Proteins and The Cell
Membrane
Unit 5: Homeostasis and Cell Transport
• Transporters
• Channel Protein
• Carrier Protein
• Enzymes
• Cell Surface Receptors = Receptor Protein
• Cell Surface Identity Markers = Cell Recognition
Protein
• Attachments to Cytoskeleton = Junction Protein
Do you know the functions of these proteins
associated with the cell membrane?
Channel Protein
Involved in the
passage of molecules
through the
membrane
Facilitated Diffusion
uses channel proteins
Carrier Protein
 Combine with a
substance to help
move it across the
membrane.
 Ion Pumps are
carrier proteins.
Transporters
Enzyme Proteins are embedded in the membrane and
catalyze specific reactions.
• ATP synthase is an enzyme embedded in the inner
mitochondrial membrane as well as the thylakoid
membrane of the chloroplast.
• Adenylate cyclase is an enzyme involved in ATP
metabolism. Cholera bacteria release a toxin that
interferes with the functioning of this enzyme resulting
in Na+ and water leaving intestinal cells. Individuals may
die from severe diarrhea.
Enzymes
• Receptor Proteins have specific shapes that can only
bind to specific molecules.
• Receptor Proteins receive signals when the molecules
bind with them.
Pygmies are short, not because they do not produce
enough growth hormone, but because their plasma
membrane growth hormone receptors are faulty and
cannot interact with growth hormone.
Receptor Proteins
• Glycoproteins enable cells of multicellular organisms
to recognize each other.
The HMC (major histocompatibility complex)
glycoproteins are different for each person, so organ
transplants are difficult to achieve. Cells with foreign HMC
glycoproteins are attacked by white blood cells responsible
for immunity.
Identity Markers = Cell
Recognition Proteins
Cells within multicellular organisms are part of tissues.
Junction proteins join cells so that a tissue can fulfill a
function.
• Junction proteins help attach cells to neighboring cells
and to the cytoskeleton of each cell.
• The nervous system of animal embryos rely upon the
junction proteins during development. The junction
proteins help pinch off to form neural tube!
Attachments to Cytoskeleton =
Junction Proteins
• Which proteins embedded within the cell membrane
catalyze specific chemical reactions?
• Which proteins are responsible for cells receiving signals
from other cells?
• Which proteins are involved with the major
histocompatibility complex?
• Which proteins join cells together to form tissues?
• Which proteins act as ion pumps?
• Which proteins enable substances to diffuse through the
cell membrane?
Summing it all up!