CellsHonors Human Anatomy and Physiology

Coach Denson

Introduction to CellCells are the structural and physiological unit of all living organisms.

A cell’s function is determined by its anatomy.

Nerve cells are very longEpithelial cells in the mouth are flat like floor tiles.Muscle cells are made of telescoping fibers that can contract.

Although cells vary greatly, they have some things in common. All the various parts make a composite cell.

Composite Cell

Three main parts in a eukaryotic cell.1. Cell Membrane• Functions:• Boundary of the cell• Controls entrance and exit to cell• Site of many metabolic reactions• Signal transduction

• Characteristics• Extremely thin (only 2 molecules thick)• Flexible• Somewhat elastic• Selectively permeable

Composite Cell• Structure• Double layer of phospholipids• Water soluble substances can’t pass• Lipid soluble substances pass

• Embedded proteins• Receptor proteins extend into and

out of the cell• Integral proteins form pores and

channels.• Peripheral proteins function as

enzymes.• Glycoproteins function in recognition

and binding.

Composite Cell• Intercellular Junctions• Tight junctions fuse adjacent cell

membranes.• Desmosomes join cells in “spot welds”• Gap Junctions connect with tiny tubes that

allow movement of materials.

2. Cytoplasm• Functions:• Support Organelles• Medium for diffusion• Provide dissolved materials for metabolism.

• Structure-Cytosol(fluid) and cytoskeleton(protein rod and tubule support)

• Organelles

Composite Cell: Organelles:• Endoplasmic Reticulum (ER)-Zig-zag

appearance in cell• Rough and Smooth (As as “Flow Control”• Structure-

• complex membrane tubes, canals, sacs; connect cell membrane and nucleus (Membrane Structure)

• Function-• Intracellular transport; provide surfaces for protein

synthesis and other metabolic reactions.

• Ribosomes• Structure-

• Protein (2) and RNA (2)

• Function-• Protein synthesis

Composite Cell: Organelles:• Golgi Apparatus• Structure-

• Stack of flattened membranous sacs (cisternae)

• Function-• Modify, package, deliver proteins produced by

ribosomes on rough ER for cellular export

• Mitochondria (~1700/Cell)• Structure-

• Double membrane; inner membrane consists of folds(cristae); non-chromosomal DNA; motile(moves on it’s own)

• Function-• Assist in releasing energy from glucose in the form

of ATP(cellular respiration)

Composite Cell: Organelles:• Lysosomes• Structure-

• Tiny, membranous sacs containing digestive enzymes; much variety of shape.

• Function-• Dismantle debris; destroy worn cell parts; break down

engulfed material.

• Peroxisomes (special type of lysosomes)• Structure-

• Tiny membranous sacs containing enzymes• (Peroxidase, Catalase) specific to the function.• Can break down hydrogen peroxide

• Function-• Regulate metabolic reactions that produce dangerous

by-products and then break down those by-products

Composite Cell: Organelles:• Centrosomes-made up of 2 centrioles-90 degrees to

each other• Structure-

• Nonmembranous; 2 cylinders (centrioles) of a protein microtubules at right angles; near the nucleus

• Function-• During cell division centrioles migrate to opposite

poles, form spindle fibers attached to chromosomes and assist in proper disjunction.

• Cilia and Flagella• Structure-• Found on the free surfaces of some cells;

distinct cylindrical patter of microtubules, attached to modified centrioles called basal bodies.

• Function-• Produce undulating motions for moving the cell

or moving material past the cell.

Composite Cell: Organelles:• Vesicles• Structure-

• Membranous sacs that vary in size and contents (i.e. lysosomes, peroxisomes, etc.)……enzymes.

• Function-• Storage; movement of particles and materials

• Microfilaments• Structure-

• Mesh or bundle of actin rods-made up of actin (also in muscles)

• Function-• Causes various kinds of internal movement in cells

Composite Cell: Organelles:• Microtubules-bigger than microfilaments,

made up of tubulin• Structure-

• Long, rigid tubes of tubulin

• Function-• Provides cytoskeletal framework

• Inclusions- not necessary for the cell to stay alive• Structure-

• bundle of chemicals that do not directly assist in the function/survival of the cell

• Function-• Temporary storage of chemicals (melanin, lipids,

etc)

Composite Cell3. Nucleus• Functions-

• Direct the activities of the cell• Safeguard DNA

• Structure• Relatively large, spherical• Nuclear envelope (phospholipid membrane)• Double Bilayer• Nuclear Pores-used for nucleotides to enter the

nucleus

• Nucleoulus• Nonmembranous• Site of ribosome production (RNA part)-where

ribosomal RNA is made.

Composite Cell• Nucleus continued….

• Chromatin• Loosely coiled DNA• Protein histones act as spools for

chromatin

Movement into and out of the cell

1.Diffusion

2.Osmosis

3.Filtration

4.Active Transport

5.Endocytosis/Exocytosis

Diffusion• Movement from greater

concentration to lesser concentration.

• Simple diffusion requires NO ENERGY

• Facilitated diffusion uses a carrier molecule to assist materials across the membrane.

Osmosis• Movement of water from relative greater

concentration of water to relative lesser concentration of water. (Selectively Permeable)• Isotonic solution-

• Water concentration is equal on both sides of cell membrane. Net movement=0

• Hypertonic solution-• Water is relatively less concentrated in the solution.

Water moves across the membrane out of the cell toward the hypertonic solution.

• Hypotonic solution-• Water is relatively more concentrated in the

solution.• Water moves across the membrane into the cell

away from the hypotonic solution.

Filtration• Movement of materials across a

membrane due to some force.• Blood pressure-causes blood to be

filtered.• Hydrostatic pressure

Active Transport• Opposite of diffusion

• Movement of materials from lower concentration to higher concentration

• Requires Energy (ATP)

• Pump Mechanisms

Endocytosis/Exocytosis• Movement of particles across a membrane, but

particles are encapsulated within a membrane vesicle.• Pinocytosis-

• Movement of water (“pino”-drink)• Membrane eventually breaks down inside cell and

releases water.

• Phagocytosis• Movement of food particles (“phago”-eat)• Lysosomes attach and break down material

• Receptor mediated Endocytosis• Protein molecules “receive” specific materials and

vesicles are formed around them.

Cell Cycle• Stages that a cell goes through from the time it

forms until it divides.

• Interphase- cell carries out its normal activity; DNA replicates

• Mitosis-genetic material divides (Nuclear Division)

• Cytokinesis- the rest of the cell divides

• Mitosis:• Prophase• Metaphase• Anaphase• Telophase

Mitosis

Cell division/ Nuclear division

Dividing chromosomes

Mitosis: Prophase• Chromatin (indistinguishable strands)

condenses into chromosomes (visible bodies)

• Nuclear membrane disintegrates

• Centrioles begin to migrate to opposite poles

Mitosis: Metaphase• Chromosomes line up on equator

between centrioles

• Spindle fibers form and attach to chromosome centromeres and centrioles.

Mitosis: Anaphase• Chromosomes are pulled apart to

opposite sides.

• Centrioles “reel” in chromosomes to opposite poles.

Mitosis: Telophase• Chromosomes begin to unravel into

chromatin

• Spindle fibers detach and disintegrate

• Nuclear membrane reforms around new nuclei

For Mitosis Know…

What’s going on in:The nuclear membraneCentriolesChromosomes

Cytoplasmic Division

• Cytokinesis• Cytoplasm divides

• Begins during anaphase; ends when two “new” daughter cells are formed.

Cellular Differentiation• Process of cells taking on special anatomy and

physiology• All cells go through this

• Stem cells have not differentiated yet.

Control of Cell Division• Loss of telomeres on the ends of chromosomes

triggers cell division to stop.

• Cell size-• cells reach a certain size and divides

• Presence of kinases and cyclins

• Hormones

• Local Growth Factor

• Space availability