Membrane Structure and Function

67 %
33 %
Information about Membrane Structure and Function

Published on October 14, 2008

Author: wdorsey


BIOLOGY: : BIOLOGY: Membrane Structure and Function History of the Membrane Idea : History of the Membrane Idea 1925— Gorter & Grendel—hydrophobic tails inward. 1940s— Daniel and Davson—sandwich model: (protein, phospholipid, and protein.) 1972— Singer and Nicholson—fluid mosaic model. Membrane Models : Membrane Models Fluid-Mosaic Model Membrane is a fluid phospholipid bilayer in which protein molecules are either partially or wholly embedded. Functions of the Plasma Membrane : Functions of the Plasma Membrane Regulates the passage of materials into and out of the cell. Receives chemical messages from other cells, e.g. hormones, growth factors, neurotransmitters. Maintains structural and chemical relationships with other cells. Protects the cell, helps in cell movement, secretion, and in transmitting impulses. Plasma Membrane as a Fluid : Plasma Membrane as a Fluid At body temperature, consistency of olive oil. Each phospholipid molecule can move sideways at ~ 2 mm/s Most proteins are free to drift along it. Cholesterol stiffens and strengthens the membrane, helping to regulate fluidity. Slide 6: Plasma membrane is differentially permeable. Passive Transport - No ATP requirement. Diffusion - Movement of molecules from a high to low concentration until equilibrium is reached. Osmosis - Diffusion of water across a selectively permeable membrane due to concentration differences. Osmotic pressure, the greater the pressure, the more water will diffuse in that direction. Active Transport - Requires carrier protein and ATP. Figure 8.12 The water balance of living cells : Figure 8.12 The water balance of living cells Membrane-Assisted Transport : Membrane-Assisted Transport Large marcomolecules are transported into or out of the cell by vesicle formation. Endocytosis - Cells take in substances with vesicles Phagocytosis – solid material. Pinocytosis - Liquid particles. Exocytosis - Vesicles secrete substances out of cell Plasma Membrane Structure : Plasma Membrane Structure Plasma membrane is a phospholipid bilayer. Hydrophilic polar heads face outside, and hydrophobic nonpolar tails face each other. Proteins may be peripheral or integral. Peripheral proteins are found on the inner membrane surface. Integral proteins are embedded in the membrane. Carbohydrate Chains : Carbohydrate Chains In animal cells, the carbohydrate chains give the cell a “sugar coat,” called the glycocalyx which helps protect the cell adhesion between cells in the reception of signal molecules cell-to-cell recognition. give a “fingerprint” (tissue rejection) give rise to A, B, and O blood groups Protein Functions : Protein Functions Channel Proteins - pass molecules through Carrier Proteins - bond with substance to help it through Cell Recognition Proteins - Help body recognize foreign substances and itself. Receptor Proteins - Protein changes shape to bring about cellular change. Enzymatic Proteins - Carry out metabolic reactions directly. Transport by Carrier Proteins : Transport by Carrier Proteins Carrier proteins combine with molecules which are then transported through the membrane. Facilitated Transport (facilitated diffusion) molecules move with the gradient by combining with carrier proteins. Active Transport molecules move against the gradient by combining with carrier proteins. (requires ATP) Figure 8.15 The sodium-potassium pump: a specific case of active transport : Figure 8.15 The sodium-potassium pump: a specific case of active transport Cell Surface Modifications : Cell Surface Modifications Cell Surfaces in Animals—junctions between cells Adhesion Junctions Intercellular filaments between cells. bladder & stomach Tight Junctions Impermeable barriers. intestines and kidneys. Gap Junctions Membrane channels join Allows small ions & molecules to pass between cells. Cell Surface Modifications : Cell Surface Modifications Extracellular Matrix Meshwork of polysaccharides and proteins Can be flexible or hard, as in bone.

Add a comment

Related presentations

Related pages

Cell Membrane Structure and Function - The Biology Corner

Chapter 5 - Membrane Structure and Function The Plasma Membrane. fluid mosaic model, semi-permeable (selectively permeable), double layer of phospholipids ...
Read more

Membranes | Celebrate Cytochemistry | Gwen V. Childs, Ph.D.

Membranes; Membrane Specializations; Membrane Architecture; Membrane Studies; Cilia, flagella, and centrioles; ... Mitochondrial Structure-Function ...
Read more

Cell Membrane: Functions, Role & Structure - Video ...

Cell Membrane Functions. The plasma membrane of a cell has two main roles: It is a physical barrier. It regulates exchange of materials with its surroundings.
Read more

Plasma membrane Structure and Function ~ Biology Exams 4 U

Cell membrane is the ‘line of control’ of the factory of life "the cell". This living structure is responsible for keeping individuality and also acts ...
Read more

Chapter 7: Membrane Structure and Function

AP Biology Reading Guide Julia Keller 12d Fred and Theresa Holtzclaw Chapter 7: Membrane Structure and Function
Read more

Membrane Structure and Function - Phoenix College | Offers ...

Membrane Structure and Function All cells have a plasma or cell membrane , which contains the cell. Scanning electron micrograph (SEM) of adipocytes (Ad)
Read more

Cell membrane - Wikipedia, the free encyclopedia

The cell membrane (or plasma membrane or plasmalemma) surrounds the cytoplasm of living cells, physically separating the intracellular components from the ...
Read more

The Plasma Membrane - YouTube

Educational video about the plasma membrane. ... Structure and Function of the Cell Membrane - Duration: 15:01. Craig Savage 76,292 views. 15:01
Read more

Membrane Structure and Function

Membrane Structure and Function 5 Read This! Some molecules, such as glucose, use gated channels as shown in Model 3; however, not all channels are
Read more

Chapter 4 Membrane Structure and Function

4.1 Plasma Membrane Structure and Function The plasma membrane is a phospholipid bilayer in which protein molecules are either partially or wholly embedded
Read more