BIOL 1201 : Chapter 7

The ____________ is the boundary that separates the living cell from its surroundings

plasma membrane

The plasma membrane is __________ permeable.

selectively

What are transport proteins often responsible for?

controlling passage across cellular membranes

review pictures

review pictures

What is the membrane in the fluid mosaic model?

a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids

What are membranes held together by?

mainly weak hydrophobic interactions

Most of the _____ and some _____ can move sideways within the membrane

lipids ; proteins

What are the membrane proteins?

integral proteins and peripheral proteins

What are Peripheral proteins?

are bound to the surface of the membrane

What are Integral proteins?

penetrate the hydrophobic core

Integral proteins that span the membrane are called ______________.

transmembrane proteins

How does cell recognize each other?

by binding to molecules, often containing carbohydrates, on the extracellular surface of the plasma membrane

Membrane carbohydrates may be covalently bonded to what?

lipids (forming glycolipids) or, more commonly, to proteins (forming glycoproteins)

If a plasma membrane were compared to a sandwich, ____________ would be considered the filling.

Hydrophobic tails

Membrane structure results in what?

selective permeability

A _________ must exchange materials with its surroundings, a process controlled by the ____________.

cell ; plasma membrane

Plasma membranes are _______ permeable, regulating the cells molecular traffic.

selectively

________ (nonpolar) molecules, such as ___________, can dissolve in the lipid bilayer and pass through the membrane rapidly.

Hydrophobic ;hydrocarbons

_________ molecules including ions and polar molecules do not cross the membrane easily.

Hydrophilic

Review pictures

Review pictures

What re Transport proteins ?

allow passage of hydrophilic substances across the membrane

What does carrier proteins do?

bind to molecules and change shape to shuttle them across the membrane

Which of the following molecules is most likely to passively diffuse across the plasma membrane?

carbon dioxide

What is passive transport?

diffusion of a substance across a membrane with no energy investment

What is diffusion?

the tendency for molecules to spread out evenly into the available space

Diffusion of a population of molecules may be ________.

directional

Where does substances diffuse down?

concentration gradient (high to low)

The _________ of a substance across a biological membrane is ______ because no energy is expended by the cell to make it happen.

diffusion ; passive transport

What is Osmosis?

the diffusion of water across a selectively permeable membrane

Water diffuses across a membrane from the region of _______ to the region of _______ until the solute concentration is equal on both sides

lower solute concentration ; higher solute concentration

What is hypotonic?

Lower concentration outside compared to inside

What is isotonic?

Equal concentration inside and outside

What is hypertonic?

Higher concentration outside compared to inside

Image of hypotonic?

Image of isotonic?

Image of hypertonic?

The internal solute concentration of a plant cell is about 0.8M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?

1.0 M

The "cell" in the beaker in the figure below is made up of a semipermeable membrane that allows water to pass but not salt. The solution in the "cell" is

________ compared to the solution in the beaker.

hypertonic

In which direction will there be net movement of water?

to the left

What is Facilitated Diffusion?

- Passive Transport Aided by Proteins

- Ion channels facilitate the transport of ions

- Some ion channels, called gated channels, open or close in response to a stimulus

What are gated channels?

they open or close in response to a stimulus

______ facilitate the transport of ions.

Ion channels

What uses energy to move solutes against their gradients?

Active transport

______ diffusion is still passive because the solute moves down its concentration gradient, and the transport requires no energy.

Facilitated

Where does active transport requires energy from?

ATP hydrolysis, to move substances against their concentration gradient

In passive transport, what does the concentration go from?

high to low

In active transport, what does the concentration go from?

low to high

The cytoplasm of a certain cell, such as a neuron, already has a high concentration of K+ ions. How can K+ ions continue to enter the cell?

active transport

Bulk transport across the plasma membrane occurs by what?

exocytosis and endocytosis

Small molecules and water enter or leave the cell through the ________ or via _______.

lipid bilayer ; transport proteins

Large molecules, such as ______ and ______, cross the membrane in bulk via vesicles.

polysaccharides ; proteins

Bulk transport requires ______.

energy

What is Phagocytosis?

Cell eating

What is Pinocytosis?

bring in small solutes by bulk (cell drinking)

What is Receptor-Mediated Endocytosis?

cells will have receptors in membrane and bind specifically with them to form a vesicle