As Biology Cell Project Part 1

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AS BIOLOGYThe ultrastructure of the cell

LEARNING OBJECTIVES

By the end of this section you should be able to:-

Recognise the following organelles from a diagram of theeukaryotic animal and plant cell (rough and smooth endoplasmicreticulum, Golgi apparatus,mitochondria, ribosomes, lysosomes,chloroplasts, plasma (cell surface) membrane, nuclear envelope, centrioles,

nucleus, nucleolus and cilia).

Outline the functions of the following structures:-rough andsmooth endoplasmic reticulum, Golgi apparatus, mitochondria, ribosomes,

lysosomes, chloroplasts, plasma (cell surface) membrane, nuclearenvelope, centrioles, nucleus, nucleolus and cilia.

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The Eukaryotic Cell

The BeginningsRobert Hooke was the first person to observe cells in 1665.He looked at thin slices of cork under a very simple microscope.The cork appeared as little boxes which he called cells.In 1883 MathiasSchleiden and Theodor Schwann proposed that all

plants and animals were composed of cells which were the basicbuilding blocks of life.In 1855 Rudolf Virchow stated that new cells arise from thedivision of pre-existing cells and that chemical reactions needed forlife occurred inside the cell.All this work led to the formation of the cell theory(click to

complete exercise on cell theory)

For more information click on link belowhttp://fig.cox.miami.edu/~cmallery/150/unity/cell.text.htm

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Eukaryotic Animal Cell

Eukaryotic means true nucleus Eukaryotic cells have a nucleus which contains the

DNA. Eukaryotic animal cells are surrounded by a cell

membrane. Inside is the jelly like substance called cytoplasm. Contained in the cytoplasm is the nucleus and other

organelles(copy the glossary file into your area and continue to add words and meanings) The other cell organelles include the endoplasmic

reticulum,(rough & smooth) mitochondria, Golgiapparatus, ribosomes, lysosomes, centrioles, cilia,nucleolus.

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Endoplasmic Reticulum

STRUCTURE

Complex system of sheet likedouble membranes continuouswith the nuclear membrane

Fluid filled spaces/sacs

between the membranescalled CISTERNAEwhichallow materials to betransported through cell

Two types of ER

smooth has no ribosomesattached (RER)

rough has ribosomesattached (SER)

FUNCTION

Forms an extensive transportsystem

Site of protein synthesis(Rough ER)

Site of lipid, steroid andcarbohydrate synthesis(smooth ER)

Stores and transports thesematerials

SEE DIAGRAM

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MitochondriaSTRUCTURE

Relatively large organelle Rod/sausage shaped 1um

5um Have a double membrane

The outer controls the entry &exit of materials

Inner has many folds calledcristae Surface of each crista is covered

with stalked particles where ATPis made

Mitochondria are filled with a jellylike matrix

The matrix contains proteins,lipids, ribosomes and loops ofDNA

Mitochondria can replicatethemselves when the cell divides

FUNCTION

Site of aerobic respiration (Krebscycle & oxidative phosphorylation)

Responsible for the production ofenergy rich ATP molecules

The numbers of mitochondriareflect the metabolic activity of thecell so large numbers are foundin muscle and liver cells

SEE DIAGRAM

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Golgi apparatus

STRUCTURE

Formed from small pieces ofrough ER which form smallvesicles which join to make aGolgi body

Chemicals made in the ERcollect in the Golgi body wherethey are modified

Small vesicles can then bepinched off the Golgi bodycarrying new chemicals awaywhich are secreted when the

vesicle reaches the cellmembrane

Some of the vesicles becomelysosomes

FUNCTION

Assembling glycoproteins(such as mucin) by combiningcarbohydrate and protein

Transporting and storing lipids

Formation of lysosomes Producing digestive enzymes Secretes carbohydrates which

are used in the formation ofplant cell walls and in insectcuticles

SEE DIAGRAM

What have you learnt?

Click here to walk the plank

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Ribosomes

STRUCTURE

Small dense structures foundin huge numbers.

Can be attached to the roughER of floating in the cytoplasm.

Are about 20 25 nm indiameter in eukaryotic cellsand slightly smaller inprokaryotic cells

(80s type prokaryotic)

(70s type eukaryotic) Made up from two sub units

FUNCTION

Synthesize proteins

Synthesize enzymes

SEE DIAGRAM

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Lysosomes

STRUCTURE

Small vacuoles formed whensmall pieces of Golgi body arepinched off

Contain hydrolytic enzymes

which digest materials in thecell

SEE DIAGRAM

FUNCTION

Release enzymes whichdestroy worn out organelles

Digest material taken into thecell (eg white blood cells which

have engulfed a bacterium)phagocytosis

Release enzymes to theoutside of the cell which digestmaterial around the cell

exocytosis Completely break down cellsafter they have died autolysis

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Plasma (cell surface) membrane

STRUCTURE

This is the boundary betweenthe cell cytoplasm & theenvironment

Is partially permeable

Made up 45% protein & 45%phospholipids with theremaining 10% cholesterol,glycoprotein & glyolipids

FUNCTION

Controls movement ofsubstances in & out of the cell

Forms a recognition site sothat the bodys immune system

can recognize its own cells Acts as a receptor site for the

attachment of specifichormones andneurotransmitters.

SEE DIAGRAM

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Nucleus, Nucleolus &Nuclear envelope

STRUCTURE

Largest organelle in the cell (10umdiameter)

Surrounded by a nuclear membrane/ envelope

Double membrane outer iscontinuous with the ER

Nuclear pores in the membraneallow the passage of largemolecules in & out (egmessengerRNA)

Material inside the nucleus is callednucleoplasm this containschromatin which makes up the DNA

of the cell in non-dividing cells it isspread out and during cell division itcondenses to form thechromosomes

A spherical structure called thenucleolus is found in the nucleusthis makes ribosomal RNA and

assembles the ribosomes.

FUNCTION

Acts as the control centre of thecell through the production ofmRNA and protein synthesis

Retains the genetic material in the

cell in the form of DNA /chromosomes

Manufactures ribosomal RNA(rRNA) & ribosomes

Starts the process of cell division

SEE DIAGRAM

What have you learnt? Click here to complete the

crossword

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Cilia

STRUCTURE

3-10 um in length, 0.2umin diameter

Made of rings of 9 pairs

of microtubules Have basal bodyembedded in cytoplasm

Rest extends from basalbody

Only a few types of cellpossess cilia On cells which have cilia

there are large numbers

FUNCTION

To move an entireorganism (eg inparamecium it propels itthrough the water)

To move material withinan organism ( eg cilia inthe lining of therespiratory tract)

SEE DIAGRAM

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CENTRIOLES(not found in plant cells)

Two short bundles of hollow cylinders (microtubules)positioned at right angles to each other

Found just outside the nucleus in a clear area ofcytoplasm called the centrosome

Wall of each centriole is made of 9 triplets of tubesarranged at an angle

During cell division they migrate to opposite poles toproduce the spindle which helps to move thechromosomes during cell division

SEE DIAGRAM

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Chloroplasts

Found inside photosynthetic tissues of plants (abundant in palisade

mesophyll cells of leaves) Flat discs 2-10 um in diameter & 1um thick Have a double membrane called the chloroplast envelope Inner membrane folded into a series of lamellae Membrane controls the entry & exit of substances Inside the membrane is a fluid stroma which contains the enzymes

involved in photostnthesis Small amounts of DNA and oil are found in the stroma In stroma is a network of flattened sacs called thylakoids Grana (granum = sing) are formed when many thylakoids are stacked

together (like a pile of coins) (thylakoids also called lamella) Chlorophyll molecules are attached to the thylakoids

Large starch grains are also present which act as a tempory store ofcharbohydrate made in photosynthesis SEE DIAGRAM Click here to label the eukaryotic animal cell

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Click here to play cell organelles

catch phrase