Chap 8 .Cellular Transport and the Cell Cycle

• To help keep you healthy,

–materials must be transported through cell membranes, and

CHAPTER OBJECTIVES

• Be able to explain these processes :• diffusion, passive transport, active transport, endocytosis

and exocytosis.• Be able to explain why these are important to living cells• Be able to predict the effect of a hypertonic, hypotonic or

isotonic solution on a cell.• Be able to explain why cell size is limited• Be able to sequence the events of the cell cycle.• Be able to describe and illustrate the four stages of Mitosis• Be able to explain how the Cell Cycle is Regulated.• How are Cell Cycle Control and cancer related?

Section 8.1 Cellular Transport

1. Osmosis2. Passive Transport3. Active transport4.Endocytosis5.Exocytosis

Fig. 5.8, p. 80

Diffusion

Osmosis

•Diffusion of water molecules across a selectively permeable membrane

Water in cells

• In a cell, water always moves to balance concentration on both sides of the cell.

• Helps maintain Homeostasis

.• What affects osmosis?• Solids• solution:__________+ __________

• Concentration gradient: unequal distribution of ______ on both sides of a membrane.

Tonicity: Comparing solute concentrations

Isotonic solutions: equal

Hypertonic –moreHypotonic - less

Tonicity and Osmosis

2% sucrose

water 10% sucrose 2% sucrose

Fig. 5.23, p. 89

compartment1

HYPOTONICSOLUTION

membrane permeable towater but not to solutes

HYPERTONICSOLUTION

compartment2

fluid volume increasesIn compartment 2

There is a concentration gradient here

• .

Osmotic Pressure

• Water enters cell –swells• Exerts pressure on the cell

membrane

• How does a plant cell withstand this pressure?

• Animal cell?

WORK WITH YOUR SHOULDER PARTNER FOR THE NEXT 5-7 MIN TO ANSWER THE

FOLLOWING 6 QUESTIONS.1. What happens to cells (plant and animal) in a hypotonic solution?

2. Why does an animal cell burst?

3. What keeps a plant cell from bursting?

4. Why do plants wilt (hint, read p. 197 and 198)

5. What happens to cells (plant and animal) in a hypertonic solution?

6. What happens to cells (plant and animal) in an isotonic solution?

Follow directions for the foldable on p. 195

• Using your text-p. 197, draw pictures in your foldable of animal and plant cells in

• Isotonic solution

• Hypotonic solution

• Hypertonic solution

• Describe what is happening in each.

prepare a table in your notesType of Transport

Transport Protein Used?

Direction of Movement

Requires Energy Input From Cell?

Classification of Transport

(active/passive)

SIMPLE DIFFUSION

FACILITATED DIFFUSION

ACTIVE TRANSPORT

ENDOCYTOSIS

EXOCYTOSIS

Facilitated Duffusion

prepare a table in your notesType of Transport

Transport Protein Used?

Direction of Movement

Requires Energy Input From Cell?

Classification of Transport

(active/passive)

SIMPLE DIFFUSION

no High to low conc no passive

FACILITATED DIFFUSION

Yes

Channel or carrier

High to low conc no passive

ACTIVE TRANSPORT

ENDOCYTOSIS

EXOCYTOSIS

Yes, carrier (pump)

No

no

Low to high conc

Both

both

Yes

Yes

yes

Active

Neither

neither

2. Passive Transport

NO ENERGY NEEDED; DIFFUSION DOWN CONC. GRADIENT.

2 TYPES:• 1. Simple Diffusion: through lipid bilayer:

nonpolar (O2, CO2), water(small)

• 2. Facilitated Diffusion: using a transport protein—2 kinds: 1. Channel Proteins

2. Carrier Proteins (change shape)

Carrier Protein : Facilitated diffusion

solute

Active Transport•Solutes go against concentration gradient (from less conc. to more)

•Requires Energy

•Through a Carrier Protein (called a pump)

Active Transport• 1. Sodium Potassium Pump-Enables

cells to conduct nerve impulses

• 2. Proton Pumps—These are the key to cell metabolism—(mitochondria and chloroplasts)

animation

Transport of Large Particles: These both require energy.

•1. Endocytosis- a cell surrounds and brings in particles, or even whole cells.

2. Exocytosis-The expulsion or

secretion of materials from a cell.

EXOCYTOSIS

The vacuole formed moves inside the cell.

Section 8.2 Cell Growth and Reproduction

• Cell Size Limitations

• Why can’t you be just one BIG CELL??? 1.Diffusion– Within the cell nutrients and waste move by

__________• Not so effiecient over long distances!

More limitations…

• 2. DNA– Cell can’t survive unless there is enough of it to

support the protein needs.

– WHAT DOES DNA HAVE TO DO WITH PROTEINS ANYWAY?

Yet More Limitations!!

• 3. Surface area to volume ratio.– As a cell’s size increases, the volume increases

at a much faster rate than its surface area.

1 mm cube 2mm cube 4 mm cube

S.A

6x1x1= 6mm2 6 x 2x2=

V.

1mm 3

Mitosis

• A type of nuclear division.

• The process by which 2 daughter cells are formed, each containing a complete set of chromosomes.

1. Prophase• Longest phase• Chromatin coils to form visible

chromosomes• Nuclear envelope breaks apart• Nucleolus disappears

• Centrioles (in animals) migrate to opposite sides

• Spindle Forms; • Aster visible in animal cells.

MetaphaseSister chromatids become attached to spindle fibers at their centromere.

Sister Chromatids line up at spindle equator.

Anaphase

• Sister chromatids pulled apart

Telophase• Chromosomes

unwind—back into chromatin.

• New nuclear envelopes form around each set of chromatin.

CYTOKINESIS• Cytoplasmic division• Different in plants and animals• In Animals: a furrow forms and the cell pinches in 2

• In plants, a cell plate forms across the middle, them membranes, then cell walls.

Results of Mitosis

• 2 new cells with chromosomes that are identical to parent cell.

• Function identically to the parent cell.

Importance of Mitosis

• Single-celled organisms: reproduce this way.

• Multicellular organisms:– Enables formation of tissues and organs, and

organ systems

Section 8.3 CONTROL OF THE CELL CYCLE

2 types of proteins involved in control:

1. Controlled by cyclins ( a protein)

2. A type of enzyme activates the cyclin.

Together, this activated cyclin regulates the cell cycle.

Uncontrolled cell growth

• Tumor– 1. Benign

– 2. Malignant

Cancer

• Malignant tumor

• Results from uncontrolled cell division

• Cell cycle controls not functioning normally.

• Results from changes in one or more genes involved in production of proteins involved in the cell cycle.

• May metestasize: travel via blood to other parts of the body.

Causes

• Environmental

• Genetic

• Viral Infections (virus may damage genes)

Cancer Prevention

• A healthy diet• Fiber—reduce incidence

of colon cancer• Fat moderation• Vitamins A,C,E, bets

carotene (all antioxidants)

• Minerals: calcium

• Exercise

Fluid-Mosaic Model

Cell recognition protein

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..\unit 2 documents\animationsNa K pump.htm

Example: Glucagon

• In this role, glucagon is a Ligand

Fig. 5.24, p. 89

Protein Hormone binds with surface receptor

GLUCAGON-Why does it not just pass through the cell

membrane?

• Made of Protein—so it is

•Unable to pass through lipid layer.

• Binds with cell receptor, but does NOT enter cell.

Gated Channel

2. Voltage-Gated: Respond so change in

Electrical current:Sodium/Potassium- Nerve

Impulse Transmission

Fig. 5.25a, p. 91

P energyinput

low

high

Co

nce

ntr

atio

n g

rad

ien

t

DIFFUSION ACROSSLIPID BILAYER

PASSIVE TRANSPORTfacilitated diffusion

ACTIVETRANSPORT

lipid bilayer

Specific solutes pumped across, through transport proteins against gradient; requires energy boost

Water-soluble molecules and ions diffuse through interior of transport proteins. No energy boost required.

Lipid-solublemolecules and water molecules diffuse across

.

Cell Membrane Semi-permeable• Permeable to :Small molecules:

H2O, O2, CO2, hydrophobic molecules, small lipids

• Impermeable to : large polar molecules,ions K=, Na+, glucose, macromolecules, proteins, carbs., DNA

Diffusion

Movement of molecules from higher conc. to lower concentration until =