the cell theory › 1500’s – europeans used lens to look at cloth quality › 1600’s – two...

The Cell Theory› 1500’s – Europeans used lens to look at cloth

quality› 1600’s – two useful instruments were made

with lens from the 1500’s Microscope Telescope Leeuwenhoek was the first to study nature under

a microscope› 1665 – Hooke used the first light microscope to

look at plant tissue Looked at cork Found the cells are the basic unit of life

Cell Theory› 1838 – Schelldon found all plants are made of

cells› 1829 – Schwann found that all animals are

made of cells› 1855 Virchow found cells come from cells› 1931 – Plowe found cells have cell membrane

that is a physical structure between cells› 1970 – Maegulis proposes theory of tiny

organelles in the cell once were free living cells

Cell theory states› All living things are composed of cells

› Cells are the basic structure and function in living things

› New cells are produced from existing cells

Cells come in many shape and sizes› Typical cell 5 to 50 micrometers in diameter› The tiniest bacteria are only 0.2 micrometer across and

hard to see with the most powerful light microscope› Chaos chaos a giant bacteria is 1000 micrometers and

can be seen with naked eye

Common structures in most cells› Cell membrane› Cell wall› Nucleus› cytoplasm

2 categories of cells› Prokaryotes –

smaller and simpler cells No nuclear membrane (genetic material dispersed throughout

cytoplasm) Cell membrane prokaryotic DNA is circular (it has no ends). Cytoplasm No membrane-bound organelles All bacteria Escherichia coli lives in your intestine Carries out every activity associated with life

Grow Reproduce Respond to stimulus Move sometime during their life cycle

Eukaryotes› Contain a nucleus, cell membrane, and

cytoplasm› Most contain organelles

Specialized structures that perform important cellular functions

› Some single cell organism› Most are Multicellular organisms› Eukaryotic DNA is linear

Pro vs. Eu

Eukaryotic Cell Structure

Organelles – little organs› Structures that are specialized for certain

processes

2 major parts of a cell› Nucleus › Cytoplasm


Cytoplasm – › Cytoplasm is basically the substance that fills the

cell. › It is a jelly-like material that is eighty percent water

and usually clear in color. › It is more like a viscous (thick) gel than a watery

substance, but it liquefies when shaken or stirred. › Cytoplasm, which can also be referred to as

cytosol, means cell substance. › The cytoplasm is the site where most cellular

activities occur, such as many metabolic pathways like glycolysis, and processes such as cell division.


Nucleus - also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. › It contains most of the cell's genetic material,

organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes.

› Nuclear envelope - a double membrane that encloses the entire organelle and separates its contents from the cellular cytoplasm and is dotted with pores which allow material to flow in and out

› Chromatin – granular material consisting of DNA bound to a protein.


Nucleus› Chromosomes – condensed chromatins

Happens when cells divide Distinct threadlike structures containing

genetic information

› Nucleolus – small, dense region where ribosomes are formed


Ribosomes - the components of cells that make proteins from amino acids. › Small particles of proteins and RNA found

throughout the cytoplasm› Considered a small machine in a large

factory producing proteins› Cells active in producing proteins are often

packed with ribsomes


Endoplasmic Reticulum – › responsible for the production of the protein and

lipid components of most of the cell's organelles. › The ER contains a great amount of folds - but the

membrane forms a single sheet enclosing a single closed sac.

› This internal space is called the ER lumen. › The ER is additionally responsible for moving

proteins and other carbohydrates to the Golgi apparatus, to the plasma membrane, to the lysosomes, or wherever else needed.


Endoplasmic Reticulum –› There are two types of ER - rough, which is coated

with ribosomes, and smooth, which isn't. › Rough ER is the site of protein synthesis. › The smooth ER is where the vesicles carrying

newly synthesized proteins (from the rough ER) are budded off

› Uses enzymes to in the synthesis of lipid membranes and detoxification of drugs The liver cells play a role in detoxification and contain

large amounts of ER


Golgi Apparatus – › The Golgi complex contains a great number of

vesicles. These vesicles are used to send molecules to the

cellular membrane, where they are excreted. › There are also larger secretory vesicles, which are

used for selective excretion. › The Golgi is principally responsible for directing

molecular traffic in the cell› nearly all molecules pass through the Golgi

complex at some point in their existence. The sorting is mediated by the vesicles. When proteins bind with their appropriate receptor on

the vesicle, they are encoated in the vesicle and transported away.


Lysosome› The lysosome is a membranous bag which

contains hydrolytic enzymes that are used to digest macromolecules.

› The lysosome contains over 40 enzymes


Vacuoles – › used only in plant cells. › It is responsible for maintaining the shape and

structure of the cell. › Plant cells don't increase in size by expanding the

cytoplasm, rather they increase the size of their vacuoles.

› The vacuole is a large vesicle which is also used to store nutrients, metabolites, and waste products.

› The pressure applied by the vacuole, called turgor, is necessary to maintain the size of the cell.


Chloroplast –› The chloroplast, basically, is the organelle

responsible for photosynthesis. › Structurally it is very similar to the mitochondrion. › It contains a permeable outer membrane, a less

permeable inner membrane, a intermembrane space, and an inner section called the stroma.

› However, the chloroplast is larger than the mitochondria

› Unlike other organelles, chloroplast and mitochondria have their own DNA.


Mitochondria – › Converts chemical energy stored in food

into compounds that are more convenient for the cell to use

› The powerhouse of the cell› The mitochondrion consists of four major

sections – the outer membrane, the intermembrane space, the inner membrane, and the matrix.


Mitochondria – › The Outer Membrane -This membrane contains a

great number of large transport proteins, which allows for large molecules to enter with ease. This membrane includes proteins that can convert lipid substrates into forms that can be used by the matrix.

› Inner membrane space - This space contains enzymes› Inner membrane - This membrane is highly convoluted,

forming many folds called cristae. This serves to greatly increase the surface area, allowing more work to be done is a smaller space

› Matrix - The Krebs Cycle takes place here. It also contains several copies of the mitochondrial DNA genome, special mitochondrial ribosome's, tRNAs, and various enzymes required for the expression of the mitochondrial gene


Cytoskeleton – › Eukaryotic cells have a wide variety of distinct

shapes and internal organizations. › Cells are capable of changing their shape, moving

organelles, and in many cases, move from place to place. This requires a network a protein filaments placed in the cytoplasm known as the cytoskeleton.

› The two most important protein filaments are called the actin filaments and the microtubules. The actin is responsible for contraction (like in

muscles) and the microtubules are for structural strength

Cell Boundaries

Cell membrane – › cell membrane is a flexible lipid bilayer. › The lipid molecules (mostly phospholipids) that

make up the membrane have a polar, hydrophilic head and two hydrophobic hydrocarbon tails.

› When the lipids are immersed in an aqueous solution the lipids spontaneously bury the tails together and leave the hydrophilic heads exposed. Thus this is a handy membrane to use, because it can

automatically fix itself when torn

Cell Boundaries

Cell Boundaries

Cell Walls – › It provides the most significant difference between

plant cells and other eukaryotic cells. › The cell wall is rigid (up to many micrometers in

thickness) and gives plant cells a very defined shape. › The cell wall is composed of cellulose fiber,

polysaccharides, and proteins. › In new cells the cell wall is thin and not very rigid.

This allows the young cell to grow. This first cell wall of these growing cells is called the

primary cell wall. When the cell is fully grown, it may retain its primary wall, sometimes thickening it, or it may deposit new layers of a different material, called the secondary cell wall.

Cell Boundaries

Cell Boundaries

Diffusion - the process by which molecules spread from areas of high concentration, to areas of low concentration. › When the molecules are even throughout a space -

it is called EQUILIBRIUM Concentration gradient - a difference

between concentrations in a space. Equilibrium – concentration throughout a

solution is the same Diffusion depends upon random particle

movements, substances diffuse across membranes without requiring the cell to use energy

Cell Boundaries

Cell Boundaries

Osmosis – › The diffusion of water (across a

membrane) through a selectively permeable membrane

› Water will move in the direction where there is a high concentration of solute and hence a lower concentration of water.

Cell Boundaries

Cell Boundaries

Isotonic – › A solution that contains the same concentration of

solute as an another solution (e.g. the cell's cytoplasm). › When a cell is placed in an isotonic solution, the water

diffuses into and out of the cell at the same rate. The

fluid that surrounds the body cells is isotonic.

Cell Boundaries

Hypertonic solution – › contain a high

concentration of solute relative to another solution (e.g. the cell's cytoplasm).

› When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel

Cell Boundaries

Hypotonic solution – › contain a low

concentration of solute relative to another solution (e.g. the cell's cytoplasm).

› When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode.

Cell Boundaries

Cell Boundaries

Osmotic pressure –› The pressure that must be applied to a

solution to prevent the inward flow of water across a semi permeable membrane

Cell Boundaries

Facilitated Diffusion –› Glucose, sodium ions and chloride ions are

just a few examples of molecules and ions that must get across the plasma membrane but to which the lipid bilayer of the membrane is virtually impermeable.

› Their transport must therefore be "facilitated" by proteins that span the membrane and provide an alternative route or bypass.

› Facilitated diffusion

Cell Boundaries

Active Transport – › Active Transport - When cells must move

materials in an opposite direction - against a concentration gradient. It requires Energy.

› Proteins or Pumps are found in the cell membrane transport molecules across the membrane.

Cell Boundaries

Molecular transport – › Proteins are used to move small molecules such as

calcium, potassium, and sodium ions across the membrane Endocytosis - cell takes in large particles by engulfing

them Phagocytosis - "cell eating" - extensions off cytoplasm

surround a particle and package it within a food vacuole and then the cell engulfs it. Ex. Amoebas use this process.

Pinocytosis - the process of taking up liquid from the surrounding environment. Tiny pockets form along the membrane, fill with liquid, and pinch off.

Exocytosis - cell gets rid of particles, opposite of endocytosis

Cell Boundaries

The Diversity of Cellular Life

Unicellular organisms – › Single cell organism› Do all things that you expect living things

to do Grow, respond to surrounding, transform

energy and reproduce Multicellular organisms –

› Organisms made of many cells› Organism can develop different ways to

perform tasks.


Specialized cells – › Red blood cells – transport oxygen by

binding oxygen to a specific protein› Pancreas produces special enzymes to

make it possible to digest food› Muscle cells give use the ability to move.› Guard cells in a plant open and close to the

outside depending on the condition of the plant. Example – gas exchange or transpiration


Level of organization› Cells

basic structural and functional unit of all known living organisms.

It is the smallest unit of life that is classified as a living thing

› Tissue – similar cells grouped together› Organs – groups of tissues that work

together› Organ System – a group of organs that work

together for a specific propose

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