cellular transport and the cell cycle unit 3 chapter 8

Cellular Transport and the Cell Cycle

Unit 3

Chapter 8

Different ways of transporting materials across a cell membrane

1. Passive transport1. Diffusion

2. Osmosis: water diffusion

3. Facilitated transport

2. Active transport

3. Exocytosis

4. Endocytosis

Cells in isotonic solutions

Cell loses and gains water at an equal rate.

Net change to cell = nothing

Isotonic solution

Not ideal for plant cells because the cells become flaccid (limp)

Ideal for animal cells or cells without cell walls

Cells in a hypotonic solution

More water moves into the cell than moves out.

Net change = cell mass increases

Hypotonic solution

Ideal for plant cell where the cell becomes turgid (swollen)

Not ideal for animal cells where the cell lyses (bursts)

Cells in a hypertonic solution

More water moves out of the cell than moves in

Net change = cell mass decreases

Hypertonic solution

Not ideal for any cell Both shrink.

Passive transport

Movement of materials across a cell membrane in the direction of higher concentration to lower concentration

No ATP energy required

Passive transport by proteins

Facilitated transport

Movement of chemicals down a chemical gradient (from high to low concentration) through a protein

Passive transport

Channel vs. carrier proteins

Click on image to view video.

Active transport

Requires energy to move substances across the membrane against the concentration gradient (from lower to higher concentration)

Click on image to view video.

Exocytosis: transport of large particles out of cell

Endocytosis: transport of large particles inside of a cell

Cell reproduction: making new cells by a process called cell division

Cell cycle: sequence of growth and division of a cell

Step 1: Interphase (G1, S, G2)

Step 2: Mitosis and Cytokinesis (M)

Eukaryotic chromosome structure

Double helix coiled and twisted into a condensed structure

Bacterial DNA differs in that it is circular and not linear.

Step 1: Interphase

Grows in size Copies DNA

Each chromosome makes a copy, and the two resulting chromosomes are joined at the centromere.

Step 2: Mitosis (nuclear division)

Prophase Metaphase Anaphase Telophase

Prophase: spindle fibers extend, nuclear membrane disintegrates

Metaphase: chromosomes aligned along the middle

Anaphase: chromosomes pulled apart when spindle fibers become shorter

Telophase: two nucleus form at each pole of the cell

Cytokinesis: forming two daughter cells identical to the parent cell Animal cells:

cell pinches down the middle

Plant cells: cell plate forms to make new cell wall

Onion root tip showing phases of mitosis

The cell cycle

Click on image to view video.