The Plasma Membrane Cells Chapter 7

Fluid-Mosaic Model Fluid – the plasma membrane is the consistency of olive oil at body temperature. Mosaic – membrane proteins form a collage that differs on either side of the membrane and from cell to cell (greater than 50 types of proteins)

Structure of the Plasma Membrane

Proteins of the Plasma Membrane Provide 6 Membrane Functions: 1) Transport Proteins 2) Receptor Proteins 3) Enzymatic Proteins 4) Cell Recognition Proteins 5) Attachment Proteins 6) Intercellular Junction Proteins

1) Transport Proteins Channel Proteins – channel for lipid insoluble molecules and ions to pass freely through (acts like a tunnel)~ facilitated diffusion Carrier Proteins – bind to a substance and carry it across membrane, change shape in process (acts like a pump)~ active transport

2) Receptor Proteins – Bind to chemical messengers (Ex. hormones) which sends a message into the cell causing cellular reaction

How do materials move into and out of the cell? Materials must move in and out of the cell through the plasma membrane. Some materials move between the phospholipids. Some materials move through the proteins.

Plasma Membrane Transport Molecules move across the plasma membrane by: Active Transport Passive Transport

What are three types of passive transport? Diffusion Facilitated Diffusion Osmosis ATP energy is not needed to move the molecules through.

Passive Transport 1: Diffusion Molecules can move directly through the phospholipids of the plasma membrane This is called … DIFFUSION

What is Diffusion? Diffusion is movement of molecules from a high concentration to a low concentration until equally distributed. Diffusion rate is related to temperature, pressure, state of matter, size of concentration gradient, and surface area of membrane. http://www.biologycorner.com/resources/diffusion-animated.gif

What molecules pass through the plasma membrane by diffusion? Gases (oxygen, carbon dioxide) Water molecules (rate slow due to polarity) Lipids Lipid soluble molecules (hydrocarbons, alcohols, some vitamins) Small noncharged molecules (NH3)

Why is diffusion important to cells and humans? Cell respiration Alveoli of lungs Capillaries Red Blood Cells Medications: time-release capsules

Passive Transport 2: Facilitated Diffusion Molecules can move through the plasma membrane with the aid of transport proteins This is called … FACILITATED DIFFUSION

What is Facilitated Diffusion? Facilitated diffusion is the movement of molecules from a high concentration to a low concentration with the aid of channel or carrier proteins.

What molecules move through the plasma membrane by facilitated diffusion? Ions (Na+, K+, Cl-) Sugars (Glucose) Amino Acids Small water soluble molecules Water (faster rate)

How do molecules move through the plasma membrane by facilitated diffusion? Channel and Carrier proteins are specific: Channel Proteins allow ions, small solutes, and water to pass Carrier Proteins move glucose and amino acids Facilitated diffusion is rate limited, by the number of proteins channels/carriers present in the membrane.

Why is facilitated diffusion important to cells and humans? Cells obtain food for cell respiration Neurons communicate Small intestine cells transport food to bloodstream Muscle cells contract

Passive Transport 3: Osmosis Water Molecules can move directly through the phospholipids of the plasma membrane This is called … OSMOSIS

What is Osmosis? Osmosis is the diffusion of water through a semi-permeable membrane. Free water molecules collide, bump into the membrane, and pass through.

Osmosis in action What will happen in the U-tube if water freely moves through the membrane but glucose can not pass? Water moves from side with high concentration of water to side with lower concentration of water. Movement stops when osmotic pressure equals hydrostatic pressure.

Why is osmosis important to cells and humans? Cells remove water produced by cell respiration. Large intestine cells transport water to bloodstream Kidney cells form urine

Osmosis and Tonicity Tonicity refers to the total solute concentration of the solution outside the cell. What are the three types of tonicity? Isotonic Hypotonic Hypertonic

Isotonic Solutions that have the same concentration of solutes as the suspended cell. What will happen to a cell placed in an Isotonic solution? The cell will have no net movement of water and will stay the same size. Ex. Blood plasma has high concentration of albumin molecules to make it isotonic to tissues.

Hypotonic Solutions that have a lower solute concentration than the suspended cell. What will happen to a cell placed in a Hypotonic solution? The cell will gain water and swell. If the cell bursts, then we call this lysis. (Red blood cells = hemolysis) In plant cells with rigid cell walls, this creates turgor pressure.

Hypertonic Solutions that have a higher solute concentration than a suspended cell. What will happen to a cell placed in a Hypertonic solution? The cell will lose water and shrink. (Red blood cells = crenation) In plant cells, the central vacuole will shrink and the plasma membrane will pull away from the cell wall causing the cytoplasm to shrink called plasmolysis.

Review Tonicity What will happen to a red blood cell in a hypertonic solution? What will happen to a red blood cell in an isotonic solution? What will happen to a red blood cell in a hypotonic solution?

What are three types of Active transport? 2) Exocytosis 3) Endocytosis Phagocytosis Pinocytosis Receptor-Mediated endocytosis Active Transport ATP energy is required to move the molecules through.

Active Transport Molecules move from areas of low concentration to areas of high concentration with the aid of ATP energy. Requires protein carriers called Pumps.

The Importance of Active Transport Bring in essential molecules: ions, amino acids, glucose, nucleotides Rid cell of unwanted molecules (Ex. sodium from urine in kidneys) Maintain internal conditions different from the environment Regulate the volume of cells by controlling concentration gradient

Active Transport : Exocytosis Movement of large molecules bound in vesicles out of the cell with the aid of ATP energy. Vesicle fuses with the plasma membrane to eject macromolecules. Ex. Proteins, polysaccharides, polynucleotides, whole cells, hormones, mucus, neurotransmitters, waste

Active Transport : Endocytosis Movement of large molecules into the cell by engulfing them in vesicles, using ATP energy. Three types of Endocytosis: Phagocytosis Pinocytosis Receptor-mediated endocytosis

Phagocytosis “Cellular Eating” – engulfing large molecules, whole cells, bacteria Ex. Macrophages ingesting bacteria or worn out red blood cells. Ex. Unicellular organisms engulfing food particles.

Pinocytosis “Cellular Drinking” – engulfing liquids and small molecules dissolved in liquids; unspecific what enters. Ex. Intestinal cells, Kidney cells, Plant root cells