Biology: 3-3: Cell Membrane: Part B NOTES

flexible

1st characteristic of Fluid Mosaic Model: the cell membrane is ____, not rigid. The phospholipids in each layer can move from side to side & slide past each other, so the membrane acts like a FLUID.

mosaic

2nd characteristic of Fluid Mosaic Model: the variety of molecules on the membrane is like an arrangement of colorful TILES with different textures & patterns that make up a dynamic ____.

receptor

A ____ detects a signal molecule & carries out an action in response.

ligand

A ____ is a molecule that acts as a signal when it binds to a receptor.

can cross

A ligand that ____ the cell membrane can bind to an intracellular receptor.

cannot cross; binding to

A ligand that ____ the cell membrane can send a message to a cell by ____ a membrane receptor, which then changes shape.

oxygen, carbon dioxide, steroids

Because the cell membrane is mostly lipid, it only allows lipid-soluble substances like ____ (3) to pass through.

between, nonpolar

Cholesterol is located ____ the fatty acid chains. Would it be polar or nonpolar?

size, polarity, concentration

How a particular molecule crosses the membrane depends on the molecule's ____, ____, & ____ inside versus outside the cell.

1. nonpolar 2. polar 3. large

In general, 1. small ____ molecules easily pass through the cell membrane. 2. small ____ molecules are transported via proteins. 3. ____ molecules are moved in vesicles.

CELL MEMBRANE

Name #1 (UPPERCASE)

PROTEINS

Name #2 (UPPERCASE)

CYTOPLASM

Name #3 (UPPERCASE)

CARBOHYDRATE CHAIN

Name #4 (UPPERCASE)

LIPID

Name #5 (UPPERCASE)

EXTRACELLULAR SPACE

Name #6 (UPPERCASE)

1. charged phosphate (polar) attracted to water 2. glycerol 3. 2 fatty acids chains tails (non-polar) avoid water

Name the 3 major parts of a phospholipid molecule.

permeability

Selective ____ means that the cell membrane allows some, but not all, molecules to cross.

homeostasis

Selective permeability enables a cell to maintain ____ in spite of unpredictable, changing conditions outside the cell.

F

T/F: membrane is fluid, because the phospholipids in each layer can move from side to side, in and out of the cell, by sliding past each other, and by spinning in circles.

molecules

The FLUID MOSAIC MODEL describes the arrangement of the ____ that make up a cell membrane. The model includes BOTH the fluidity of the membrane and the variety of molecules that make up the membrane.

proteins

The cell membrane also consists of ____ (lowercase) that can be: 1. Markers 2. Receptors 3. Transporters 4. Enzymes

double

The cell membrane consists of a ____ layer of phospholipids along with a variety of other molecules.

phospholipid bilayer

The cell membrane consists of a ____: 1. It acts as a barrier (selectively permeable) 2. It has fluid (components can move around)

proteins, carbohydrates, cholesterol

The cell membrane is made of 2 phospholipid layers embedded with other molecules, such as ____ (3).

boundary, passage, shape

The cell membrane: 1. Forms a ____ between the cell & the outside environment. 2. Controls the ____ of materials into & out of a cell. 3. Helps it keep its ____.

nonpolar (not charged)

The fatty acids "tail" is ____.

polar (charged)

The phosphate group and glycerol form a "head" that is ____.

False

True/False: A selectively permeable membrane allows all molecules to cross.

glucose, amino acids, ions, water

Water soluble substances like ____ (4) need the help of the various proteins in order to move across the membrane.

hydrophobic, nonpolar

What 2 words describe the INTERIOR of the cell membrane?

phospholipid

What type of lipid would #2 be?

channel

What type of protein would #4 be?

The properties of polar heads & nonpolar tails cause the phospholipids to arrange themselves in layers, like a sandwich

Why do the phospholipids surrounding the cell form a bilayer?

carbohydrates

____ help identify cell types

intracellular

____ receptors are located inside the cell. They are bound by molecules that CAN cross the membrane.

membrane

____ receptors bind to molecules that CANNOT enter the cell. When bound, the receptor transmits the signal inside the cell by changing shape.

phospholipids

____ strengthen the cell membrane.

cholesterol

____ strengthens the cell membrane

Proteins

____(Uppercase) help materials cross the membrane & are also part of the cytoskeleton.

enzyme

assists chemical reactions inside the cell

transport protein

helps substances move across the cell membrane

cell-surface marker

identifies cell types

receptor protein

recognizes & binds to substances outside the cell (detects a signal molecule & performs an action in response)