Biology Chapter 6 - Support Center - FacultyWeb Support …facultyweb.wcjc.edu/users/kevind/documents/BIOL_140… · · 2018-01-29Chapter 6 A Tour of the Cell Biology – Kevin

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Biology – Kevin Dees

Chapter 6A Tour of the Cell


• The cell is the basic unit of life• Although cells differ substantially from one

another, they all share certain characteristics that reflect a common ancestry and remind us of the unifying theme of evolution

• Three main parts of a cell– Plasma membrane– Cytoplasm– Genetic control

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History of the cell

• First ‘microscopes’ – 1590 - technology• The term ‘cell’ was first coined by Robert

Hooke in 1665.• Little knowledge was gained about cell

structure –function until the 1950’s– WHY???– Technology


Microscopes• Essential tool for studying the cell

– Light microscopes –• Ratio of image size to actual size –

magnification• Measure of clarity – resolution• Many of the essential components of cells

were too small for adequate resolution by a light microscope

– Electron microscopes – much higher magnification and resolution • Electron microscopes made the detailed

study of cell ultrastructure possible

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Comparison of Light , Transmission electron and Scanning Electron microscopy

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Recall, that there are two basic categories of cells:

• Prokaryotic cells – organisms in the Domain Archaea and Bacteria are prokaryotic in structure

• Eukaryotic cells – plants, animals, fungi, etc..


Prokaryotic cells

• Very simple – contain:– Plasma membrane– Cytoplasm– Genetic control

• No nucleus –prokaryotic chromosome is not enclosed in a membrane!!!!!

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Eukaryotic cells

• True nucleus – genetic material is surrounded by membrane.

• Typically larger than prokaryotic cells but still small

• Why are cells small?• Large living things typically do not have

larger cells? Why??


Plasma membrane• Forms a selective barrier to allow the controlled passage

of materials in and out of the cell• Phospholipid bilayer with proteins• Forms the surface area of a cell

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Surface area regulates cell size• Materials must pass in-out of cell.• Must pass through plasma

membrane


Comparison of typical animal and plant cells

• Recall the three components that all share have in common:– Plasma membrane– Cytoplasm– Genetic control

• We are going to survey generalized animal and plant cells– Look for similarities and differences between

the two

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General Animal cell

• Plasma membrane

• Microvilli

• Flagellum

• Cytoplasm

• Mitochondrion

• Cytoskeleton

• Centrosome – pair of centrioles


General Animal cell

• Endoplasmic reticulum– Rough ER– Smooth ER

• Ribosomes

• Golgi complex

• Lysosome

• Peroxisome

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General Animal cell

• Nucleus– Nuclear

envelope– Nuclear pores– Nucleolus– chromatin


General Plant cell

• Cell wall– plasmodesmata

• Central vacuole– Tonoplast-turgor

pressure• Chloroplast

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A closer look at the nucleus

• Nuclear envelope• Nuclear pores

– Nuclear pore complex– Transport of materials

• Nucleolus– Ribosome production

• Genetic material– Chromatin– Chromosomes

• During cell division– Humans – 23 pair of

chromosomes in somatic cells; 23 single in gametes

• Why??????


• Made of ribosomal RNA and proteins– Large and small subunits form ‘sandwich’

• Carry out protein synthesis• Not surrounded by a membrane• Free ribosomes – floating in the cytoplasm

– Synthesize proteins that have a function in the cytoplasm• Bound ribosomes – attached to ER or nuclear envelope

– Synthesize proteins for insertion into cell membranes, lysosomes, or export from cell

A closer look at ribosomes

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• Endomembrane system includes the SER, RER, the nuclear envelope, the Golgi apparatus, various vesicles and vacuoles and the plasma membrane

• SER– Synthesis of lipids,

steroids, phospholipids– Detoxification

• RER– Important in protein

synthesis– produces more

‘membrane’ for the cell• Transport vesicles

A closer look at the endomembrane system


• The cis face is located near the ER– Transport vesicles from the ER move materials to the Golgi

• The trans face is located away from the ER – Gives rise to vesicles which move away from the Golgi

A closer look at the Golgi apparatus

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• Lysosomes – found in animal cells– Membranous sacs of

hydrolytic enzymes for intracellular digestion

• Phagocytosis –creation of food vacuole and subsequent digestion

• Autophagy – recycles cellular components


• Vacuoles - storage sacs– Food vacuoles– Central vacuole

found only in plant cells

• Tonoplastmembrane

• Turgor pressure –water

– Storage of electrolytes

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• Mitochondria– Cristae– Mitochondrial matrix– Free ribosomes and mitochondrial DNA– Site of aerobic cellular respiration and majority of

ATP production


• Chloroplasts – Found in plant cells only

• Site of photosynthesis within the cell• Chlorophyll and other pigments• Chloroplast DNA and ribosomes• Thylakoid membranes• Grana – stacks of thylakoids• Stroma – fluid filled area outside the thylakoids

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Elements associated with the cytoskeleton - Functions for support, motility and

regulation• Centrosome –

animals cells– Pair of centrioles– Creation of the

mitotic spindle used during cellular division


• Cilia

• Flagella

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Cell wall of plants

• Composed of primarily cellulose

• Structure for plant cell• Plasmodesmata

– Connections between plant cells

• Middle lamella – joins adjacent plant cells


Cellular junctions• Plant cells

– Plasmodesmata• Animal cells

– Tight junctions• Continuous seal

– Gap junctions• Communication

between cells– Desmosomes

• ‘rivets’

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All activities of cells must be coordinated

• The ability of the macrophage to recognize the harmful bacteria, locate them, capture them, and engulf them to be destroyed takes a coordinated effort

Documents

Biology Chapter 6 - Support Center - FacultyWeb Support …facultyweb.wcjc.edu/users/kevind/documents/BIOL_140… · · 2018-01-29Chapter 6 A Tour of the Cell Biology – Kevin