Cell Boundaries

Macromolecules in cells! All the cell parts are made up of these macromolecules  We will start with just looking at cell boundaries

KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. cell membrane

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. forms a boundary between inside and outside of the cell cell membrane outside cell inside cell

Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. forms a boundary between inside and outside of the cell controls passage of materials cell membrane outside cell inside cell

Cell membranes are composed of two phospholipid layers. The cell membrane is made of a phospholipid bilayer. cell membrane

Cell membranes are composed of two phospholipid layers. The cell membrane is made of a phospholipid bilayer. There are other molecules embedded in the membrane. cell membrane protein cholesterol carbohydrate chain protein channel

Cell membranes are composed of two phospholipid layers. The cell membrane is made of a phospholipid bilayer. There are other molecules embedded in the membrane. The fluid mosaic model describes the membrane. cell membrane protein cholesterol carbohydrate chain protein channel

About Cell Membranes (continued) Structure of cell membrane Lipid Bilayer -2 layers of phospholipids Phosphate head is polar (hydrophilic; water loving) Fatty acid tails non-polar (hydrophobic; water fearing) Proteins embedded in membrane Phospholipid Lipid Bilayer

Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot.

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors.

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. intracellular receptor

Chemical signals are transmitted across the cell membrane. Receptors bind with ligands and change shape. There are two types of receptors. intracellular receptor membrane receptor

What organelle allows molecules to pass from outside the cell to inside the cell? of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

The Cell Membrane The Cell membrane consists of: All cells are bound by a cell membrane. The Cell membrane consists of: Lipid bilayer [Phospholipid bilayer] Proteins Carbohydrates Cholesterol

Membrane Structure

To Recap… Phospholipids are water resistant and flexible Carbohydrates are like ID tags for the cell Proteins are for stability and act like passageways for substances to enter and leave the cell.

The student is expected to: 4B investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules and 9A compare the structures and functions of different types of biomolecules, including carbohydrates, lipids, proteins, and nucleic acid

KEY CONCEPT Materials move across membranes because of concentration differences.

Diffusion and osmosis are types of passive transport. Passive transport does not require energy input from a cell. Molecules can move across the cell membrane through passive transport. There are two types of passive transport. diffusion osmosis

Diffusion and osmosis are types of passive transport. Diffusion is when molecules move down a concentration gradient. Movement is from a region of higher concentration to a region of lower concentration.

Diffusion Diffusion: The movement of a molecule, or atom from an area of high concentration to an area of low concentration until equilibrium is reached Equilibrium means equal concentrations on both sides of the membrane This naturally occurs and normally no energy is required Diffusion video

Diffusion and osmosis are types of transport. Osmosis is the diffusion of water molecules across a semipermeable membrane.

Osmosis: the movement of water across a semi permeable membrane

Some molecules can only diffuse through transport proteins. Some molecules cannot easily diffuse across the cell membrane. Facilitated diffusion is diffusion through transport proteins.

Facilitated Diffusion Movement of a molecule across a membrane when protein channels are required. Sometimes molecules are too large to pass or they are charged and can’t pass through the membrane without help When a protein channel helps a molecule this is called Facilitated diffusion Protein channels are specific for one kind of molecule

Active Transport Movement of molecules from low concentration to high concentration. (This is the opposite of diffusion)

Active Transport: Types 1) Molecular transport Used for small ions such as calcium, potassium and sodium Must pump ions across the membrane (This requires ENERGY!!) Involves changes in protein shape

Diffusion and osmosis are types of passive transport. There are three types of solutions. isotonic hypertonic hypotonic

Hypotonic Solution outside solution has a lower concentration of solute than inside the cell (Higher concentration of water outside the cell) Result: Water will move into the cell These red blood cells are in a hypotonic solution and have gained water

Hypertonic Solution outside solution has a higher concentration of solute than inside the cell (Lower concentration of water outside the cell) Results: Water moves out of the cell These Red blood cells are in a hypertonic solution and have lost water

KEY CONCEPT Cells use energy to transport materials that cannot diffuse across a membrane.

Passive transport requires no energy from the cell. Active transport is powered by chemical energy (ATP). Active transport occurs through transport protein pumps. Cells use active transport to maintain homeostasis.

Active Transport: Types 2) Endocytosis For transport of larger molecules into the cell Occurs with pockets of the cell membrane that fold into the cells creating a vacuole that is released into the cytoplasm A vacuole is a bubble-shaped part of the cell used for storage

2 types of Endocytosis a) Phagocytosis: “cell eating”- cells take up particles and form a food vacuole

Pinocytosis: “Cell drinking”- cells take up liquid from the surrounding environment.

Exocytosis Release of materials from the cell

Types of Cellular Transport Animations of Active Transport & Passive Transport high low Weeee!!! Passive Transport cell doesn’t use energy Diffusion Facilitated Diffusion Osmosis Active Transport cell does use energy Protein Pumps Endocytosis Exocytosis high low This is gonna be hard work!!