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