A&P Lecture 5 - Cells: The Living Units

Part B

Active transport

uses ATP to move solutes across a membrane

Active transport requires

proteins

Symport system

two substances are moved across a membrane in the same direction

antiport system

two substances are moved across the membrane in opposite directions

Primary active transport

Hydrolysis of ATP phosphorylates causing conformational changes in

Secondary active transport is

Use of an exchange pump, indirectly to drive the transport of other solutes

Vesicular transport

Transport of large particles and macromolecules
across plasma membranes

Exocytosis

moves substance from the cell interior
to the extracellular space

Endocytosis

enables large particles and
macromolecules to enter the cell

Transcytosis

moving substances into, across, and
then out of a cell

Vesicular trafficking

moving substances from one
area in the cell to another

Phagocytosis

pseudopods engulf solids and bring
them into the cell’s interior

Fluid-phase endocytosis

the plasma membrane
infolds, bringing extracellular fluid and solutes into
the interior of the cell

Receptor-mediated endocytosis

clathrin-coated
pits provide the main route for endocytosis

Non-clathrin-coated vesicles

caveolae that are
platforms for a variety of signaling molecules

Membrane potential

Voltage across a membrane

Resting membrane potential

the point where K+
potential is balanced by the membrane potential

Steady state

potential maintained by active
transport of ions

Steady state

potential maintained by active
transport of ions

Cell Adhesion Molecules (CAMS)

Anchor cells to the extracellular matrix

CAMS assist in movement of

cells past one another

CAMS rally protective

white blood cells to injured or infected areas

Contact signaling

important in normal development and immunity

Electrical signaling

voltage-regulated “ion gates” in nerve and muscle tissue

Chemical signaling

neurotransmitters bind to
chemically gated channel-linked receptors

Operation of a G Protein

An extracellular ligand (first messenger), binds to a
specific plasma membrane protein

G-protein: an enzyme that produces a

second messenger inside the cell

G-protein: Second messenger activates

kinase

The activated kinase can trigger

a variety of cellular responses

Cytoplasm

material between plasma membrane
and the nucleus

Cytosol

largely water with dissolved protein, salts,
sugars, and other solutes

Cytoplasmic organelles

metabolic machinery of
the cell

Inclusions

chemical substances such as
glycosomes, glycogen granules, and pigment

Cytoplasmic Organelles

Specialized cellular compartments

Mitochondria

Double membrane structure with shelflike cristae

The mitochondria provides most of the cell’s ATP`

via aerobic cellular respiration

Mitochondria contain

their own DNA and RNA

Ribosomes are

granules containing protein and rRNA

Ribosomes are the

site of protein synthesis

Free ribosomes synthesize

soluble proteins

Membrane bound ribosomes synthesize proteins

to be incorporated into membranes

Endoplasmic Reticulum

Interconnected tubes and parallel membranes
enclosing cisternae

ER is continuous with

nuclear membrane

Two varieties of endoplasmic reticulum

Rough ER and smooth ER

Rough ER

External surface studded with ribosomes

Rough ER is responsible for the

synthesis of integral membrane proteins

mRNA

ribosome complex is directed to rough ER
by a signal-recognition particle (SRP)

Smooth ER

Tubules arranged in a looping network

Smooth ER catalyzes the following reactions in various

organs of the body