8-1 Cell Membrane

8-1 Cell Membrane

Cell Membrane

•  Every cell is surrounded by a ______

Functions

•  provides ______and ______ the cell

•  recognizes foreign material

•  gatekeeper – ______

•  communicates with other cells

Homeostasis

•  ______.

•  Achieved by controlling the movement of substances across the cell membrane

•  Lipid Bilayer

Phospholipid

•  is a specialized lipid made of ______“head” and ______ “tails.”

•  Main component of the cell membrane

•  Cells are suspended in a fluid environment.

–  phosphate head = ______= ______.

–  fatty acid tails = ______= ______.

•  Lipid Bilayer

Lipid Bilayer

•  the phospholipids form a ______ as a result of water inside and outside the cell

•  The nonpolar tails, repelled by water, make up the ______ of the lipid bilayer.

•  The polar heads are attracted to the water, so they point ______ of the lipid bilayer.

–  One layer of polar heads faces the ______, while the other layer is in contact with the cell’s ______.

Lipid Bilayer

•  Only certain substances can pass through the lipid bilayer.

–  only ______ substances can pass.

•  ______are repelled by the ______ interior of the lipid bilayer.

•  Membrane Proteins

Where are proteins found within the membrane

•  face ______ the cell

•  face ______ the cell

•  stretch across the lipid bilayer and face ______.

•  Proteins are made of ______. Some amino acids are polar, and others are nonpolar.

•  The ______ of polar and nonpolar parts of the protein to water help hold the protein in the membrane.

Membrane Proteins

Types of proteins

•  Cell-surface markers

–  ______

–  unique chain of sugars acts as a marker to identify each type of cell.

•  Receptor proteins

–  enable a cell to ______

–  binds to certain substances outside the cell resulting in ______.

•  Membrane Proteins

Types of proteins

•  Enzymes

–  ______ in the cell membrane

–  helps with important biochemical reactions inside the cell.

–  ______

•  aid the movement of substances that the cell needs but cannot pass through of the lipid bilayer.

Membrane Proteins

Summary

•  One way that a cell maintains homeostasis is by controlling the movement of substances across the cell membrane.

•  The lipid bilayer is selectively permeable to small, nonpolar substances.

•  Proteins in the cell membrane include cell-surface markers, receptor proteins, enzymes, and transport proteins.