a _fluid____ structure composed of three
biomolecule groups, _lipids____, _carbohydrates___, and _proteins______.
1. Lipids – There are two types of lipids that may make up the cell membrane: _phospholipids_______ and
_cholesterol___
a. Phospholipid bilayer – The primary component of all cell membranes is the phospholipid bilayer. Phospholipids
are unique molecules because they are partially _polar____ and partially _non-polar________.
Each phospholipid has 2 _non-polar___ fatty acid tails at one end and a _polar___ phosphate
head on the other end. A cell is surrounded by water and contains a high concentration of water. Water is
_polar___. Polar is attracted to _polar_____, and non-polar is attracted to _non-polar_____ so
the phospholipids form a _bilayer_________ so that the _polar phosphate heads__________ are directed
toward the water inside & outside of the cell and the _non-polar fatty acid tails_______________
are directed toward each other.
b. Cholesterol – Found in the cell membranes of _animal ________ cells only to help stabilize them. This is
important because animal cells _do not have cell walls_____________________________.
Cholesterol is a _non-polar ________ lipid so it is located between the _fatty acid tails________________
of the phospholipid bilayer.
2. Carbohydrates – Serve as “ID tags” to _identify cells__________
3. Proteins – Embedded in the phospholipid bilayer. Serve as _channels_____ and _pumps______ for
transport of specific molecules across the cell membrane.
II. CELL TRANSPORT
(pp. 183-189)
A cell is a working unit and thus, needs to move materials in and out of the cell. There are two transport mechanisms:
A. Passive Transport
Does not require _energy____. Movement of substances from a _high____ concentration to _low______. There are
three types of passive transport:
1. Diffusion – Due to the random movement of molecules in a _liquid_______ or _gas____. Many substances move
across the _cell membrane____ by diffusion.
2. Facilitated Diffusion – Diffusion of _specific molecules______ through a _protein channel_______. Protein
channels provide larger openings for larger molecules like _glucose____________.
3. Osmosis – Diffusion of _water________ through a _selectively permeable membrane________________.
Cells must have a mechanism for counteracting the pressure osmosis can create - otherwise a cell could
_swell and burst_____________ when it comes in contact with a dilute water solution. Cells control this
osmotic pressure in one of three ways:
a. Cell wall - _Physically prevents cell from expanding______
b. Contractile vacuole – Actively _pumps____ water out of cell in single-celled organisms without
_cell walls____________________________
c. Blood – Cells are bathed in blood which is mostly _water____ to equalize osmotic pressure
B. Active Transport
Requires _energy___ in the form of _ATP_____.
1. Protein Pumps - Movement of _ions____ and small molecules against the concentration gradient; that is, from
_low_____ concentration to _high___ concentration.
2. Endocytosis – “_Sucking In_________” Requires movement by cell membrane. In endocytosis, the
cell membrane _surrounds and engulfs_____ particles; for example, _white_________ blood cells
engulfing bacteria and other _pathogens________________
3. Exocytosis – “_Spitting Out____________” Used by cell to release large amounts of material. In
exocytosis, _vesicles___ containing substances move to _cell membrane_____, fuse with it, then _expel__
contents out of the cell; for example, secretion of hormones.
III. CELL METABOLISM (pp. 50-53)
A. _Metabolism____________ is the term used to describe the chemical processes occurring within a living cell that
are necessary for maintenance of life. A key component of metabolism is the use of _enzymes_________________.
Enzymes are _proteins_________ required for virtually every single chemical reaction in an organism; without
enzymes, an organism would not be able to maintain _homeostasis__________.
B. Function of Enzymes - Enzymes trigger chemical reactions in the body by acting as _catalysts_______________.
An enzyme works by lowering the activation energy; that is, the energy required to _get the reaction started______.
C. Characteristics of Enzymes
1. Enzymes work best within a narrow _pH___ and _temperature______ range.
2. Enzymes do not make a reaction happen that couldn’t happen on its own; they simply make
the reaction occur much _faster________.
3. Enzymes are not _changed____ or _used up__________ in the reaction. The same enzyme
may be used over and over again.
4. Enzymes are _substrate-specific____________. A substrate is the _reactant__________
Enzymes are substrate-specific because of their _shape_________. The substrate fits into a portion
of the enzyme called the _active site_____. This fit between the active site of the enzyme and
the substrate allows enzymes to be specific for a certain type of reaction.
IV. CELL ENERGY (pp. 202, 203, 221-225)
Energy is the _ability to do work______________. We obtain energy from _food______, but most energy
originally comes from the _sun_____. Plants are able to capture the sun’s energy and use it to produce glucose,
_C6 H12 O6______. This process, known as _photosynthesis_______, occurs in the _chloroplasts_________
of plant cells. The equation for photosynthesis is:
_CO2 + H2O + energy → C6 H12 O6 + O2_____________
A. Chemical Energy
The chemical energy in food (and all molecules) is stored in the _chemical bonds_____________. This is
_potential______ energy. When the bonds are broken and the _electrons_______ are released, some energy
is lost as _heat________, but a percentage of the potential energy can be converted to useable energy in the form
of _ATP___. Food molecules cannot be used as a direct energy source for the cell because _the amoung of energy
released would be wasteful and destructive______________________
B. ATP
_Adenosine TriPhosphate____ is a _nucleotide composed of:
 Nitrogen base - _adenine_______
 5-Carbon sugar - _ribose______
 _3__ phosphate groups
Energy is stored in _phosphate – phosphate bonds_____. ATP works like a rechargeable battery.
Cells are able to use and recycle ATP by breaking off or adding a _phosphate_ group.
1. Energy can be used by the cell when a phosphate bond is _broken________ and _ATP____ is
converted to _ADP______ - _adenosine diphosphate_____________
2. Energy is stored; that is, ATP is “recharged” by _adding_____ a phosphate group to _ADP___ to
make _ATP_____.
C. Cellular Respiration - _Aerobic______ Energy Production (pp. 221-223, 226-229)
Cellular respiration is the breakdown of _glucose________ in the presence of _oxygen___ to “make”
_ATP_____. In _eukaryotic_______ cells, this process occurs in the _mitochondria___________.
The equation for cellular respiration is
_ C6 H12 O6 + O2 → CO2 + H2O + energy (ATP)____________
In humans,
1. The oxygen required for cellular respiration is _inhaled_____ into the_lungs___, _diffuses _ into the _blood____,
and is delivered to the _mitochondria________ of the body cells by _red blood cells_______. We exhale the waste
products from cellular respiration, _ CO2_____ and _ H2O _____.
2. The glucose comes from the _digestion____ of _food_______. The glucose is absorbed into
the _blood___ moves into body cells via _facilitated diffusion___.
**TOTAL ATP GAIN IN CELLULAR RESPIRATION =
36
ATP per MOLECULE OF GLUCOSE **
D. Fermentation - _Anaerobic_____ Energy Production
If oxygen is not available, some types of cells have a back-up mechanism for glucose metabolism called
_fermentation___. The fermentation pathway only produces _2____ ATP per molecule of _glucose______.
The two most common fermentation pathways used by cells are:
1. Lactic Acid Fermentation
a. Human Muscle Cells – Occurs when demand on muscles exceeds supply of oxygen. As lactic acid builds up in
the muscle cells, it is felt as _pain and fatigue_________. This is referred to as _oxygen debt__________
As activity slows, and oxygen is re-supplied, the muscle cells switch back to _cellular respiration________ and the
lactic acid is sent to the _liver_________ to be broken down.
b. Bacteria – There are some types of bacteria that carry out lactic acid fermentation in _anaerobic______
conditions. This is utilized by the dairy industry to produce _yogurt_____ and _cheese___.
2. Alcoholic Fermentation - When oxygen supplies are depleted, _yeast___ switch to alcoholic fermentation.
This process is used commercially for _brewing and baking____
**TOTAL ATP GAIN IN FERMENTATION =
2 ATP per MOLECULE OF GLUCOSE **