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2 Plasma Membrane
June 3 Class 17
25
Biology
Undergraduate 2
06/03/2015

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Term
Describe the differences between phagocytosis, pinocytosis, and Receptor-mediated endocytosis
Definition
Phagocytosis-grabs out to get food particle(pseudopodium) and brings in as food vacuole
Pinocytosis-plasma membrane creates a vesicle and grabs things nearby
Receptor-mediated Endocytosis- Calls a receptor to catch the ligand and brings it in a coated vesicle
Term
What are lysosomes and are they acidic or basic?
Definition
 Membrane-bound pocket
containing hydrolytic
enzymes
 Acidic
Term
What are the functions of lysosomes?
Definition
Process harvest from phagocytosis
Carry our autophagy(self digestion)
Term
How do lysosomes carry out autophagy?
Definition
Digestion of old organelles
 Recycle macromolecules
Term
How do lysosomes process harvest from phagocytosis?
Definition
Engulf organisms of food
into vacuole
 Lysosome fuses with
vacuole
 Contents are digested
Term
What are 4 characteristics of the cell membrane?
Definition
Segregate domains
◦ Serve as barrier to passage of some materials while
allowing passage of others
◦ Allow information to cross (signals)
◦ Provide a surface for organization
Term
What is the membrane structure?
Definition
◦ Phospholipid bilayer
◦ Also:
 Cholesterol
 Proteins
 Carbohydrates
Term
What is the Fluid Mosaic model?
Definition
◦ Fluid Mosaic Model
 Membrane is mosaic of
phospholipid and
embedded proteins
 Random distribution
 Free mobility
 Not entirely true –
subdomains: Lipid Rafts
Term
Describe membrane fluidity?
Definition
-Membranes are
dynamic – components
constantly moving
- Lateral movement
- Non-directed flipping from one side of bilayer rarely happens, not physiologically relevant
Term
What is membrane fluidity affected by?
Definition
 Temperature
 Unsaturated vs.
saturated hydrocarbons
 Cholesterol
 Integral proteins
Term
What are the two types of membrane proteins?
Definition
Integral and peropheral
Term
When a membrane protein is integral what does it mean?
Definition
- Directly within membrane
 Cross membrane (transmembrane)
 Embedded in one side
Term
When a membrane protein is peripheral what does it mean?
Definition
-Loosely attached
 Associate with phospholipids
 Associate with integral proteins
Term
What are the wide range of functions that membrane protein do?
Definition
Transport
 Enzymatic activity
 Signal transduction
 Cell recognition
 Intercellular joining
 Cytoskeletal attachment
Term
What targets for viruses?
Definition
Membrane proteins
Term
How do membrane proteins target viruses?
Definition
 Viruses infect cells by specific binding to cell-surface
proteins
 Targets for immunological, pharmacological or genetic
intervention
Term
What are the products of the endomembrane system?
Definition
transmembrane proteins
Term
Describe how the transmembrane proteins are made?
Definition
Soluble proteins will be secreted, trans-membrane proteins will
remain in plasma membrane or within the endomembrane
system
Term
Describe membrane permeability
Definition
◦ Selectively permeable, based on size, hydrophobicity
 Easily cross: small, uncharged non-polar
 Do not easily cross: large, hydrophilic (charged/polar)
Term
What is diffusion and how does it happen?
Definition
◦ Random movement of molecules toward equilibrium
-molecules spread out in space
◦ From High concentration to Low
- ‘Down’ concentration gradient
Term
What is osmosis and how does it occur?
Definition
◦ Diffusion of water across selectively permeable membrane
 High water concentration to low
 Low solute concentration to high
Term
What is tonicity?
Definition
Ability of surrounding solution to cause a cell
to gain or lose water (through osmosis)
Term
What are the terms for hypotonic, isotonic, and hypertonic cells in animals and plants?
Definition
Animal Hypo-Lysed Iso-Normal Hyper-Shriveled
Plant Hypo-Turgid(normal) Iso-Flaccid Hyper-Plasmolyzed
Term
What are the three types of transport in the plasma membrane, describe the types of energy required as well.
Definition
Passive transport
◦ Diffusion across
membrane
 No energy required
Facilitated Diffusion
◦ Passive transport via
proteins
 No energy required
Active Transport
◦ Against concentration
gradient
 Energy required (ATP)
Term
What tends to happen to cells that are Hypotonic, Isotonic, and Hypertonic?
Definition
Hypotonic solution will cause cell to gain water
 fewer solutes in solution than in cell
Isotonic will cause no change
 same level of solutes as in cell
Hypertonic solution will cause cell to lose water
 more solutes than in cell
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