Cell Transport

TEKS (4) Science concepts. The student knows that cells are the basic structures of all living things with specialized parts that perform specific functions and that viruses are different from cells. The student is expected to: investigateexplaincellular processes homeostasistransport of molecules (B) investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules

Important Vocabulary 1.PhosphoLipid bi-layer 2.Membrane 3.Integral proteins 4.Selectively permeable 5.Diffusion 6.Facilitated diffusion 7.Osmosis 8.Active transport 9.Aquaporins 10.Solute, solvent, solution 11.Concentration gradient 12.Slope 13.Hypertonic 14.Hypotonic 15.Isotonic 16.Equilibrium 17.Net-movement 18.Osmotic potential 19.Osmotic pressure 20.Turgor 21.Plasmolysis 22.Cytolysis

Plasma (Cell) Membrane (Phospholipid Bilayer) Outer boundary of cytoplasm Semipermiable (only certain molecules enter & leave) Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

Phospholipid bilayer A double layer that is an effective barrier for most molecules Hydrophobic = “water fearing” tails in the center, prevent most things from entering Hydrophilic = “water loving” heads attract water to edges of membrane Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

Fluid Mosaic Model Cell membranes are mosaics that contain many different molecules like proteins, cholesterol, glycoproteins, etc.

Proteins embedded in membranes can be: Channels “gates” to interior for transporting into & out of cytoplasm Receptors “windows” for gathering information about cell surroundings Markers “name tags” that identify type of cell to others

Membranes are Selectively permeable The plasma membrane enables only certain molecules to enter or exit the cell. Why is this important?

Surface to volume ratio Why are larger organisms are multicellular? Why aren’t they just one big ol’ cell? Because materials must be transported across cell membranes, maximizing the amount of membrane surface area increases transport efficiency.

Comparing surface area to volume (Complete the calculations with your table partner and be ready to share) Surface area: 6 mm x 6 mm x 6 sides = ___ mm 2 Volume: ___ mm 3 S / V = ___ Surface area: 3 mm x 3 mm x 6 sides x 8 cubes = ___ mm 2 Volume = ___ mm 3 S / V = ___

Types of passive transport Diffusion random spread of molecules from higher to lower concentration Examples?

Types of transport across membranes 1.Diffusion (Simple Diffusion) movement from an area of high concentration to an area of low concentration. 2.Facilitated diffusion large molecules (ie. Glucose or water) move through protein channels in the cell membrane. 3.Active transport movement of molecules against the concentration gradient – requires cellular energy

current (Concentration gradient) Passive or Active transport?

Passive vs Active transport: which requires energy output?

Diffusion across a membrane In which pictures do we see the greatest gradient? In which pictures do we see equilibrium?

Osmosis across a membrane

Osmosis Diffusion of water across a selectively permeable membrane from higher water purity to lower water purity When solutions of varying water concentrations are found across a membrane, the solutions are given names. Hypertonic Hypotonic Isotonic

Types of osmotic solutions Hypotonic High water purity & less solutes = water moves in & cell expands and may burst (Cytolysis) Isotonic Equal solutes & water, so equal movement of water into and out of the cell Hypertonic Low water purity because of more solutes = water moves out & cell shrinks (Plasmolysis)

Cells in hypotonic solutionCells in hypertonic solution Cells in isotonic solution

Cells in various solutions Copy this chart in your IAN LYSE TURGID NORMAL FLACCID PLASMOLYSIS Plant, fungus, algae, bacteria animal Hypotonic Isotonic Hypertonic

Achieving equilibrium

Active transport video

Types of Active Transport Endocytosis cell brings molecules in. Pinocytosis Liquids are brought in.

Phagocytosis Phage means to “eat” large particles (food or bacteria) are surrounded & engulfed by cell. Examples = an ameba feeding & a white blood cell destroying an invader. Why are white blood cells called MacroPhages?

“Cell eating”

Exocytosis cell deposits particles outside of cytoplasm Secretion = cell products given off Excretion = wastes products given off

The Big Idea: Cell structure is related to it’s function All cells are different. Cell specialization → different cells have different jobs. Each cell serves different needs. Diversity on a individual scale helps stabilize the organism Diversity on a large scale helps stabilize the ecosystem