The Cell and Its

Environment

Notes

What you already know:What you already know:

All cells have an outer covering called the cell membraneAll cells have an outer covering called the cell membrane

Cells need starting materials for life-sustaining processesCells need starting materials for life-sustaining processes

Cells need to get rid of waste productsCells need to get rid of waste products

Now you will learn:Now you will learn:

How materials move into and out of the cell through the cell membrane.How materials move into and out of the cell through the cell membrane.

How energy is involved in transporting some materials into and out of cells.How energy is involved in transporting some materials into and out of cells.

How surface area affects transport in cells.How surface area affects transport in cells.

Key terms before we get started:Key terms before we get started:

Semi-Permeable (Selectively Permeable):Semi-Permeable (Selectively Permeable): Some substances can pass through Some substances can pass through but others cannot.but others cannot.

PermeablePermeable: to pass through: to pass through

Materials move across the cell’s membranes.

  A A CELL MEMBRANE CELL MEMBRANE usually permeable to usually permeable to substances such as oxygen, carbon dioxide, food, substances such as oxygen, carbon dioxide, food, and water. Substances that can move in and out and water. Substances that can move in and out of the cell do so by one of three methods: of the cell do so by one of three methods: diffusion, osmosis, or active transport.diffusion, osmosis, or active transport.

Some materials move by diffusion.

When you walk toward the shampoo section in When you walk toward the shampoo section in a store, you can probably smell a fragrance a store, you can probably smell a fragrance even before you get close. The process by even before you get close. The process by which scent spreads through the air is an which scent spreads through the air is an example of example of DIFFUSIONDIFFUSION. Diffusion is the . Diffusion is the process by which molecules spread out, or process by which molecules spread out, or move from areas where there are move from areas where there are MANYMANY of of them to areas where there are them to areas where there are FEWERFEWER of of them. them.

Diffusion occurs because the molecules in Diffusion occurs because the molecules in gasses, liquids, and even solids are in constant gasses, liquids, and even solids are in constant MOTIONMOTION in all directions. This random in all directions. This random movement of molecules tends to spread movement of molecules tends to spread molecules out until they are molecules out until they are EVENLYEVENLY distributed. But diffusion does more than just distributed. But diffusion does more than just spread a scent around a room. Cells use spread a scent around a room. Cells use diffusion to carry out important life diffusion to carry out important life FUNCTIONSFUNCTIONS. For example, the oxygen needed . For example, the oxygen needed for respiration enters cells by diffusion. for respiration enters cells by diffusion. Similarly, the carbon dioxide produced by Similarly, the carbon dioxide produced by respiration leaves cells by diffusion. respiration leaves cells by diffusion.

Concentration

Diffusion occurs naturally as particles move from Diffusion occurs naturally as particles move from an area of an area of HIGHERHIGHER concentration to an area of concentration to an area of LOWERLOWER concentration. The concentration of a concentration. The concentration of a substance is the substance is the NUMBERNUMBER of particles of that of particles of that substance in a specific substance in a specific VOLUME.VOLUME. For example, For example, if you dissolved 9 grams of sugar in 1 liter of if you dissolved 9 grams of sugar in 1 liter of water, the concentration of the sugar solution water, the concentration of the sugar solution would be 9 g/L. When there is a difference in the would be 9 g/L. When there is a difference in the concentration of a substance between two concentration of a substance between two areas, areas, DIFFUSIONDIFFUSION occurs. occurs.

Concentration

Generally, the greater the Generally, the greater the DIFFERENCEDIFFERENCE in in concentration between two areas, the more concentration between two areas, the more rapidly diffusion occurs. As the difference in rapidly diffusion occurs. As the difference in concentration decreases, diffusion slows concentration decreases, diffusion slows down. The number of particles moving to one down. The number of particles moving to one area is area is BALANCEDBALANCED by the number moving in by the number moving in the other direction. Particles are still moving the other direction. Particles are still moving in all directions, but those movements in all directions, but those movements DO DO NOT CHANGENOT CHANGE the concentrations. the concentrations.

Check Your Notes

Summarize what happens during diffusion. Summarize what happens during diffusion. (Remember a summary only includes the most (Remember a summary only includes the most important information.)important information.)

During diffusion, molecules, which are in During diffusion, molecules, which are in constant motion in all directions, spread out in constant motion in all directions, spread out in an equal mixture.an equal mixture.

Diffusion in Cells

Diffusion is one way by which materials move Diffusion is one way by which materials move ININ and and OUTOUT of cells. Small molecules such as of cells. Small molecules such as oxygen can pass through tiny gaps in the oxygen can pass through tiny gaps in the CELL CELL MEMBRANEMEMBRANE by diffusion. Diffusion is a form of by diffusion. Diffusion is a form of PASSIVEPASSIVE transport. In passive transport, transport. In passive transport, materials move without using the cell’s materials move without using the cell’s ENERGYENERGY. . Cells benefit from passive transport because Cells benefit from passive transport because some materials can move through various cell some materials can move through various cell membranes without any input of energy. membranes without any input of energy.

Check Your Notes

What is passive transport?What is passive transport? (Your answer (Your answer should mention energy!) should mention energy!)

Passive transport allows materials to move Passive transport allows materials to move without using the cell’s energy.without using the cell’s energy.

Osmosis

You have learned about the importance of You have learned about the importance of WATERWATER. Water molecules move through cell . Water molecules move through cell membranes by diffusion. The diffusion of membranes by diffusion. The diffusion of water through a membrane is given a special water through a membrane is given a special name, name, OSMOSISOSMOSIS. If the concentration of . If the concentration of water is higher outside a cell than inside, water is higher outside a cell than inside, water moves water moves INTOINTO the cell. If the the cell. If the concentration of water is lower outside a cell, concentration of water is lower outside a cell, water moves water moves OUT OF OUT OF the cell. the cell.

Osmosis

You can easily observe the effect of osmosis You can easily observe the effect of osmosis on on PLANTSPLANTS. If you forget to water a plant, it . If you forget to water a plant, it wilts. Why? The soil dries out, and the plants wilts. Why? The soil dries out, and the plants roots have no roots have no WATERWATER to absorb. As a result, to absorb. As a result, water leaves the plant cells by water leaves the plant cells by OSMOSISOSMOSIS and and they shrink. If you water the plant, water they shrink. If you water the plant, water becomes available to enter the shrunken cells becomes available to enter the shrunken cells by osmosis. The leaves will return to normal by osmosis. The leaves will return to normal as water moves into the cells. as water moves into the cells.

Without water, a plant droops. The Without water, a plant droops. The cells have little water in their cells have little water in their vacuoles. vacuoles.

Water moves into leaf cells by Water moves into leaf cells by osmosis and fills the vacuoles.osmosis and fills the vacuoles.

Review Your Notes

How are the processes of diffusion and How are the processes of diffusion and osmosis alikeosmosis alike??

Osmosis is a special term for water diffusion.Osmosis is a special term for water diffusion.

Some transport requires energy.

Not all materials that move in and out of a cell Not all materials that move in and out of a cell can do so by diffusion. For cells to carry out can do so by diffusion. For cells to carry out life functions, materials must move from areas life functions, materials must move from areas of of HIGH HIGH concentration into areas of concentration into areas of LOW LOW concentration. This process of moving concentration. This process of moving materials against a concentration requires materials against a concentration requires ENERGYENERGY..

Active Transport

ACTIVE ACTIVE Transport is the process of using Transport is the process of using energy to move materials through a energy to move materials through a membrane. This process is different from membrane. This process is different from diffusion and other types of passive transport, diffusion and other types of passive transport, which which DO NOTDO NOT require energy. require energy.

Check your notes

How is active transport different from passive How is active transport different from passive transport?transport?

Active requires energy, passive does not.Active requires energy, passive does not.

Active Transport

Cells use active transport to perform Cells use active transport to perform important life functions, including the removal important life functions, including the removal of excess of excess SALT SALT from the body. Consider the from the body. Consider the example of active transport in marine iguanas. example of active transport in marine iguanas. These lizards swim and feed in the salty These lizards swim and feed in the salty OCEANOCEAN. As a result, they soak up a lot of salt. . As a result, they soak up a lot of salt. Too much salt would seriously damage the Too much salt would seriously damage the iguana’s cells, so the cells must get rid of the iguana’s cells, so the cells must get rid of the excess.excess.

Marine Iguana

Active Transport

The solution to the marine iguana’s salt The solution to the marine iguana’s salt problem is found in two small problem is found in two small GLANDS GLANDS above above its eyes. Cells in these glands remove its eyes. Cells in these glands remove EXCESS EXCESS salt from the blood by active salt from the blood by active transport. Even when cells in these glands transport. Even when cells in these glands have a higher concentration of salt than that have a higher concentration of salt than that of the blood, the cells use chemical of the blood, the cells use chemical ENERGY ENERGY to continue taking salt out of the blood. The to continue taking salt out of the blood. The gland forms a droplet of salt, which the iguana gland forms a droplet of salt, which the iguana easily blows through its easily blows through its NOSRILSNOSRILS. .

Active Transport

You may not be able to blow salt out of your You may not be able to blow salt out of your nostrils, but your nostrils, but your KIDNEYSKIDNEYS help to keep help to keep healthy salt levels in your body. Kidneys filter healthy salt levels in your body. Kidneys filter wastes from your blood by wastes from your blood by ACTIVEACTIVE transport. transport. Cells in the kidneys remove excess salt from Cells in the kidneys remove excess salt from the blood.the blood.

Check Your Notes

If a marine iguana were to spend a few days in If a marine iguana were to spend a few days in a freshwater tank, would it continue to blow a freshwater tank, would it continue to blow salt droplets from its nostrils? Why or why salt droplets from its nostrils? Why or why not?not?

After it expels the salt that was already inside of After it expels the salt that was already inside of it, it will not release anymore because it is not it, it will not release anymore because it is not absorbing any.absorbing any.

Endocytosis

Cells also need to move materials that are too Cells also need to move materials that are too LARGE LARGE to go through the cell membrane or a to go through the cell membrane or a protein channel. As the diagram below protein channel. As the diagram below illustrates, illustrates, ENDOCYTOSIS ENDOCYTOSIS occurs when a occurs when a large bit of material is captured within a pocket large bit of material is captured within a pocket of the membrane. This pocket breaks off and of the membrane. This pocket breaks off and forms a forms a PACKAGE PACKAGE that moves into the cell. that moves into the cell. Cells in your body can use endocytosis to fight Cells in your body can use endocytosis to fight bacteria and viruses by bacteria and viruses by ABSORBINGABSORBING them. them.

Exocytosis

When a cell needs to get rid of large When a cell needs to get rid of large materials, the process of endocytosis is materials, the process of endocytosis is REVERSEDREVERSED. In exocytosis, a membrane . In exocytosis, a membrane within the cell encloses the material that within the cell encloses the material that needs to be removed. This package moves to needs to be removed. This package moves to the cell membrane, joins with it, and the the cell membrane, joins with it, and the material is expelled. Cells often use material is expelled. Cells often use exocytosis to flush out waste materials or to exocytosis to flush out waste materials or to expel proteins or hormones made by the cell.expel proteins or hormones made by the cell.

Check Your Notes

Compare and contrast endocytosis and Compare and contrast endocytosis and exocytosis.exocytosis.

Active Transport BrainPop

BrainPop