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Animal Cell
Plant Cell
Journey through the cell
• https://www.youtube.com/watch?v=VJEfeXU3f24
• Plasma (cell) membrane – the membrane at the boundary of every cell. – It is selectively permeable – meaning that it
controls the substances entering and exiting the cell.
• The plasma membrane is made up of a phospholipid bilayer.
• The phospholipid bilayer is made up of single units called phospholipids.
• A phospholipid is made up of:– A polar hydrophilic
head (polar head - phosphate group and glycerol)
– A non-polar hydrophobic tail
(2 chains of fatty acids)
• The non-polar, hydrophobic tails position themselves in the middle region of the bilayer. The polar, hydrophilic heads positions facing outwards and interacts with the water.
OUTSIDE – EXTRACELLULAR MATRIX
INSIDE – CYTOPLASM
PHOSPHOLIPIDBILAYER
Fluid Mosaic Model
• The fluid mosaic model describes the plasma membrane of animal cells, in which the membrane is a fluid structure with a “mosaic” of various proteins embedded or attached.
• Integral proteins – are protein structures that completely spans the hydrophobic region of the plasma membrane.
• Peripheral proteins – are protein structures that are attached to the surface of the plasma membrane and not embedded in the lipid bilayer.
• Cells must maintain an internal balance of substances, and requires the ability to eliminate toxins and waste products produced within the cell.
• This can be done in two processes:1) Passive Transport2) Active Transport
Passive Transport
• Does not require energy for transport of materials into and out of the cell.
• Examples: – Simple Diffusion–Osmosis and – Facilitated diffusion
• Solutes will move in the direction of higher concentration to lower concentration of a particular solute.
• Bidirectional and slow
Simple Diffusion• Doesn’t require energy• Moves high to low concentration• Example: Oxygen diffusing into a cell and
carbon dioxide diffusing out.
• Brownian motion – the random motion of molecules.
• https://www.youtube.com/watch?v=UC0bKzgQU9g
• 1:35 – 2:12
Facilitated Diffusion • Doesn’t require energy• Uses transport proteins to move from high
to low concentration• Examples: Glucose or amino acids moving
from blood into a cell.
• Osmosis - diffusion of water across the plasma membrane down its concentration gradient
• Moves from HIGH water potential (low solute) to LOW water potential (high solute)
Diffusion of H2O Across A Membrane
High H2O potentialLow solute concentration
Low H2O potentialHigh solute concentration
Aquaporins• Water Channels• Protein pores used during OSMOSIS
WATERMOLECULES
Cell in Isotonic Solution
CELL
10% NaCL90% H2O
10% NaCL
90% H2O
What is the direction of water movement?The cell is at _______________.equilibrium
ENVIRONMENT
NO NET MOVEMENT
Cell in Hypotonic Solution
CELL
10% NaCL90% H2O
20% NaCL
80% H2O
What is the direction of water movement?
Cell in Hypertonic Solution
CELL
15% NaCL85% H2O
5% NaCL95% H2O
What is the direction of water movement?
ENVIRONMENT
Video
• https://www.youtube.com/watch?v=w3_8FSrqc-I
Cells in Solutions
Isotonic Solution
NO NET MOVEMENT OF
H2O (equal amounts entering
& leaving)
Hypotonic Solution
CYTOLYSIS
Hypertonic Solution
PLASMOLYSIS
Cytolysis & Plasmolysis
Cytolysis Plasmolysis
Osmosis in Red Blood Cells
Isotonic Hypotonic
Hypertonic
What Happens to Blood Cells?
hypotonic hypertonic isotonic
hypertonic isotonic hypotonic
Active Transport
Requires energy or ATP
Moves materials from LOW to HIGH concentration
AGAINST concentration gradient
• Substances moving via active transport includes:– substances that are too large – substances that cannot dissolve in the lipid-
bilayer – substances that are unable to move down
its concentration gradient.
What is ATP?
• Adenosine Triphosphate
Active transport
Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients.
Called Na+-K+ Pump
Sodium-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped out; creates a membrane
potential
Crash Course – In Da Club• https://
www.youtube.com/watch?v=dPKvHrD1eS4
Compare and Contrast
• List as many things that are similar and as many things that are different about passive transport and active transport.
Quiz… Just for Fun
Question 1• In which type of transport are there carrier
proteins?
– Passive transport (facilitated diffusion, osmosis) and active transport
Quiz… Just for Fun
Question 2• Which type of transport is non-specific?
– Simple diffusion
Quiz… Just for Fun
Question 3• Which type of transport works against the
concentration gradient?
– Active transport
Quiz… Just for Fun
Question 4• Which type(s) of transport is bilateral?
– Passive transport
Quiz… Just for Fun
Question 5• Which type(s) of transport requires the use of
energy in the form of ATP?
– Active transport
Quiz… Just for Fun
Question 6• Which substances can cross the cell membrane
through simple diffusion? Give examples.
– Oxygen, carbon dioxide
Quiz… Just for Fun
Question 7• Which substances cannot cross the cell membrane
through passive transport?
–Substances that are too large–Substances that cannot dissolve in a lipid bilayer–Substances that are unable to move down it’s
concentration gradient
Quiz… Just for Fun
Question 8• What does it mean by moving “down its
concentration gradient”?
–Moving from an area of high concentration to an area of low concentration
= water molecule
hypotonic
hypertonic
What is the net movement of water?What will happen to the cell as a result?
Into the cellBurst - cytolysis
= water molecule
hypotonic
hypertonic
What is the net movement of water?What will happen to the cell as a result?
Out of the cellShrivel - plasmolysis
= water molecule
isotonic
What is the net movement of water?What will happen to the cell as a result?
Equal movement into and outCell is at equilibrium
= water molecule
What is the net movement of water?What will happen to the cell as a result?
= table salt molecule
Out of the cellShrivel - plasmolysis
hypertonic
hypotonic
= water molecule
What is the net movement of water?What will happen to the cell as a result?
= table salt molecule
Equal movement into and outCell is at equilibrium
isotonic
• Movements of macromolecules, such as proteins are called bulk transport.
• This occurs through either one of two processes called endocytosis or exocytosis.
Exocytosis
• Transport materials out of the cell.
• Important for expulsion of waste materials and to secrete important macromolecules, such as, enzymes and hormones.
Endocytosis
• Transport materials into the cell.
• The opposite of exocytosis.
There are 3 types of endocytosis
1. Phagocytosis (cellular eating)
2. Pinocytosis (cellular drinking)
3. Receptor-mediated endocytosis
ExocytosisExocytic vesicle immediately after fusion with plasma membrane.
Endocytosis – Phagocytosis
Used to engulf large particles such as food, bacteria, etc. into vesicles
Called “Cell Eating”
Pinocytosis
Most common form of endocytosis.
Takes in dissolved molecules as a vesicle.
Receptor-Mediated Endocytosis
Some integral proteins have receptors on their surface to recognize, bind and take in hormones, cholesterol, etc.
Receptor-Mediated Endocytosis
Animation
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/rectpr.htm
Receptor-mediated endocytosis
• Receptors on the plasma membrane will only bind to specific molecules, called ligands, for ingestion.
• Example: the uptake of cholesterol into the cell
PLEASE NOTE!
• Both endocytosis and exocytosis processes require the use of energy in the form of ATP
• Therefore, they are both forms of active transport
Quick Quiz
Question 1• What is the process by which materials are
exported out of the cell?a) Phagocytosisb) Exocytosis c) Endocytosisd) Bulk transport
Quick Quiz
Question 2 • Mammalian cells use _______ to import
cholesterol.a) Phagocytosisb) Pinocytosis c) Endocytosisd) Receptor-mediated endocytosis
Quick Quiz
Question 3• Pinocytosis is the process of “cellular drinking”
a) True b) False
Quick Quiz
Question 4• Phagosomes must fuse with lysosomes to
digest imported materials. a) True b) False
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