Ch 3 Cell Physiology

Chapter 3

Cell Physiology

•Membrane Transport-Passive-Active

•Cell Cycle•Protein Synthesis

Do you remember learning about?

Membrane TransportMembrane Transport Movement into and out of cells to maintain HOMEOSTASIS

Solutions and TransportSolutions and Transport Solution – homogeneous mixture of two

or more components

- Solvent – dissolving medium

- Solutes – what gets dissolved (ex. Sugar,salt)

Intracellular fluid

- inside cell

- nucleoplasm & cytosol

Interstitial fluid

- fluid on the exterior of the cell

Passive ProcessesPassive ProcessesDiffusion

Particles distribute themselves evenly within a solution due to random molecular movement

Movement is from high concentration to low concentration, or down a concentration gradient

• http://www.youtube.com/watch?v=o6nqYcrItiQ&feature=related

Membrane is Selective PermeabilityMembrane is Selective Permeability Allows some materials to pass, not all

3 types of diffusion: depends on solute, size & charge

- Simple diffusion - lipid-soluble materials or small enough to pass through membrane pores

- Facilitated diffusion - too big or not lipid-soluble; requires protein carriers

- Osmosis - movement of water across membrane

Study the diagram below. It represents a container that is divided by a semi permeable membrane. A different solution in its initial state is shown on each side of the membrane.

Study the diagram below. It represents a container that is divided by a semi permeable membrane. A different solution in its initial state is shown on each side of the membrane.

1. Which substance(s) can move through the membrane? Why?2. Which direction will the molecule(s) will move? To side I or II?3. Which substance will move across fastest?4. How long will the molecule(s) will continue to move?

Osmosis - How Cells Respond to Osmosis - How Cells Respond to

Different SolutionsDifferent Solutions

90% H2O10% solute

90% H2O10% solute

90% H2O10% solute

90% H2O10% solute

85% H2O15% solute

95% H2O5% solute

Isotonic(no net movement

of water)

Hypotonic Hypertonic

What solution would you give someone who is retaining water?

Why shouldn’t you drink ocean water if you are thirsty?

Another Passive ProcessAnother Passive ProcessFiltration

Water and solutes are forced through a membrane by fluid, or pressure

Pressure gradient must exist

Solute-containing fluid is pushed from a high pressure area to lower pressure area

Happens in kidneys.

Active Transport ProcessesActive Transport Processes Transport substances that can’t pass because:

- too large

- not lipid-soluble

- going against concentration gradient

2 common forms of active transport

- Solute pumping

- Bulk transport

Energy (ATP)

required!

Solute pumpingSolute pumping Amino acids, some sugars and ions are

transported by solute pumps

ATP energizes protein carriers, and in most cases, moves substances against concentration gradients

Sodium-PotassiumPumps

Bulk TransportBulk TransportExocytosis Moves materials out of cell in vesicle

Vesicle combines with plasma membrane

Material is emptied to the outside

Endocytosis

Substances engulfed by being enclosed in a membranous vesicle

2 Types

- Phagocytosis – cell eating

- Pinocytosis – cell drinking

Cell Life CycleCell Life Cycle Interphase - cell

grows, DNA replication (G1, S, G2)

Mitosis - division of nucleus

Cytokinesis - division of cytoplasm

DNA ReplicationDNA Replication

The DNA is duplicated

Occurs at the end of interphase

DNA uncoils and each side serves as a template

Mitosis & Mitosis & CytokinesisCytokinesis

- Prophase - Centromeres migrate to poles; chromosomes become visible

Metaphase - Spindle fibers attach to chromosomes that are aligned in the middle of cell

Anaphase - Daughter chromosomes pulled toward poles

Telophase - Daughter nuclei seen; cleavage furrow seen

Cytokinesis - Division of cytoplasm; results in 2 identical daughter cells

Protein SynthesisProtein Synthesis

(Translation and Gene Expression)(Translation and Gene Expression)

Reading a gene to make a protein

-Gene - DNA segment that carries a blueprint for building one protein

-Proteins - for building or for enzymes

• 2 Major Processes:• Transcription - copying gene from

DNA to mRNA

• Translation - reading mRNA and linking amino acids together in the ribosome

Role of 3 Types of RNARole of 3 Types of RNA Messenger RNA (mRNA) -

copy of gene; made in nucleus & moved out to ribosome; holds codes for amino acids to make protein

Ribosomal RNA (rRNA) - helps form ribosomes

Transfer RNA (tRNA) - Transfers appropriate amino acids to the ribosome for building the protein

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