Chapter 5 Homeostasis and Cell...
Transcript of Chapter 5 Homeostasis and Cell...
Palabra Palooza!
• Role #1: The Definer says:
– The word __________ can be
explained as _____________
• Role #2: The Re-stater says:
– Then I understand
__(word)____ to mean
_____________
– Words:
• Passive
transport
• Diffusion
• Equilibrium
• Osmosis
• Facilitated
diffusion
Human Matching
1. concentration of molecules is the same
throughout the space
2. diffusion of substances across a cell
membrane with the aid of carrier proteins
3. movement of substances across a cell
membrane without the use of energy
4. the diffusion of water molecules from an
area of higher concentration to an area of
lower concentration
5. movement of molecules from an area of
higher concentration to an area of lower
concentration
___Passive
transport
___Diffusion
___Equilibrium
___Osmosis
___Facilitated
diffusion
What is homeostasis?
Homeostasis is the ability to maintain
normal internal conditions. This means
maintain a state of balance in living
things.
Cells must maintain homeostasis
What structure does a cell
have to help it maintain
homeostasis? • Cells are enclosed in a phospholipid
bilayer called a cell (plasma) membrane
that regulates their interactions with
their surrounding environment.
• A cell membrane has a specific
structure that allows it to be semi-
permeable.
What is the cell membrane’s
structure and function?
1. Semi/Selectively permeable (controls
what substances enters and leaves the
cell)
2. Helps organisms maintain homeostasis
What is selectively
permeable?
• Selectively permeable means that the
membrane will allow some substances
to pass through and will not allow other
substances to pass through.
What is permeable and
impermeable?
If a membrane allows a substance to pass
through, it is said to be permeable to
that substance.
If a membrane does not allow a
substance to pass through, it is said to
be impermeable to that substance.
How does a cell maintain
homeostasis?
Through the movement of different
molecules through the cell membrane
by:
1. Passive transport
or
2. Active transport
2. What is passive
transport?
• The movement of
substances across
a cell membrane
without the use of
energy by the cell.
3. What is diffusion?
• The simplest type of passive transport.
• The movement of molecules from an area of higher concentration to an area of lower concentration.
• Molecules move on their own kinetic energy.
Examples: When you add
a sugar cube to water
Aroma (smell) of microwave popcorn
What does it mean by
kinetic energy?
• Molecules are in constant motion because they have kinetic energy
• Molecules move randomly in a straight line until they hit another molecule, then bounce off and move in the opposite direction.
• Molecules have the tendency to move from high to low concentration.
4. What is equilibrium?
• When the concentration of molecules of
a substance is the same throughout a
space.
• Even at equilibrium there is a random
movement of molecules.
CHECK IT
Partner #1: Explain the structure of a cell
membrane and the term semi-
permeable.
Sentence starter:
The cell membrane is made up of _____
Semi or selectively permeable means ___
CHECK IT
Partner #2: Describe the term diffusion.
Be sure to include the term “passive
transport” in your answer.
Sentence Starter:
Diffusion is ________
5. What is a solution?
• A solution is composed of a solute dissolved in a solvent.
• Example: Salt water – Salt is the solute
– Water is the solvent
• In the case of cells, the solutes are organic* and inorganic compounds, and water is the solvent. – *Carbohydrates, Proteins, Lipids
6. What is osmosis?
• Osmosis is the movement of water across a cell membrane from an area of higher concentration to an area of lower concentration.
****Because water is moving from an area of higher concentration to an area of lower concentration, osmosis does not require cells to expend energy.
*****Therefore, osmosis is a type of passive transport!!!!!
7. What determines the
direction of the water?
• The relative concentration of water and
solute on the two sides of the cell
membrane.
8. Some Definitions…
• Hypertonic-higher concentration of solutes
• Isotonic-even concentration of solutes
• Hypotonic-lower concentration of solutes
• In living systems, the point of reference
is always the cytoplasm, so the prefix
hypo- means that the extracellular fluid
has a lower concentration of solutes
than the cell cytoplasm.
• It also means that the extracellular fluid
has a higher concentration of water in
the solution than does the cell. In this
situation, water will follow its
concentration gradient and enter the
cell, causing the cell to expand.
Source: Boundless. “Water
8. Some Definitions… The outside
fluid is…
If the fluid
outside the
cell has…
Water
diffuses…
Effect on
the cell…
Isotonic Equal conc.
of H2O and
solutes
Into & out of
cell at the
same
rate
Cell is
normal
(shape and
size)
Hypotonic Lower conc.
of solutes
(higher conc.
of water)
Into the cell Cell will swell
and burst
(cytolysis)
Hypertonic Higher conc.
of solutes
(lower conc.
of water)
Out of the
cell
Cell will
shrink
(plasmolysis
or crenation)
9. What happens to the cells of
a freshwater fish when it is in a
saltwater tank?
• Fish-- Animal Cells No Cell Walls
• Salt
9. What happens to the cells of
a freshwater fish when it is in a
saltwater tank?
• Salt • Outside
solution is
hypertonic
• Plasmolysis
occurs
H2O leaves fish’s cells and fish will die
10. What happens to the cells
of a saltwater fish when it is in
a freshwater tank?
• Fish-- Animal Cells No Cell Walls
• Salt
10. What happens to the cells
of a saltwater fish when it is in
a freshwater tank?
• Salt
• Outside
solution is
hypotonic
• Cytolysis
occurs
H2O enters fish’s cells and fish will die
11. How do plant cells deal
with osmosis?
• Plant cells have cell wall and most live a
hypotonic environment. This moves water
into the cells by osmosis.
• These cells swell as they fill with water until
the cell membrane is pressed against the
inside of the cell wall. The water exerts of
pressure against the cell wall called turgor
pressure.
11. How do plant cells deal
with osmosis?
• In a hypertonic environment, water leaves the cells through osmosis. As the water leaves the central water vacuole, the cells shrink away from the cell walls, and turgor pressure is lost.
• This condition is called plasmolysis, and is the reason that plants wilt if they don’t receive enough water.
12. How do unicellular
organisms deal with osmosis? • Because most of them live in a
hypotonic environment, water is constantly entering the cells, so they must rid themselves of the excess water.
• Some of them, such as the paramecia have structures called contractile vacuole which remove the excess water by pumping it out of the cell.
• https://www.youtube.com/watch?v=vk5NFSvp8lY
14. What is facilitated
diffusion?
• Another type of passive transport in
which molecules that cannot readily
diffuse across a membrane are assisted
by carrier proteins in the membrane. » Example: glucose diffusing across a cell
membrane through the protein
https://www.youtube.com/watch
?v=mzo_B5F7pk4
Check your knowledge
We have talked about three types of
passive transport. Take a minute to
quietly look through your notes and
refresh you memory on the three types
of passive transport.
Circle the three types of passive
transport in your notes!!!
Check your knowledge With your table partner discuss the
following:
Partner 1: Explain the term passive
transport.
Passive transport is the movement of
molecules from and area of ______
Partner 2: Explain diffusion. What types of
substances diffuse through our cells.
Diffusion is the movement of ________ from
an area of______
Check your knowledge
Partner 1. Explain osmosis. What
substance is moved in our cells through
osmosis?
Osmosis is the movement of ________
from an area of______
Partner 2. Explain facilitated diffusion.
What substance is moved in our cells
using facilitated diffusion.
Facilitated Diffusion is the movement of
________ from an area of______
15. What is active
transport?
• The movement of substances, usually
across a cell membrane, against (up) a
concentration gradient which requires
cells to use energy.
16. What does “against” a
concentration gradient mean?
• When cells move substances from an
area of lower concentration to an area
of higher concentration.
17. How are carrier proteins
involved in active transport?
• Carrier proteins in animal cells are involved in
an active transport process called the
sodium-potassium pump. In humans this
process occurs in muscle cells and liver cells.
Cells have to expend energy to pump
Potassium (K+) ions into the cells and to
pump Sodium (Na+) ions out of cells.
https://www.youtube.com/watch
?v=6R2-AFcJrhs
18. How do macromolecules that
are too large to pass through the
cell membrane by the other
process get in and out of the
cells?
• 1) Endocytosis - the process by which
cells ingest external fluid,
macromolecules, and large particles,
including other cells.
Endocytosis
• Two types:
a) Pinocytosis -involves the transport of solutes or fluids
b) Phagocytosis -involves the transport of large solid particles or whole cells.
Example: White blood cells engulfing bacteria or amoeba engulfing a paramecium
• 2) Exocytosis- the process by which a
substance is released from the cell
through a vesicle that transports the
substance to the cell surface and then
fuses with the membrane to let the
substance out of the cell.
• Cells use exocytosis to release large
molecules such as proteins, waste
products, or toxins that would damage
the cell if they were released within the
cytosol. https://www.youtube.com/watch?v=r2PiumV8
KEY