Animal Cell

Plant Cell

Journey through the cell f24 f24

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 PHOSPHOLIPID BILAYER

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 Transport 2)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. QU9g QU9g 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) Moves from HIGH water potential (low solute) to LOW water potential (high solute)

Diffusion of H 2 O Across A Membrane High H 2 O potential Low solute concentration Low H 2 O potential High solute concentration

Aquaporins Water Channels Protein pores used during OSMOSIS WATER MOLECULES

Cell in Isotonic Solution CELL 10% NaCL 90% H 2 O 10% NaCL 90% H 2 O What is the direction of water movement? The cell is at _______________. equilibrium ENVIRONMENT NO NET MOVEMENT

Cell in Hypotonic Solution CELL 10% NaCL 90% H 2 O 20% NaCL 80% H 2 O What is the direction of water movement?

Cell in Hypertonic Solution CELL 15% NaCL 85% H 2 O 5% NaCL 95% H 2 O What is the direction of water movement? ENVIRONMENT

Video qc-I qc-I

Cells in Solutions

Isotonic Solution NO NET MOVEMENT OF H 2 O (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?

hypotonichypertonic isotonic hypertonicisotonic 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 1eS4 1eS4

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 cell Burst - cytolysis

= water molecule hypotonic hypertonic What is the net movement of water? What will happen to the cell as a result? Out of the cell Shrivel - plasmolysis

= water molecule isotonic What is the net movement of water? What will happen to the cell as a result? Equal movement into and out Cell 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 cell Shrivel - 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 out Cell 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

Exocytosis Exocytic 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 Most common form of endocytosis. Takes in dissolved molecules as a vesicle 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 4fv/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)Phagocytosis b)Exocytosis c)Endocytosis d)Bulk transport

Quick Quiz Question 2 Mammalian cells use _______ to import cholesterol. a)Phagocytosis b)Pinocytosis c)Endocytosis d)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