cell structures and its function

8/22/2019 Cell Structures and Its Function

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The Cell Structure


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The Dawning of Cytology

1665

Robert Hooke- reported that thin slices of corkcontained minute partitions separating cavitiescell.

1808

Mirbel concluded that plants are formed ofmembranous cellular tissue

1809 Lamark stated that any living being must have its part

of cellular tissue or formed by such tissue


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History of cytology continued

1833

Robert Brown described the nucleus asa central feature in plant cells

1838

Schleidencells were the unit ofstructure

1839

Schwann applied Schleidens thesis toanimals


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Cytology

1840

Purkinje named cell componentsprotoplasm


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The Cell Theory

All living things (plants and animals) are made

up of cells and cell products (Schleiden and

Schwann)

The cell is the basic unit of structure, function,

and organization of living things.

All cells come from pre-existing living cells (R.

Virchow)


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Types of Cells

Image source: libarary.thinkquest.org


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Types of Cells

Charactersitic Prokaryotes Eukaryotes

Cell Size Mostly small (1-10

microns)

Mostly large (10-100

microns)

Genetic System DNA w/o histone protein;

simple Circular loop-

plasmid in nucleoid,

nucleoid is not membrane

bound

DNA complexed with

histone and nonhistone

proteins in complex

chromosomes within the

nucleus with membranous

envelope

Cell Division Direct by binary fission or

budding; no mitosis

Some form of mitosis;

centrioles in many; mitoticspindle present

Sexual Sytem Absent in most; highly

modified if present

Present in most; male-

female partner; gametes

that fuse to form zygote


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Types of Cell

Characteristic Prokaryotes Eukaryotes

Nutrition Absorption by most;

photosynthesis by some

Absorption; ingestion,

photosynthesis by some

Energy Metabolism No mitochondria; oxidative

enzymes bound to cell

membrane, not packagedseparately; great variation

in metabolic pattern

Mitochondria present;

oxidative enzymes

packaged therein; moreunified pattern of oxidative

metabolism

Intracellular Movement None Cytoplasmic Streaming,

phagocytosis, pinocytosis

Flagella/ Cilia Ifpresent, not with 9+2microtubular pattern Axoneme structure

Cell Wall Contains disaccharide

chains cross linked with

peptides

If present, not with

disaccharide polymers

linked with peptides


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Cellular Structures

Image source: www.ebi.ac.uk


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The Lipid Bilayer

Image source: www.uic.edu


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The Lipid

Bilayer

Image source:

www.uic.edu


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Membrane Proteins

Image source: rci.rutgers.edu


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Image Source: Taiz and Zaiger


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The Nucleus

Image Source: micro.magnet.fsu.edu


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Endoplasmic reticulum

Image Source: Hickman, et al. 2004


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Golgi Complex

Image Source: Hickman, et al. 2004Image Source: vetmed.vt. edu


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Mitochondria



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Cytoskeleton



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Surface Specialization of the Cell

1.) Cilia and

Flagella

Axoneme

Image Source:worms.zoology.wisc.edu


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2. Junctional Complexes

Tight jxn

Gap Jxn

Desmosome

3. Microvilli



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Membrane Functions

1.) Diffusion and Osmosis



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2.) Mediated Transport



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Types of Mediated Transport

1.) Facilitated

Diffusion

2.) Active Transport

-Primary

-Secondary

Image Source: Guyton and Hall 2006


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Facilitated Diffusion



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Active Transport



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3.) Endocytosis

Phagocytosis

-cell eating-common among

protozoa and lower

metazoa



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Potocytosis

-caveolae

Receptor

Mediated

Endocytosis



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The Chromosome Structure

Chromatids

Kinetochore

Microtubule



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The Cell Cycle

Image source: scientopia.org


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Cell Cycle

ControlMPF- Mitosis

Promoting Factor

-made up

of two proteins

(1) Cyclin-

oscillating

component

(2) Cdk-a kinase;

constant in number


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Mitosis

Image source: Dedunn.edublogs.org


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Importance of Mitosis

-preservation of 2n state

-cytokinesis and mitosis result in 2 daughter cells

-perpetuation of genetic material identical to that

of the parent cell

-stability of cells and inheritance of traits


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Image source: geneticssuite.net


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Meiosis

Image source: toksource.org


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Image source: britannica.com


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Significance of Meiosis

(1) Reduces the 2n so that each daughter cells

has one complete n chromosome set

(2) Randomness of the process of chromosomal

separation causes a very large no. of

possible chromosomal combination

(3) Crossing overmore allelic combination


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What are telomerases?

cell structures and its function

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