The Cell and its Environment

The Cell and its Environment Chapter 3 Section 2 p.80-85

Cell Membrane • It selects what comes in and goes out. • It is also permeable. • per·me·able • \pər-mē-ə-bəl\ • having pores or openings that permit liquids or gases to pass through • Cell membranes are selectively permeable.

Cell Membrane • The cell membrane is selectively permeable which allows the movement of substances, especially oxygen, water, food molecules, carbon dioxide, and waste products, into or out of the cell. Here fat molecules are allowed to pass through, but large molecules are NOT.

There are different ways that substances can move into and out of a cell. • Materials move into and out of cells through either passive transport or active transport. • Transport means to move.

Passive Transport • Passive – inactive, not active, not participating • Transport – to move • Passive transport - transport of a substance across a cell membrane where no energy is used The boy doesn’t need energy to go down this hill. (Band-Aids perhaps )

Passive Transport • Movement of molecules from a more crowded to a less crowded area WITHOUT the use of energy. • Movement occurs when there are unequal concentrations of a substance inside and outside of the cell. • The molecules will move from the • left (where it is crowded) to the right (less crowded) • Right click on the picture and choose to open hyperlink. • If not, then go to: • http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion.gif

Types of Passive Transport • There are two types of passive transport. • Diffusion • dif·fu·sion • (d-fyzhn) • movement of molecules from a region of higher concentration to a region of lower concentration. • Doesn’t require energy To begin with, the particles are all near one corner of the glass. If the particles all randomly move around ("diffuse") in the water, then the particles will eventually become distributed.

Diffusion • 1 Why do we smell bread baking throughout the house? The answer is diffusion. A good way to describe diffusion is the moving of molecules from a place where they are concentrated close together to a place where they are less concentrated or farther apart. When molecules are spread out evenly, diffusion seems to stop.2 Smells travel in the air by diffusion. Because molecules are always moving, some molecules leave the bread as it is baking. They are vented with the excess heat from the oven. These tiny molecules of bread travel through the air throughout the house to our noses.3 Have you ever passed by a bakery and noticed the delicious smells down the street from it? If the wind is blowing, there will be more mixing of the molecules in the air. That can either make the smell reach you sooner, or it can spread the molecules out so that you don't notice the smell as much. Since our brains are used to the smell of air, we don't smell the oxygen, nitrogen, or carbon dioxide. Instead, we smell the other molecules mixed with our air. This is why we smell the bread baking, smoke, perfume, or other smells.

Types of Passive Transport • There are two types of passive transport. • Osmosis • os·mo·sis • oz-moh-sis • Osmosis is a type of diffusion where molecules move from crowded to a low crowd (high concentration to low concentration). • diffusion of water through a membrane • Doesn’t require energy Water is moving from high (crowded) to low (not crowded) concentration

Wishful Thinking…

Cell Transport • So far we have looked at times when the cell is moving particles in and out without using energy…. Passive transport • Well, there are times when the cell needs to move a molecule and energy is required known as active transport.

Active Transport • Active transport • movement of molecules from a less crowded to a more crowded area WITH the use of energy. • Molecules are "carried" into or out of the cell using some of the cell's energy. Uses ENERGY

Types of Active Transport Active transport describes what happens when a cell uses energy to transport something. We're talking about the movement of individual molecules across the cell membrane. The liquids inside and outside of cells have different substances. Sometimes a cell has to work and use some energy to maintain a proper balance of ions and molecules. Two types: 1.Transport proteins 2. Engulfing Using energy due to moving from a low up to a high concentration

Type of Active Transport – Transporting Proteins

Type of Active Transport - Engulfing Not just sacks of fluid. A macrophage--a type of white blood cell--engulfs its bacterial prey in this colorized electron microscope image.

Hmmmmmmm… • Why do cells need to be able to move molecules/particles in and out of a cell anyway???

HOMEOSTASIS • To maintain stable internal conditions • Even cells want to be balanced and stable

Weeee!!! high low This is gonna be hard work!! high low Summary: Types of Cellular Transport • Passive Transport cell doesn’t use energy • Diffusion • Osmosis • Active Transport cell does use energy • Transport Proteins • Engulfing

The Cell and its Environment