Bio 101 Chapter 7: Membrane Structure and Functions

ATP, ADP, AMP

ATP (3 phosphate) when used is broken down into ADP+P (2 phosphate), and so forth with AMP

Active Transport

against a concentration gradient requires energy (ATP) requires carrier proteins called solute pumps includes sodium ion/potassium ion pump

osmoregulation

controlling water balance

hypotonic

has a lower concentration of solutes outside the cell than inside the cell. In an attempt to balance the concentrations of solutes inside and outside the cell, water will rush into the cell, and can cause it to burst.

Endocytosis

"bringing in the cell" phagocytosis: cellular eating pinocytosis: cellular drinking receptor-mediated endocytosis: specific for specific molecules

Exocytosis

"kicking out of the cell" also called vesicular transport

Bulk Transport

Active Transport. Requires energy. Endocytosis and Exocytosis

Active and passive transport of solutes across a membrane typically differ in which of the following ways?

Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy.

isotonic

An isotonic solution is one in which the concentration of solutes is the same both inside and outside of the cell

Diffusion

Diffusion is the movement of particles down their concentration gradient.

Membrane Proteins

Functions: transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment

Fluid Mosaic Model

Membranes are fluid, membrane proteins and phospholipids can drift about in the membrane. The diverse proteins found in and attached to membranes perform many important functions. The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic (unsaturated and saturated fatty acid) tails clustered in the center.

You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

The similarity of the drug molecule to other molecules that are transported into the target cells. If the target cells have transport proteins that specifically bind to certain molecules, they may bind with and transport a drug that is similar in structure.

The permeability of a biological membrane to a specific polar solute may depend on which of the following?

The types of transport proteins in the membrane. The lipid bilayer will be impermeable or very poorly permeable to polar or charged solutes. The presence of the correct transport protein will determine the permeability.

In this diagram of the plasma membranes of two adjoining cells, identify the protein indicated by the white arrow, including its function

a receptor protein that binds with a signaling molecule and relays the message into the cell by activating other molecules inside the cell. Signaling proteins are part of signal transduction pathways that transmit external chemical signals into the cell.

Passive Transport

down a concentration gradient, no input of energy. simple diffusion (hydrophobic) osmosis facilitated diffusion: (hydrophilic)

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

Plasma Membrane Components

lipids (phospholipids and cholesterol) proteins carbohydrates

A white blood cell engulfing a bacterium is an example of _____.

phagocytosis

Plasma Membrane Structure

phospholipid bilayer: hydrophobic center, hydrophilic exterior. cholesterol makes membrane less deformable. proteins: integral vs. peripheral carbohydrates: short, branched chains of sugars. cell-cell recognition. glycolipids vs. glycoproteins

Plasma Membrane Functions

protection isolation (separates inside from outside environment) regulated transport (selectively permeable) communication cell recognition

permeability

related to structure: permeable to hydrophobic substances. use of proteins for transport of many hydrophilic substances (sugars, ions, amino acids)

Osmosis

simple diffusion of water across a semi-permeable membrane. dependent on the number of solute particles present

What kinds of molecules pass through a cell membrane most easily?

small and hydrophobic

Structure A is a _____.

solute

The force driving simple diffusion is _____, while the energy source for active transport is _____.

the concentration gradient; ATP

hypertonic

the concentration of solutes is greater outside the cell than inside it. causes the cell to become dehydrated and shriveled

Structure B is a _____.

transport protein

Simple Diffusion

unaided passage of substance across the membrane. Dependent on: diameter of molecules, concentration gradient, electrical charge, temperature

Facilitated Diffusion

use of integral proteins to transport hydrophilic substances 1. carrier-mediated (aminos) 2. channel-mediated (ions usually, water) and protein helper