Cells OverviewChapter 3 for Anatomy Chapter 7 for Biology

Life is Cellular

A cluster of neural cells were derived from human embryonic stem cells in the lab. The motor neurons are shown in red; neural fibers appear green and the blue

specks indicate DNA in cell nuclei.

Microscopes

• Mid 1600s

• 1665 Robert Hooke

• 1st Compound Microscope

• After looking at Cork

• Saw cambers called Cells

• Anton Van Leeuwenhoek

• Pond water (animalcules)

Cork Cells / Microscopic Animals

• Cork Cells at 100X Magnification / Plankton have limited powers of locomotion

Scanning Electron Microscope

• SEM is a type of electron microscope that images the samples surface by scanning it with a high-energy beam of electrons.

Transmission Electron Microscope

• TEM uses a beam of highly energetic electrons to examine objects very closely, on a fine scale. A TEM shines a beam of electrons through an object.

Scanning Probe Microscope

• SPM is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen.

Cell theory

• All organisms are comprised of more than one cell

• Cell is the basic unit of life

• All cells come from preexisting cells

What is an organelle?

Membrane bound structures with particular functions within eukaryotic cells

Types of Organelles

• Nucleus• Cell membrane• Ribosomes• Endoplasmic reticulum• Golgi Apparatus• Lysosomes• Vacuoles• Mitochondria• Chloroplast – Plants only• Cell wall – plants only • Cytoskeleton

Bacteria cell

Cell Wall

• The rigid cell wall of plants is made of fibrils of cellulose embedded in a matrix of several other kinds of polymers

• Bacteria cell wall is made up of polysaccharides and protein.

Chloroplast

• Captures light energy in plants and produces ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.

Endoplasmic Reticulum

• Synthesis of protein and lipids– Rough ER – protein synthesis – can exsist in

cytoplasm– Smooth ER – lipid synthesis

Ribosomes• Sites of protein synthesis

• Scattered throughout cytoplasm

• Comprised of protein and RNA molecules

• Provide structural support for RNA during protein synthesis from amino acids

Golgi Bodies• Composed of six flattened membranous

sacs

• Packages and delivers proteins synthesized by ribosomes

• Proteins arrive at this spot in vesicles, where glycoproteins are to be received

Golgi Bodies• They pass through one end and continue

to pass over the sac until the protein is chemically processed

• When the altered glycoprotein reaches outermost layer, then bubblelike structures form and move throughout the cell membrane – exocytosis

Mitochondria• Elongated fluid filled sacs

• Move slowly through cytoplasm and reproduce by dividing

• Has inner and outer layers

Mitochondria• Inner layer has cristae that control some

chemical reactions, through enzymatic processes

• Chemical reactions release energy• Major site of ATP production – energy for

the cell

Lysosome• “garbage men” of the cell• Membranous sacs• Powerful enzymes that breakdown nutrient

molecules or foreign particles• In blood cells – can destroy bacteria• In cells in general – can breakdown dead

cell parts

Microfilaments• Tiny rods of actin protein that form

meshwork or bundles

• Provide cell mobility

• In muscle cells – they aggregate to form myofybrils, which help the cells to contract

Microtubules

• Long slender tubes with diameter two to three times that of microfilaments

• Composed of globular tubulin proteins – 9+2 array (9 outside, 2 inside)

Centrosome• Structure near Golgi Apparatus and

nucleus

• Consists of two hollow cylinders called centrioles

• Lie at right angles and distribute chromosomes evenly to new cells during mitosis.

Cilia

• Motile extensions from certain cells

• Comprised of microtubules in 9+2 array

• Tiny hairlike structures

• Move to and fro, in succession, so that there is a wavelike motion

Flagella • Motile extensions from certain cells

• Comprised of microtubules in 9+2 array

• A cell will only normally have one flagellum

• Swim motion

Vesicles• Or vacuoles• Membranous sacs formed by part of the

cell membrane folding inward and pinching off

• Material outside the cell is now inside and in the cytoplasm

Cell Nucleus• Houses genetic material• Enclosed in a double layer nuclear

envelope – inner and outer lipid bilayer membranes

• Protein-lined channels called nuclear pores that allow for certain molecules to exit

Nucleolus• Small dense body composed largely of

RNA and protein• No surrounding membrane• Forms in specialized regions of certain

chromosomes• Ribosomes form in the nucleolus and

move through nuclear pores to the cytoplasm

Chromatin• Loosely coiled fibers of DNA and proteins

= chromosomes

• DNA = information for protein synthesis

• Beginning of cell division – chromatin coil tightly and individual chromosomes become visible

Cell Membrane Structure

• A phospholipid consists of a – polar portion, called the head, – two longer fatty acids, called the tail.

Cell Membrane Structure

When mixed with water, the heads are attracted to the polar water molecules.

The nonpolar tails move as far from water as possible, and a double layer of phospholipids with tails to the interior results.

http://www.mhhe.com/biosci/esp/2002_general/Esp/default.htm

Phospholipid bi-layer of a cell membrane