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

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Active transport

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

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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

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