cell structure index cards

8/7/2019 Cell Structure Index Cards

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Erick Camacho CellStructure

Cell theory: the basic unit of structure

and function of all living organisms is the cell.

Virchows Theory (1855): all cells

arise from pre-existing cells by cell division.

Partially Permeable: refers to the

thin membrane surrounding all cells and

controls the exchange between the cell andits environment; allows a controlled traffic of

materials across it in both directions.

Light Microscope: uses light as a

source of radiation

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Electron Microscope: uses electrons

as a source of radiation.

Ultrastructure: the fine or detailed

structure of a cell as revealed by the electron

microscope.



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Similar Features of Plant and Different Features of Plant



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Animal Cells

Each cell is surrounded by aplasma membrane.

Each cell has a nucleus.Each cell has a mass of looselycoiled threads known aschromatin.

Both contain nucleolus, which ismade of loops of DNA fromseveral chromosomes.

Both contain cytoplasm, which isan aqueous material, varying inconsistency.

Both contain organelles, whichare defined as functionally andstructurally distinct parts of a cell.

Both contain mitochondria, which

specialize in aerobic respiration.Both contain the Golgi apparatus,which is part of a complex internal

and Animal Cells

The animal cell contains thecentriole, which specializes in

nuclear division. The plant cells are generallarger and are surrounded by acell wall outside the plasmamembrane.

The plant cell containsplasmodesmata, which links

neighboring plant cells.The plant cells also contain alarge central vacuole andchloroplasts.

Plant cells also contain thetonoplast, which control theexchange between the vacuole

and the cytoplasm.



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sorting and distribution systemwithin the cell.

Nucleus: the largest cell organelle;

surrounded by two membranes known as the

nuclear envelope.

Centrioles: a hollow cylinder about

0.4 m long, formed from a ring of

microtubules.

oThese microtubules are used to grow the spindle

fibers for nuclear division.



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Golgi Apparatus: a stack of flattened sacs. This

stack is constantly being formed at one end from

vesicles which bud off from the ER, and broken down atthe other end to form Golgi Vesicles.

o The apparatus collects, processes and sorts

molecules, read for transport in Golgi Vesicles

either to other parts of the cell or out of the cell.

oGolgi Vesicles are also used to make lysosomes.

Ribosomes: the components of cells that

make proteins from all amino acids.

Lysosomes: spherical sacs, surrounded by a single

membrane and having no internal structure.



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o They contain hydrolytic enzymes which must be

kept separate from the rest of the cell to prevent

damage.

o They are responsible for the breakdown of

unwanted structures.

Mitochondria: bean-shaped with inner membrane.

They break down sugar molecules into energy. Theirmain function is to carry out the later stages of aerobic

respiration, and as a result they make ATP, which is the

universal energy carrier in cells.

Endoplasmic Reticulum: there are two types ofEndoplasmic Reticulum:



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oRough ER: where the ER is covered by ribosomes;

transports the proteins throughout the cell.

oSmooth ER : lacks ribosomes and appears

smooth; synthesizes lipids and steroids,

metabolizes carbohydrates and steroids, and

regulates calcium concentration

Plasma membrane: separates the interior of allcells from the outside environment. The cell membrane

is selectively-permeable to ions and organic molecules

and controls the movement of substances in and out of

cells.

Cilia: long, thin extensions that can move in a

wave-like manner.



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o A few of these extensions are called flagella.

o If there are many of them and they are relatively

short then they are known as cilia.

Eye-piece graticule: a transparent

scale, usually with 100 divisions, placed withthe object on the microscope eyepiece so

that it can be seen at the same time as the

object and be measured.

Stage micrometer: used to calibrate

the eye-piece graticule.



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Magnification: the number of times larger an

image is compared with the real size of the object.

oMagnification =

Resolution: defined as the ability to

distinguish between two separate points.

Electromagnetic Spectrum: the

range of different wavelengths.

oThe longer the electromagnetic waves, the lower

their frequency.



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oWavelengths change with energy: the greater the

energy, the shorter the wavelength.

The limit of resolution is about one

half the wavelength of the radiation

used to view the specimen.

The electron microscope is used mainly

because electrons are negatively chargedparticles and free electrons behave like

electromagnetic wavelength.

They are a very suitable form of

radiation for microscopy because

o their wavelength is extremely short



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o they are negatively charged particles, which

means that they can be focused easily using

electromagnets.

There are two types of electron

microscopes:

oThe TEM (transmission electron microscope): the

beam of electrons is passed through the specimenbefore being viewed.

o The SEM (scanning electron microscope): the

electron beam is used to scan the surfaces of

strictures and only the reflected beam is observed.



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The one disadvantage of using a SEM is that it

cannot achieve the same resolution as a transmission

electron microscope.

Prokaryotes: organisms that lack nuclei.

o

Prokaryotes are referred to as bacteria.

Eukaryotes: organisms whose cells

possess nuclei.

o Eukaryotes are referred to as animals, plants,

fungi etc.



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Specialized cells show division of labor

by being grouped into tissues. The tissues are

then further grouped into organs and the

organs into systems.



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Tissue: a collection of cells, together

with any intercellular secretion produced by

them, that is specialized to perform one ormore particular functions.

oThe study of tissues is called histology.

Organ: part of the body which forms a structural

and functional unit and is composed of more than onetissue.

System: a collection or organs with a particular

function.



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