The building blocks of life Cells Chapter 3 Cell Organelles (Plasma Membrane, Phospholipid Bilayer, Proteins) Slide 68-78 The building blocks of life

Cell membrane how it works (easy way) https://www.youtube.com/watch?v=QQgXfuFyKM4

Biology 1, Lecture 7: Cellular Membranes https://www.youtube.com/watch?v=g159zCnvpBs

Membrane Proteins and Their Functions A membrane is a collage of different proteins, often grouped together, embedded in the fluid matrix of the lipid bilayer Proteins determine most of the membrane’s specific functions

The Phospholipid Bilayer In animal cells, the cholesterol molecules that are interspersed between phospholipid molecules in the plasma membrane perform two functions: They act as a patching material that helps keep some small molecules from moving through the membrane. They keep the membrane at an optimal level of fluidity.

Plasma Membrane Proteins Some plasma membrane proteins are integral, meaning they are bound to the hydrophobic interior of the phospholipid bilayer. Others are peripheral, meaning they lie on either side of the membrane but are not bound to its hydrophobic interior.

Cell membrane proteins | Cells | MCAT | Khan Academy https://www.youtube.com/watch?v=0emD1AmfdjY

Membrane Protein Functions In animal cells, the cholesterol molecules that are interspersed between phospholipid molecules in the plasma membrane perform two functions: structural support cell identification, by serving as external recognition proteins that interact with immune system cells communication, by serving as external receptors for signaling molecules transport, by providing channels for the movement of compounds into and out of the cell

Membrane Protein Functions Six major functions of membrane proteins Transport Enzymatic activity Signal transduction Cell-cell recognition Intercellular joining Attachment to the cytoskeleton and extracellular matrix (ECM)

Types of Proteins 1) Enzymes – catalyzes covalent bond breakage or formation 2) Structural – collagen, elastin, keratin, etc. 3) Motility – actin, myosin, tubulin, etc. 4) Regulatory – bind to DNA to switch genes on or off 5) Storage – ovalbumin, casein, etc. 6) Hormonal – insulin, nerve growth factor (NGF), etc. 7) Receptors – hormone and neurotransmitter receptors 8) Transport – carries small molecules or irons 9) Special purpose proteins – green fluorescent protein, etc.

The Plasma Membrane (a) Structural support (b) Recognition (c) Communication (d) Transport Membrane proteins can provide structural support, often when attached to parts of the cell’s scaffolding or “cytoskeleton.” Binding sites on some proteins can serve to identify the cell to other cells, such as those of the immune system. Receptor proteins, protruding out from the plasma membrane, can be the point of contact for signals sent to the cell via traveling molecules, such as hormones. Proteins can serve as channels through which materials can pass in and out of the cell. Figure 5.3

(b) Enzymatic activity (c) Signal transduction Figure 7.10 Signaling molecule Enzymes Receptor ATP Figure 7.10 Some functions of membrane proteins. (a) Transport (b) Enzymatic activity (c) Signal transduction Glyco- protein (f) Attachment to the cytoskeleton and extracellular matrix (ECM) (d) Cell-cell recognition (e) Intercellular joining 12