Unit 2.5 Investigating Cell Transport

“All living things are composed of-”

One or more cells

Are plant and animal cells the same?

No but similar

Define cytoplasm

Fluid substance in a cell that supports the organelles

Define organelle

Small units that perform specialized functions within a cell

Define cell membrane

Controls the movement of materials in and out of the cell and allows the exchange of food and gases

Define nucleus

Control centre of the cell

Where is the nucleolus? What does it make?

Nucleus; makes ribosome parts

Define ribosomes

Makes proteins

Define endoplasmic reticulum

Passageway for materials moving in the cell; connects nuclear membrane to cell membrane

Define Golgi bodies

Packages and secretes proteins from the cell

Define mitochondria

Powerhouse of the cell

Define vacuoles

Storage areas for food, minerals, water

Define lysosomes

Contain digestive enzymes that break down food molecules

Define microfilaments

Pipe-like structures; provide shape and support for cell movement

Define microtubules

Protein-rich rods; for organelle movement

Define centrioles

Paired structures involved in cell division

Define flagella

Help the cell move/swim around

Define cilia

Fine hairs on the cell’s surface

What are 2 uses of the cell membrane?

1. Separates cytoplasm from the external environment

2. Controls what chemicals/waste get in/out

What is the main purpose of the cells’ membrane?

So the inside of the cell can be kept chemically different from its external environment

What composes the cell membrane?

Phospholipids

What 2 things make up a phospholipid?

A head and a tail

What 2 things are important about a phospholipid head?

1. Hydrophilic

2. Phosphate group

What 2 things are important about a phospholipid tail?

1. Hydrophobic

2. (Glycerol head) attached to two fatty acid chains

Why is having a phospholipid membrane so great for cell membranes?

Water-seeking head and fat-seeking tail means two of these molecules will join tail-to-tail when in water

What 2 molecules are inserted into cell membranes?

Proteins and cholesterol

What causes there to be proteins and cholesterol in the cell membrane?

Bends in the tail of the unsaturated fatty acid chain

What is cholesterol’s purpose in the cell membrane?

Maintains fluid condition by fixing breaks

What is cholesterol’s effect in the phospholipid bilayer at low and high temperatures?

At low temperatures keeps the phospholipids apart; at high temperatures attracts the phospholipids to stabilizes the membrane

What are proteins’ purpose in the cell membrane?

Function as channels where ions/molecules can travel in and out of the cell

What 3 things make up the fluid-mosaic model of the cell membrane?

Lipid bilayer, proteins, and cholesterol

What 2 things does “fluid” mean in the fluid mosaic model?

1. Cell membrane isn’t solid allowing material to pass through

2. Membrane can constantly adjust itself to maintain seal around cytoplasm

What does “mosaic” mean in the fluid-mosaic model?

Membrane contains several kinds of molecules embedded in it

Where are glycoproteins in the cell membrane? What are their two purposes?

Embedded in the membrane; act as receptor sites for hormones; aid in the cell’s adhesion to other cells

Define selective permeability in the cell membrane

Membrane regulates what enters and exits

What is membrane transport?

Controlled gateway for molecules moving in and out of the cell

What are the 3 ways of membrane transport?

1. Passive transport

2. Active transport

3. Vesicles for larger molecules

What is passive transport?

Movement of materials across a cell membrane without using cell energy

What are the 3 types of passive transport?

1. Diffusion

2. Osmosis

3. Facilitated diffusion

What is diffusion?

Movement of molecules from area of high concentration to low. “Moving along the concentration gradient”

What 2 molecules have no trouble getting through the cell membrane? Why?

Oxygen and CO₂; because of diffusion- they’re small and uncharged

What is an every-day example of diffusion?

Adding red dye to water- will slowly spread until equal everywhere

When concentrations become the same, what is this called?

Equilibrium

What 3 factors affect the speed of diffusion?

1. State (gases are faster than liquids)

2. Temperature (faster at higher temperatures)

3. Size of the molecule (large molecule cannot diffuse across the membrane)

What is osmosis?

Diffusion of water across a selectively permeable membrane; water molecules move from region of high water to low water (low solute to high solute) until equilibrium is reached

What are the 3 categories of osmosis?

1. Isotonic

2. Hypertonic

3. Hypotonic

What is isotonic osmosis?

Concentration of solutes surrounding the cell is equal to cell cytoplasm; solutes are at equilibrium, no net movement of water occurs

What is hypertonic osmosis?

Fluid surrounding the cell has a higher solute concentration than the cytoplasm so water diffuses out of the cell

What is hypotonic osmosis?

Solute concentration of the fluid surrounding the cell is less than the cytoplasm so water diffuses into the cell

What is an osmometer?

Tube with a permeable membrane on one end. Known solute concentration is placed inside the tube. Placed in another solution, change in height of the solution in the tube indicates osmotic potential. If water leaves the tube them the tube is hypotonic. If water enters the tube then the tube is hypertonic

What is facilitated diffusion?

When molecules are too big, need “helper” molecules to get into cells. Called transport proteins. Move materials in/out of the cell along the concentration gradient (high to low). NO energy required

Are transport proteins specialized?

Yes! A transport protein will recognize and move ONE type of molecule/ion based on the molecule’s shape/size/electrical charge

What is an example of a molecule that’s too big and needs a transport protein to help it across the cell membrane?

Glucose

What is active transport?

Movement of molecules/atoms/ions against concentration gradient AND using the cell’s energy (ATP)

What is another name for active transport?

Active transport pump- because the cell is using energy to pump the molecules through the membrane against the concentration gradient

A cell uses active transport for what?

To maintain an intracellular environment that is different from the environment outside the cell

What different thing does active transport allow?

Allows the cell to bring in nutrients and store them even if they’re in high concentration

Active transport is necessary for what?

Homeostasis (a constant internal environment is maintained despite changes in the eternal environment)

What is absolutely required by active transport?

Cellular energy! ATP!

What are the 3 steps of active transport using an ion as an example?

1. Ion drawn onto the transport protein

2. ATP moves the ion through the membrane

3. Ion is released inside where its concentration is higher

What is unique about the use of vesicles to move large molecules in/out?

Moves molecules without having to pass through the phospholipid bilayer

How do vesicles bring molecules into the cell?

Cell membrane folds in on itself to wrap around and seal large objects in a sac (vesicle).

Does the use of vesicles require energy?

Yes

What are 2 examples of large molecules that require the use of vesicles to enter the cell?

Proteins and polysaccharides

What are the 2 ways in which vesicles move materials across the cell membrane?

1. Endocytosis

2. Exocytosis

What is endocytosis?

The bringing of material into the cell. Cells ingest large materials. Portion of the cell membrane surrounds the material. “Pinched-in” portion breaks free from the cell membrane and forms a vesicle in the cytoplasm. Material can now travel to its final destination within the cell

What are the 3 types of endocytosis?

1. Phagocytosis

2. Pinocytosis

3. Receptor-mediated endocytosis

What is phagocytosis and its helpful “name”? Give an example

“Cell-eating”. Cell engulfs large solid particle; like an immune cell engulfing an invading bacteria to destroy it

What is pinocytosis and a helpful “name” for it? When does it occur?

“Cell-drinking”. When liquid droplets enter the cell (along with any small particles they may contain). Occurs in all cell types at all times

What is receptor-mediated endocytosis?

Enables the cell to acquire bulk quantities of substances. Molecules bind to receptor proteins located outside the cell membrane. Once enough molecules have gathered in an area, the cell membrane pinches in, forming the vesicle that will transport these molecules into the cell

What is exocytosis?

Takes material out of the cell. Vesicles export large molecules out of the cell, especially large waste particles

Give an example of exocytosis

Lysosomes break down wastes and toxins. Wastes are then transported out of the cell in a vesicle. Goes through the cytoplasm to fuse with the cell membrane. Membrane rearranges, opens, and releases the contents of the vesicle outside the cell

What would happen to a strip of potato after 24 hours in a glass of water?

Potato would absorb the water and increase in size

What would happen to a strip of potato after 24 hours in a glass of water and salt?

Potato would shrink

Which potato would show the most change- with just water or water and salt?

With salt. Greater osmotic potential in the salt glass

Which solution (just water or water and salt) is hypertonic and which is hypotonic?

Solution of just water is hypotonic; solution of water and salt was hypertonic

What would happen if the temperature was increased on the experiment with potato in a water glass and potato in a water and salt glass?

Rate of water leaving the potato would increase- increased motion of water molecules will increase the rate of diffusion of water

The phospholipid bilayer is made up of a hydrophilic head with a polar phosphate group. It loves water because water is also polar. Why?

Polar molecules are attracted to other polar molecules

How is cholesterol related to receptor-mediated endocytosis?

This method is how cholesterol enters the cell. If too much cholesterol is consumed in one’s diet, the receptors can’t handle it. Cholesterol builds up in arteries forming plaque. Can block blood vessels causing heart disease