Cell Structure and Function. Why are cells small?

Cell Structure and Function

Why are cells small?

Viruses

Virus Morphologies

viral capsids

Cellular OrganismsProkaryotes and Eukaryotes

Life on Earth

CellAll cellular organisms have a

Protoplast:the cytoplasm and its

surrounding plasma membrane

Some organisms have a

Cell Wall(polysaccharide)

plantsfungi

some protistsmost bacteria

Bacteria often have a

CapsuleWhich is a gooey outside covering for protection

(polysaccharide)

ProkaryotesBacteria and Archaea

The cytoplasm is an active environment

protein

ribosome

tRNA

Few bacteria have internal membrane systems.This bacterial species does.

Three major morphologies

rods

cocci

spirochaetes

Prokaryotes are usually much smaller than Eukaryotes

Life on Earth

Eukaryotic Cell

Paramecium

The Nucleus

Eukaryotes

Nucleus

Activities of the Nucleus

• Replication of DNA

• Gene Expression: Synthesis of RNA

• Ribosome subunit assembly (in nucleolus, where rRNA genes are expressed)

Nucleus

Activities of the Nucleus

• Replication of DNA

• Gene Expression: Synthesis of RNA

• Ribosome subunit assembly (in nucleolus, where rRNA genes are expressed)

Nucleolus and rRNA genes

Invagination Hypothesis

1. The original eukaryotic cells probably had no cell wall

2. RNA splicing in eukaryotic genes

Exon 1 Exon 2 Exon 3

Intron 1 Intron 2 Intron 3 Intron 4

Intron 1

Intron 2

Intron 3

Intron 4

Bacteria transcribe and translate simultaneously …no time for RNA splicing

DNA Packaging - Chromosomes

HumanKaryotype

Chromosome Structure

Chromosomes

Centrioles in Centrosome also build the Spindles

Flagella and cilia

Structure of Flagella & Cilia

How Flagella and cilia move

Cytoskeleton

Ribosomes: Sites of protein synthesis

Ribosomes: Sites of protein

synthesis

Membrane Systems:synthesis, degradation and transport

• Nucleus

• RER

• SER

• Golgi Apparatus

• Lysosomes

Rough Endoplasmic Reticulum

nuclear envelope

nucleolus

roughendoplasmic reticulum

protein synthesis

ribosome

Smooth ER lipid synthesis Rough ER protein synthesis

Nucleus, RER, SER membranes are continuous

ribosomenucleus

Golgi Apparatussynthesis of molecules for export and degradation

cis face“receiving”

trans face“shipping”

new vesicle forming

transport vesicles carrying cargo molecules

transportvesicle

DEGRADATION

EXPORT

Digestion: Eating and Recycling

Energy Transformation

sugarATP

sunlightsugar

“savings bond”“cash”

Mitochondria and Chloroplast Comparison: Similar to Bacteria

Mitochondrion

Chloroplasts

Endosymbiont Hypothesis

Endosymbiont Hypothesis

Invagination Hypothesis

Vacuoles

Vacuole

Plant Vacuoles

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plasmolysis

Practice

Practice