THE CELL

Anindyaningrum Chrisant Rystiasih

Nadia Karlina

FT 7 - 2009

The Discovery of CellsI. Robert Hooke (1665), described chambers in cork; called them cells (cellulae) II. Anton van Leeuwenhoek (1665-1675),

A. The first to describe living single cells; results were checked and confirmed by HookeB. Saw “animalcules” in pond water using the scopes that he made

III. 1830s - full & widespread importance of cells realizedA. Matthias Schleiden,realized that, despite differences in tissue structures, all

plant tissues were made of cells & that plant embryos arise from single cellB. Theodor Schwann, realized cellular basis of animal life; concluded that plants &

animals are similar structuresC. Schwann then proposed first two tenets of Cell Theory1. All organisms are composed of one or more cells.2. The cell is the structural unit of life for all organisms.D. Rudolf Virchow, made good case for & added third tenet of Cell Theory derived

from his cell division observations; Cells can arise only by division from a preexisting cell.

Miller ExperimentReplicate conditions of Earth’s Primitive atmosphere

•Little/no free oxygen

•Mostly CO2 & N2

•Also H2, H2S & CO

(PLUS) Energy: Sunlight/ Electrical Discharge

(EQUALS) Organic Molecules

First cell is presumed to be self replicating RNA in phospholipid membrane.

Basic Properties of Cells • I. Life – most basic property of cells; they are the smallest units to exhibit this

property

• II. Cells are highly complex and organizedEach level of structure in cells has a great level of consistency from cell to cell :Organelles have consistent macromolecular composition arranged in a predictable patternCell structure is similar from organism to organism despite differences in higher anatomical features

• III. Cells possess genetic program & the means to use it (a blueprint); encoded in collection of genes

• IV. Cells are capable of producing more of themselves - mitosis and meiosis

• V. Cells acquire & use energy (constant input) to develop & maintain complexity – photosynthesis, respiration

Source of all energy needed by life on Earth arrives from sunSunlight trapped by light-absorbing pigments in photosynthetic cells Chemically stored as energy-rich carbohydrates Eaten by animals glucose disassembled; most of its energy is stored as ATP & used to run cell activities

Basic Properties of Cells Contd.

• VI. Cells carry out a variety of chemical reactions - sum total of chemical reactions in cells (metabolism); to do this, cells require enzymes (molecules that greatly increase rate of chemical reactions)

• VII. Cells engage in numerous mechanical activities (require constant energy to keep working):

A. Material moved from place to placeB. Structures assembled and disassembledC. Cells move from place to place

• VIII. Cells able to respond to stimuli whether organisms are uni- or multi cellular - have receptors that sense environment & initiate responses (move away from object in path or toward nutrient source)

• IX. Cells are capable of self-regulationA. Importance of regulatory mechanisms most evident when they break down

1. Failure of cell to correct error in DNA replication -> may lead to debilitating mutation2. Breakdown in growth control -> may lead to cancer cell & maybe death of whole organism

Eukaryotic Animal Cell

Eukaryotic Plant Cell

Eukaryotic Cell Cycle

• M, G1, S, G2• M mitosis (usually followed by cytokinesis)• S DNA replication• G1 Gap 1 metabolically active and

continuously grow• G2 Gap 2 growth continues, protein are

synthesis for preparation of mitosis

Why are most cells so small?

• A. Most eukaryotic cells have single nucleus with only 2 copies of most genes 1. Thus, cells can only produce limited number of mRNAs in a given amount of time 2. The larger a cell's volume, the longer it takes to make the number of mRNAs the cell needs

• B. Surface area/volume ratio which affects ability to exchange molecules.

Large cell=Small surface area/volume ratio --> surface area is not sufficient to take up substances needed to support metabolism (oxygen, nutrients, etc.) or get rid of wastes

• C. Cells depend on diffusionAs cell becomes larger, distance from surface to interior gets larger; diffusion time required to move things in & out of a metabolically active cell becomes too long

Larger Cells Have Strategies• Increase Surface Area

Eg. Intestinal epithelium which absorbs solutes have microvilli .

• Decrease cell metabolically active areaEg. interior of large plant cell is typically filled by large, fluid-filled vacuole rather than metabolically active cytoplasm

• 4. Giraffe (and other large animal) nerve cells - very long but very small diameter

Stem Cells

• A cell that divides to produce daughter cells that can either differentiate or remain as stem cells

• Source for production of differentiated cells throughout life eg. Blood cells, epithelial cells of skin, epithelial cells of digestive tract (all of which have short life span)

Embryonic Stem Cells

• Can differentiate into any type of cellEg. Cell-nuclear replacement or "therapeutic cloning"

This is Adult Stem Cell

Cell Communication

• Direct cell to cell ex: embryonic development, maintainance adult

tissue• Indirect

– Endocrine signaling (hormone, eg: estrogen) – Paracrine signaling (molecule release on one cell and acts

on neighboring target cell, eg: response of vertebrate immune system cells to foreign antigens)

Cell Death & Renewal

• Apoptosis, programmed cell death• Active Process, maintenance of embryonic

development and adult tissues• Apoptotic cells and fragments removes by

phagocytosis• Effector: caspases enzyme• Major caspases in Mamalian cells is

apoptosome complex (+ cytocrom C from Mytochondria)

Q U I Z ! ! !

• Please Prepare a Sheet of Paper• We will now test if you have been paying

attention.

• What is the smallest unit of Living Things?

CELL

• The Ovum is the largest …… while the smallest is the sperm ….

CELL

CELL

• Organisms are called Multicellular Organisms because they consist of multiple number of…?

A. tissuesB. organsC. cells

• What is a single space in an Excel sheet called?

CELL

• Fill in the dots:

• The longest …… in the human body is the motor neuron cell located in the spinal chord, near the central nervous system.

CELL

• There are more nerve ….. In your brain than stars in the milky way.

CELL

Reference

• http://www.answersingenesis.org/tj/images/v18/i2/abiogenesis_experiment.jpg

• Cooper, Geoffrey M. Hausman, Robert E. The Cell. A Molecular Approach. Fourth Edition. Washington, DC. 2007.

• easyweb.easynet.co.uk/~sfl/rlb_stem.htm