Cell Membrane Test

What is a cell?

the structural unit of all living things

Name the three basic points of cell theory.

1. A cell is the basic structural and functional unit of living organisms.
2. All organisms are made of cells.
3. All existing cells are produced by other living cells.

In a cell, properties and features of life are _______________.

evident

What is the difference between prokaryotic and eukaryotic cells?

prokaryotic cells don't have membrane-bound organelles and eukaryotic cells do

Where is the DNA of both a prokaryotic cell and a eukaryotic cell found? Why is it different?

in the cytoplasm of a prokaryotic cell and in the nucleus of an eukaryotic cell; the nucleus is a membrane-bound organelle and prokaryotic cells don't have those

What are the main parts of eukaryotic cells?

cell membrane, cytoplasm, nucleus, intracellular fluid

What is the cytoplasm of a eukaryotic cell?

where organelles are suspended

What is the intracellular fluid of a eukaryotic cell?

water, also called cytosol

What is another name for the cell membrane?

plasma membrane

What is the model of the plasma membrane called?

fluid mosaic model

The plasma membrane is a sea of ___________________ in which ___________________ float like icebergs.

lipids; proteins

What are the two main components of the cell membrane?

half lipids and half proteins

What three lipids are a part of the cell membrane?

phospholipids, glycolipids, and cholesterol

What percentage of the lipids in the cell membrane are phospholipids?

75

The phospholipids in the cell membrane arrange themselves in a ____________________ ___________________ when they are part of it.

phospholipid bilayer

What percentage of the lipids in the cell membrane are glycolipids?

5

Glycolipids are part ______________ and part ________________.

lipid and sugar

Glycolipids are only found sticking out of the cell, or on the side with _________________________ fluid.

extracellular

What percentage of the lipids in the cell membrane are cholesterol (a steroid)?

20

In the cell membrane, cholesterol is found where, and why?

tucked in with nonpolar tails; because it is nonpolar and therefore hydrophobic

What is the lipid bilayer of the cell membrane?

two back-to-back layers of three types of lipid molecules

_________________ and _____________________ scattered among a double row of ______________________.

glycolipids and cholesterol; phospholipids

What is an integral protein?

a protein packed tightly with the membrane; parts with heads and parts with tails of phospholipids; embedded in the membrane

What is a peripheral protein?

loosely associated with the membrane; only with the heads of phospholipids

What is an integral transmembrane protein?

integral and on both sides of the membrane

What is glycocalyx?

sugar coating on outside of cell; made from sugars of glycoproteins and glycolipids

What is glycocalyx used for?

cell identification

Glycocalyx is __________________ in every organism's cells.

different

What are the functions of membrane proteins?

formation of channel, transportation, reception, cell identification, linking, act as enzymes

What is the top of a cell called?

apical surface

What is the bottom of a cell called?

basal surface

What are the three membrane junctions?

microvilli, cilia, flagellum

What is the purpose of microvilli?

absorption

What is the purpose of cilia?

movement of material over the apical surface of the cell

What is the purpose of a flagellum?

movement of the cell

What do microvilli do?

absorb nutrients

What stand microvilli up?

actin proteins

What do microvilli look like?

fingers

What are microvilli covered by?

plasma membrane

We have ___________________ to absorb more nutrients from _____________________; they also ___________________ surface area of the ______________________________________.

microvilli; intestines; increase; plasma membrane

What make up cilia?

proteins called microtubules covered in plasma membrane

Cilia are _________________ than microvilli.

longer

What make up a flagellum?

microtubules covered in plasma membrane

How does a flagellum work?

when microtubules bend, whip-like flagellum propels the cell forward

Where are special membrane junctions found?

in animals

What hold cells together in tissues?

glycocalyx and special membrane junctions

What are the three special membrane junctions?

tight junctions, gap junctions, desmosomes

What is a tight junction?

storage junction inside of the bladder that holds cells together in a tissue

What is one place where a tight junction is used?

to keep urine inside the bladder instead of leaking into the body cavity

How do tight junctions work?

protruding membrane proteins meet with each other and seal intercellular space or space between cells (seal two cells together)

What is a gap junction?

a communication junction that allows ions to flow from cell to cell and allows for synchronized contraction of muscles

How do gap junctions work?

membrane proteins from both cells form passageways from one cell to another; made from proteins called connexxon proteins

What is a desmosome?

a junction that helps dissipate the pressure by spreading it across the cells; keep cells from splitting with button-like adhesion

Where are desmosomes typically found?

in places with a lot of mechanical pressure

How do desmosomes work?

protein plaques in each cell send out cadherin proteins to bond cells, intermediate filaments attach

What are the two types of transport across the plasma membrane? What is the difference?

passive transport does not use energy and active transport uses energy to transport material (ATP)

What are the two types/categories of passive transport?

diffusion and filtration

Does diffusion happen in all cells?

yes

True or False: all types of cells have a plasma membrane.

true

Does filtration happen in all cells?

only in certain cells

What is diffusion?

the random mixing of particles that occurs in a solution as a result of the kinetic energy of the particles

True or False: diffusion can happen with or without a cell membrane.

true

What happens in diffusion?

molecules move away from areas of higher concentration to areas where the concentration is lower; particles bump into each other which separates the higher concentration so that it spreads

In diffusion, molecules diffuse _______________ or ______________ their concentration gradient (high concentration to low concentration).

along or down

True or False: energy is not needed for diffusion.

true

What is a concentration gradient?

difference in concentration between two areas (between ICF and ECF)

The greater the difference in concentration between two areas the faster the ________________________________ of the particles, or the faster diffusion will happen.

net diffusion

What influences the speed of diffusion?

molecule size and temperature

Smaller molecules diffuse _________________ than large molecules.

faster

Diffusion eventually reaches _____________________ (evenly spread).

equilibrium

Cells don't _______________________ want to reach equilibrium.

always

Due to its _____________________ core, the _____________ ___________________ is a physical __________________ to free diffusion.

hydrophobic; plasma membrane; barrier

Anything with a _________________ or _________________ ___________________ ______________ don't permeate easily.

charge; polar covalent bonds

What are the types of diffusion?

simple diffusion, facilitated diffusion (via a carrier or channel), osmosis

All types of diffusion are ____________________ transport.

passive

What is simple diffusion?

unassisted diffusion of lipid-soluble, nonpolar or very small particles

What can pass through the membrane with simple diffusion?

oxygen, carbon dioxide, fat soluble vitamins, and steroid hormones

What type of protein is a channel?

integral transmembrane protein

What is an aqueous pore?

water-filled pore

How does a channel work?

transports a substance through an aqueous pore from one side of the membrane to the other

Substances are always moving ______________ their concentration gradient (high to low) through a channel.

down

Channels are __________________; each channel is specific for a particular __________.

selective; ion

What are the two types of channels?

leakage channels and gated channels

Which type of channels are always open?

leakage channels

Gated channels are . . .

closed most of the time, triggered to open for a very brief amount of time

How do chemically gated channels open?

from a chemical

How do mechanically gated channels open?

from mechanical pressure

How do voltage gated channels open?

when the charge changes

How can channels be inhibited?

by removing/adding channels

What is facilitated diffusion via a carrier?

a transmembrane integral protein that moves substances that are too large to pass through a channel

Facilitated diffusion via a carrier functions like a _____________________ __________.

revolving door

Carriers are ____________________ and can show ______________________.

selective; saturation

The rate of facilitated diffusion is ____________________ because permeability of membrane can be altered by changing the number of _______________________ ___________________________.

controllable; individual carriers/channels

What is osmosis?

diffusion of a solvent (water) through a selectively permeable membrane

Why can water cross the membrane?

it is small

What are aquaporins?

water specific channels of transmembrane proteins

When does osmosis occur?

whenever the water concentration differs on the two sides of the membrane

What is osmolarity?

the total concentration of all solute particles in a solution

Water moves ______________ water's concentration gradient (less concentration to high concentration), towards more solutes.

down

True or False: both passive and active transport happen in all types of cells.

true