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The Cell. A cell is the smallest unit of living matter. Don’t confuse this with: atom, element, proton, etc. Cell Size. Three Main Parts. Plasma membrane Nucleus Cytoplasm. These are ALL CELLS!. Cell Theory. “Theory” is not a casual term in science.
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The Cell • A cell is the smallest unit of living matter. • Don’t confuse this with: atom, element, proton, etc.
Three Main Parts • Plasma membrane • Nucleus • Cytoplasm
Cell Theory • “Theory” is not a casual term in science. • Tested innumerable times with consistent results. • Universally accepted • One of the most basic, fundamental concepts in the foundation of biology.
Cell Theory • 1800s; several scientists working independently had similar results. 1. All organisms are made of cells. 2. A cell is the structural & function unit of organs. 3. All cells come from pre-existing cells. 4. Cells are capable of self-reproduction.
There are two types of cells: • Prokaryotic- cells that DO NOT have a nucleus or other cell ORGANELLES • Eukaryotic- cells with a NUCLEUS & cell ORGANELLES • Which is more complicated? • REMEMBER YOU ARE EUKARYOTIC!
Pro = before Karyote=kernel(nucleus) DNA is NOT contained within a nucleus Most have a cell wall outside the plasma membrane May have type of flagella or pilus Archaea and Bacteria Eu= true Karyote=nucleus DNA contained in double membraned nucleus Only plant cells have cell wall Contains membrane bound organelles Plants, animals, protists, fungi Prokaryotic vs Eukaryotic
Types of Organisms • Unicellular organisms • Bacteria, Protists, etc. • Multicellular organisms • Plants • Animals • Muscles, skin, nerves, liver, digestive, bones, blood, immune system, lungs, etc.
Why cells aren’t bigger • If cells get too large in volume compared to their surface area then it’s difficult to distribute nutrients throughout the cell and too hard to get rid of build up of wastes.
The Cell Membrane A phospholipid bilayer With proteins embedded in it
Hydrophillic heads and Hydrophobic tails • The phospholipid consists of hydrophilic heads, which point towards the outside environment and the cytoplasm. The hydrophobic tails repel the water and point in. Thus, the phospholipids form a bilayer that acts like a barrier between the cell and the environment. The phospholipid bilayer also contains cholesterol, which makes the bilayer stronger, more flexible and more permeable. There are a number of important proteins in the plasma membrane
Fluid Mosaic Model of the Cell Membrane • The purpose of the membrane is to control what goes in and out of the cell. • Semi-permeablemeans certain molecules can be transported across the membrane while others are kept out. • Proteins that are found in the bilayer are receptor proteins, which deal with communication, recognition proteins and transport proteins that regulate the movement of water and soluble molecules through the membrane.
Transport of molecules across the membrane • Transport is either active or passive. • Active transport is moving molecules against the concentration gradient and energy is required in the form of ATP. • Passive transport is moving molecules down the concentration gradient and no energy is required. • diffusion, which moves from high concentration to low concentration • osmosis, which is the diffusion of water molecules
Cell membrane interactive • cell membrane interactive • file:///C:/Documents%20and%20Settings/nancy/My%20Documents/tdc02_int_membraneweb/tdc02_int_membraneweb.htmlfile:///C:/Documents%20and%20Settings/nancy/My%20Documents/tdc02_int_membraneweb/tdc02_int_membraneweb.html
The Organelles • ..\Desktop\tdc02_vid_organelles.zip
Nucleus • cellular control center • Controls cellular activity • contains hereditary material (DNA in chromosomes) • self duplicating structure -divides when the cell divides
Structure of Nucleus • Nuclear Envelope (membrane): • Double lipid bilayer: keeps DNA separated from the rest of the cell • Continuous with Endoplasmic Reticulum • Nucleolus: assembly of ribosomes for protein synthesis • Nuclear pores: holes that allow stuff in and out
Rough Endoplasmic Reticulum • “HIGHWAY” for cell transport • consists of a network of interconnected, flattened sacs whose walls are formed of a single membrane. The outer surface is "rough" because it is studded with small particles called ribosomes. • The ribosomes synthesize proteins and discharge them into the sacs where they are packaged in membranes which travel through the cytoplasm to other organelles……. • (GOLGI BODIES) where they are further processed.
Golgi Bodies • Add carbohydrates component to the protein and package the finished product before it leaves the cell. • Form the plasma membrane and membranes of lysosomes
Lysomes • produced by the Golgi apparatus • contain powerful protein digesting enzymes • responsible for the breakdown and absorption of materials taken in by the cell. • Often, a cell engulfs a foreign substance through ENDOCYTOSIS, another form of active transport. During endocytosis, the cell membrane puckers up, forms a pouch around materials outside the cell, and pinches off to become a vesicle. If the contents need to be destroyed, lysosomes combine with the vesicle and release their enzymes.
vacuoles • fluid-filled, membrane-surrounded cavities inside a cell. The vacuole fills with food being digested and waste material that is on its way out of the cell. • removing unwanted structural debris surrounding the cell • sequestering materials that might be toxic to the cell • containment of waste products • maintaining internal hydrostatic pressure or turgor within the cell (especially plant cells) • storing small molecules • exporting unwanted substances from the cell.
Mitochondria • Mitochondria are the cells' power sources. • They are distinct organelles with two membranes. • Usually they are rod-shaped, however they can be round. • The outer membrane limits the organelle. • The inner membrane is thrown into folds or shelves that project inward. These are called "cristae mitochondriales • Contain their own DNA which can be passed on
Endosymbiosis • It is theorized that mitochondria and chloroplasts were once free living bacteria that got caught in evolution • Both are double membraned, contain their own DNA and can self replicate
Quick check • What is meant by the phrase "the cell is the functional unit of life"? • How are the organelles in a cell like the organs in a human body? • Why do you think cells that produce large numbers of proteins have more rough endoplasmic reticulum (ER) than cells that produce fewer proteins? • In which kinds of human cells would you expect to find the most mitochondria? The most lysosomes? The most ribosomes? Explain your answers.
Centrioles • Found only in animal cells, these paired organelles are typically located together near the nucleus, • centrioles are positioned so that they are at right angles to each other, Each centriole is made of nine bundles of microtubules (three per bundle) arranged in a ring. • Centrioles play a notable role in cell division.
cytoskeleton • ELEMENTS OF THE CYTOSKELETONAll of the microfilaments and microtubules combine to form the cytoskeleton of the cell. • The cytoskeleton is different from cytoplasm. The cytoskeleton provides structure. Cytoplasm is just a fluid. • The cytoskeleton connects to every organelle and every part of the membrane. Think about an amoeba. All of the pieces work together so that the foot might reach out towards the food. Then the lysosomes and peroxisomes are sent to begin digestion. The movement of the organelles and cytoplasm is all related to the tubules.
Plant cell wall • rigidity of the cell wall renders plants sedentary • Made of Cellulose • animals lack of wall allows their cells more flexibility, which is necessary for locomotion. • protects the intracellular contents • provides a porous medium for the circulation and distribution of water, minerals, and other nutrients, and • houses specialized molecules that regulate growth and protect the plant from disease.
Cell wall • The main chemical components of the primary plant cell wall include cellulose (in the form of organized microfibrils; a complex carbohydrate made up of several thousand glucose molecules linked end to end.
