Bio 160 Chapter 4

is the simplest structural unit of a living

organism

cell

What are the 3 components of cell theory?

1. 1. Cells are the fundamental units of life

2. 2. All living organisms are composed of cells

3. 3. All cells come from preexisting cells.

Which statement is one of the tenets of cell theory?

a. All cells take in energy and matter from the

environment.

b. Cells are separated from their environment by a cell

membrane.

c. All cells come from preexisting cells.

d. All cells contain mitochondria.

e. Cells sustain the living state through chemical

transformations.

c

A general function of all cellular membranes is to

a. regulate which materials can enter or leave the cell.

b. support the cell and determine its shape.

c. produce energy for the cell.

d. produce proteins for the cell.

e. move the cell.

a

The cytosol and _______ are two components of the

cytoplasm in a prokaryotic cell.

a. Golgi apparatus

b. chloroplasts

c. mitochondria

d. ribosomes

e. smooth ER

D

What is the fluid mosaic model of cell membranes?

Lipids and proteins move laterally though the membrane.

Phospholipids form

bilayers

Phospholipids form bilayers with the charged,

hydrophilic “heads” of the phospholipid bilayer are on the ___ of the membrane

outside

The nonpolar hydrophobic fatty acid “tails” of the phospholipid bilayer are on the ___of the membrane

inside.

The hydrophobic interior prevents

molecules and ions through the membrane.

A general function of all cellular membranes is to

a. regulate which materials can enter or leave the cell.

b. support the cell and determine its shape.

c. produce energy for the cell.

d. produce proteins for the cell.

e. move the cell.

A section of the cell membrane is shown below. Which

letter(s) in the figure represent transmembrane proteins?

a. a and b

b. b and c

c. c and e

d. b, only

e. d and e

Membrane fluidity is influenced by:

• Lipid composition—short, unsaturated chains

increase fluidity; cholesterol alters interactions

among fatty acid side chains

• Temperature—fluidity decreases in cold

conditions; some organisms alter lipid

composition in cold environments

Membranes differ in lipid composition by

phospholipids vary in terms of fatty acid chain

length, degree of saturation, and polar groups.

at least partly

embedded in phospholipid bilayer. Hydrophobic

regions interact with membrane interior;

hydrophilic regions interact with the aqueous

environment.

integral membrane proteins

covalently

attached to fatty acids or other lipid groups

Anchored membrane proteins

no hydrophobic

groups; not embedded in the bilayer—polar or

charged regions interact with exposed parts of

integral membrane proteins or with charged

heads of phospholipids.

Peripheral membrane proteins

extend through the

bilayer; they may have domains with different

functions on the inner and outer sides of the

membrane

Transmembrane proteins

carbohydrate attached to a lipid

Glycolipid

oligosaccharide attached to a

protein

Glycoprotein

many carbohydrates attached

to a protein

Proteoglycan

Which compounds in a biological membrane form a barrier

to the movement of hydrophilic materials across the

membrane?

a. Integral membrane proteins

b. Carbohydrates

c. Lipids

d. Amino acids

e. Peripheral membrane proteins

biological membranes

allow some substances, but not others, to pass

Selective permeability

does not require energy;

substances diffuse down a concentration

gradient

Passive transport

requires energy and the

assistance of specialized membrane proteins.

Active transport

random movement of particles toward a state of equilibrium; a net movement from regions of higher concentration to regions of lower concentration

Diffusion

Diffusion in water is slow; speed depends on:

• Diameter of molecules

• Temperature

• Concentration gradient

• Area and distance

Simple diffusion

net movement of water from a region

of lower solute concentration to a region of

higher solute concentration

osmosis

pressure that must be applied to a solution to prevent flow of water

across a membrane by osmosis:

= CRT

osmotic pressure

solute particles per liter of water

(solute concentration)

Osmotic pressure can be quantified by

osmolarity

relative concentration of solutes on either

side of a membrane; determines direction and extent of net water movement

tonicity

solutions have equal solute

concentrations are…

isotonic

solution has a lower solute concentration is…

hypotonic

solution has a higher solute

concentration is…

hypertonic

Which statement regarding the red blood cells in the figure

is true?

a. Osmosis occurs when a cell goes from condition B to C

but not from condition B to A.

b. The concentration of solutes inside cell C is higher than

in the solution surrounding the cell.

c. Diffusion of solutes out of the cell is causing the events

shown in the transition from condition B to A.

A molecule is present at two different concentrations on

either side of a membrane. The molecule will have the

greatest diffusion rate if the concentration is _______ mM

on one side and _______ mM on the other.

a. 20; 30

b. 50; 60

c. 30; 30

d. 15; 50

is the internal pressure against the cell wall—as it builds up, it prevents more water from entering

Turgor pressure

passive transport of solutes down their concentration gradient with the help of integral transmembrane proteins

Facilitated diffusion

form channels across the

membrane

channel proteins

bind to a solute to speed up diffusion

Carrier proteins

channel proteins that allow specific ions to pass through; water can “hitchhike” along with some ions

Ion channels

Ligand-gated—the stimulus is

a ligand, a chemical signal

Voltage-gated—the stimulus is

a change in electrical charge difference across the membrane

glucose is quickly broken down in the cell, so there is always a strong concentration gradient that favors glucose

uptake

glucose transporters

A cell shrinks if the solution surrounding it is _____________ to its contents and will expand if the solution surrounding it is _____________ to its contents.

hypertonic; hypotonic

In facilitated diffusion, the diffusion rate of a specific

molecule across a membrane does not continue to

increase as the molecule’s concentration difference across

the membrane increases beyond a certain point. Why?

a. Facilitated diffusion requires the use of ATP.

b. As the concentration difference increases, molecules

interfere with one another.

c. The diffusion constant depends on the concentration

difference.

d. The carrier proteins become saturated.

In reference to membranes, the characteristic of allowing certain substances to pass through while other substances are excluded.

selective permeability

Diffusion across a membrane; may or may not require an integral membrane protein.

passive transport

he energy-dependent transport of a substance across a biological membrane against a concentration gradient—that is, from a region of low concentration (of that substance) to one of high concentration

active transport

the process of random movement of particles toward a state of equilibrium.

diffusion

the change in solute concentration with distance in a given direction. The greater the concentration gradient, the more rapidly a substance diffuses.

concentration gradient

A transport protein in plant and animal cell membranes through which water passes by osmosis

(channels for movement of water)

aquaporins

Movement of water across a selectively permeable membrane, from a hypotonic solution to a hypertonic solution.

osmosis

The property of aqueous solutions that determines the direction of osmotic water movement when water can move from one solution to another. When water moves by osmosis between two solutions, it always moves from the lower to the higher osmotic pressure. Each individual dissolved entity (regardless of chemical nature) contributes approximately equally to the osmotic pressure of a solution.

osmotic pressure

uses chemical-bond energy released during the hydrolysis of ATP or another chemical reaction, or light energy, to transport a solute against its concentration gradient.

primary active transport

An integral membrane protein (anti-porter) that carries out primary active transport of ions; it uses energy from ATP to pump sodium ions out of a cell and potassium ions into the cell.

sodium-potassium (Na+ -K+) pump

A form of active transport that does not use as an energy source; rather, transport is coupled to ion diffusion down a concentration gradient established by primary active transport. Also called coupled transport or co-transport.

secondary active transport

Within the cytoplasm, a membrane-enclosed compartment that is associated with other organelles; the Golgi apparatus is one example

It is used to transport large molecules or particles out of the cells

vesicles

Transport of large molecules or particles out of the cells

exocytosis

A process by which liquids or solid particles are taken up by a cell through invagination of the cell membrane

endocytosis

a specialized cell engulfs a large

particle or another cell, forming a food vesicle

(phagosome). This usually fuses with a

lysosome, where the contents are digested.

phagocytosis

vesicles are smaller and bring in

fluids and dissolved substances.

pinocytosis

brings specific large molecules into a cell via specific receptors.

receptor-mediated enocytosis

The ___ of a cell determines its metabolic

activity and thus the cell’s need for resources and

rate of waste production per unit of time.

volume

The ___ of a cell determines rate at which

substances can enter or leave the cell.

surface area

a meshwork of protein

filaments:

• Supports and maintains cell shape

• Maintains position of organelles and other particles within the cell.

• Moves organelles and other particles within the cell

• Interacts with extracellular structures to anchor cell in place.

cytoskeleton

actin polymers: actin monomers attach to the “plus end” and detach at the “minus end” of the filament.

these help maintain cell shape and cause

localized shape changes in a cell:

• Cytoplasmic streaming

• Division of an animal cell into two daughter cells following mitosis.

• Formation of pseudopodia that enable some cells, such as Amoeba, to move

microfilaments

the filaments can shorten (more detachment) or lengthen (more assembly), allowing for quick assembly or breakdown of the cytoskeleton.

dynamic instability

In muscle cells, interaction of___ and the motor protein myosin, are responsible for cell contractions.

actin filaments

At least 50 different kinds in six molecular

classes

• Tough, ropelike protein assemblages; more permanent than other filaments; no dynamic instability

• Anchor cell structures in place

• Resist tension, maintain rigidity

intermediate filaments

are long, hollow, unbranched cylinders about 25 nm in diameter. Microtubules are polymers of the protein tubulin.

microtubules

A protein that polymerizes to form microtubules

tubulin

A long, whiplike appendage that propels cells. Prokaryotic flagella differ sharply from those found in eukaryotes

Some cells have projections from their cell membrane termed

flagella

A hairlike organelle used for locomotion or signaling. Generally shorter than a flagellum.

cilia

Plants, archaea, bacteria, fungi, and some protists build cell walls of

cellulose, chitin, or proteins

provide structural support, and protection from physical damage and pathogens.

Cell walls

A material of heterogeneous composition surrounding cells and performing many functions, including adhesion of cells.

Animal cells have an _____ of collagen and gel-like proteoglycans. It has many

functions:

• Hold cells together in tissues.

• Contribute to physical properties of cartilage, skin, bone

• Help filter materials passing between different tissues, e.g., in the kidney

• Help orient cell movements during embryonic development and tissue repair.

extracellular matrix

a fibrous protein found extensively in bone and connective tissue

collagen

The extracellular matrix of animal cells

a. is composed of cellulose.

b. contains lysosomes.

c. limits the cell volume by remaining rigid.

d. helps orient cell movements during embryonic

development

Proteins such as integrins connect the ____

They span the cell membrane; reversible binding sites connect to microfilaments or intermediate filaments on the interior of the cell, and to collagen in the extracellular matrix.

Cell membrane to the extracellular matrix.

A community of microorganisms embedded in a polysaccharide matrix, forming a highly resistant coating on almost any moist surface

biofilm

Specialized structures associated with the cell membrane that join cells in multicellular organisms. Some contribute to cell adhesion, others to intercellular communication

cell junctions

prevent substances from moving through spaces between cells. For example, the epithelium of the urinary bladder contains tight junctions to prevent urine from leaking into the adjacent abdomen

tight junctions

hold adjacent cells together with stable protein connections. This provides mechanical stability for tissues such as skin that are under stress due to movement. Desmosomes do, however, permit some materials to move around in the extracellular matrix between cells.

desmosomes

are channels that run between membrane pores in adjacent cells and allow substances such as ions, small molecules, and electric signals to pass between cells. In the heart, for example, gap junctions allow the rapid spread of electric current mediated by ions so the heart muscle cells can beat in unison.

Gap junctions

A cytoplasmic strand connecting two adjacent plant cells.

are similar to gap junctions between animal cells, but they allow passage of larger substances.

allow water, ions, small molecules, hormones, and even some RNA and protein molecules to move between connected cells

plasmodesmata

What is a function of the cell junction shown in the figure?

a. Exchange of a lot of material between adjacent cells

b. Conducting electrical activity, as in the heart

c. Preventing substances in a lumen from leaking into the

spaces between the epithelial cells lining the lumen

Lack a nucleus and membrane-enclosed internal compartments.

Protein structures separate certain substances from others in the cell.

Tiny encapsulin nanocompartments enclose a single protein, such as peroxidase, that breaks down toxic substances.

Some cell functions occur in cell regions, likely separated by the cytoskeleton.

prokaryotes