Stuff Happens

By: Paul, Sam, Tom

Model of a Cell Membrane

Taken from Human Biology by Daniel Chiras

Cell Membrane: Lipid (fat) bilayer impenetrable by water soluble materials. Distributed randomly in the membrane are proteins, glycoproteins, and cholesterol.

Proteins make gap junctions throughout the cell membrane to allow homogenous solutions to pass through the membrane to the cell.

Homogenous solutions are mixtures of two or more substances into a solution of equal density.

Integral Proteins span the lipid bilayer and they are markers while peripheral proteins are indicators of the differences between certain cells.

Selective Permeability is the practice of a cell membrane to allow only certain solutions to enter or exit through the cell membrane. It keeps nutrients in and keeps unwanted materials out.

Passive Transport is when a cell membrane allows substances to pass through it without any energy input from the cell.

There are two types of passive transport, diffusion and filtration.

There are two types of diffusion, simple and facilitated. There are also two types of filtration, solute pumping and bulk transport.

Simple Diffusion occurs when the amount of a solution is unbalanced. The molecules pass through the cell membrane in an effort to gain equilibrium. This never happens, because it is the movement of the molecules that keeps the good things coming into the cells, and the bad things leaving the cells.

Facilitated Diffusion occurs when the particles trying to enter the cell are to large to pass through the cell membrane. Instead, they pass into the cell through the proteins in the cell membrane. Facilitated diffusion uses kinetic energy in the solution to travel.

Filtration is when solutes and water need to get to the cell and they are pushed through form a high pressure gradient to a low pressure gradient.

Active Transport is when a cell membrane provides metabolic energy (ATP) that drives the transport process. Substances can’t move in the right direction to enter the cell, the cell membrane uses ATP to get the substances to where they should be. Situation in which Active Transport is needed include when cells are too large and when solutions are moving in the wrong direction.

Ribose

Adenine

Phosphates

Solute pumping is very similar to facilitated diffusion. The difference is that in solute pumping, ATP is used to move the solutions through the proteins. ATP is needed in this situation because the solutions are traveling in the wrong direction to enter the cell. The solutions pass through the proteins, and each protein allows only a certain kind of solutions to pass through it.

There are two kinds of Bulk Transport: exocytosis and endocytosis.

In Exocytosis, the cell produces hormones that form a sack around the substances. The sack hits the cell membrane and it fuses with the membrane. The sack breaks and releases the substance outside the cell.

In Endocytosis, the substances hit the cell membrane and the cell membrane encloses around the substance and it forms a sack. The sack then enters into the cell. Phagocytosis is another word for Endocytosis.

•www.people.virginia.edu/ ~rjh9u/cellmemb.html•http://www.kscience.co.uk/as/module1/endocytosis.htm•http://www.mhhe.com/biosci/genbio/enger/student/olc/art_quizzes/genbiomedia/0086.jpg

•www.sirinet.net/~jgjohnso/ actpastransp.html •http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/memb.gif •http://www.octc.kctcs.edu/gcaplan/anat/images/Image151.gif•http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/ATP.gif •www.hallym.ac.kr/~de1610/ histology/histo.html •hkn.eecs.berkeley.edu/ ~alchen/parlor/images/coh/ •www.connect.ab.ca/.../ students_tenunit2note.html