CELLS – Chapters 6, 7,

11, 12

Cell Structure, Membrane Function, Cell Communication and the Cell Cycle/Mitosis

CELLSare based on

Cell Theory

states that

1. all living things are made of cells

2. all cells come from other cells

3. Cells are the most basic unit of lifeCell

structures & function

Cell replication

Ch 6, 7, 11

Ch 12

Endomembrane System

• Secreted or membrane-bound proteins only

• (Free ribosomes synthesis soluble cytosolic proteins)

Cells are dynamic!

• Cell division & growth• Metabolism– Building proteins and other cell parts (anabolism)– Catabolism– Repair of damaged cell parts– Chemical reactions to stay alive and maintain

homeostasis• Cell communication

Membrane Structure & Function

Critical components of selectively permeable membrane

• Phospholipids – barrier• Cholesterol – regulates fluidity• Transmembrane proteins – render selectivity– Receptors– Ion channels– Aquaporins – allow water to pass into/out of cell– Transport proteins

• Outer leaflet – Carbohydrates – cell identification– Extracellular matrix (ECM) – interaction with surroundings

Types of molecular movement across the cell membrane

• Passive Transport–Diffusion– Facilitated Diffusion–Osmosis

• Active Transport• Bulk transport:

Endocytosis/Exocytosis/Pinocytosis

Terms to know:• Concentration gradient – a form of stored energy• Solute• Solvent• Isotonic• Hypertonic• Hypotonic• Equilibrium

Phrases to know• Passive transport

– Molecules move down/with their concentration gradient

– From high concentration to low concentration

• Active transport– Molecules move against

their concentration gradient– From low concentration to

high concentration– Requires input of ATP energy

from cell

Passive transport - DiffusionIn the absence of any partitions, molecules will move from an area of high concentration to an area of low concentration

Diffusion across a cell membrane• What types of molecules can cross the

membrane barrier freely?Molecules of dye Membrane

(a) Passive transport of one type of molecule

Equilibrium

(b) Passive transport of two types of molecules

Equilibrium

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

Passive transport - Facilitated Diffusion• Requires a protein channel• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

Passive transport - Osmosis• Movement of H2O through aquaporin proteins• Depends on water potential – the direction water molecules

will flow is determined by solute concentration on either side of the membrane

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

Remember secondary and tertiary structure???

Animalcell

Normal Lysing

Plasmolysis

Plantcell

Flaccid (wilts) Turgid (normal)

Plasmamembrane

(a) Isotonic solution (b) Hypotonic solution (c) Hypertonic solution

Shriveled

The effects of osmosis differ in plant and animal cells

Active Transport• Moves solutes against their concentration

gradient via a transport protein• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

Active transport – bulk transport via exocytosis, endocytosis & pinocytosis

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html

Receptor-mediated endocytosis

Receptor-mediated endocytosis: cholesterol uptake

http://bcs.whfreeman.com/thelifewire/content/chp05/0502003.html

Visual Summary 5.2

Cell Signaling

• Cells communicate with one another for several reasons– Growth– Development– Stimulate immune response– Regulate gene expression– Relay/transmit signals in nervous system– Fight or flight response– Homeostasis (example: regulate blood glucose)

Three stages of cell signaling• Reception, Transduction, Response• Animations: Ch 11

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__receptors_linked_to_a_channel_protein.html

Ch 12 – Mitosis & the Cell Cycle

Mitosis: duplicating cells• Occurs in somatic cells (body cells) throughout life– Wound healing– Growth– Repair/maintenance (skin, intestine, hair follicles,

replacement of uterine lining after menstruation)

Results of (normal) Mitosis

• 2 genetically identical cells (“daughter cells”)

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

Checkpoints regulate the cell cycle

Interplay of Cyclin and Cdk proteins regulates progression through the cell cycle

Normal cell division has 2 key characteristics:

• Density-dependent inhibition

• Anchorage dependency

• Cells that are not adhered to a surface will not proliferate

• Cells use cell signaling to detect growth factors and density signals