Cell Structure and Function 1. The Cell Theory A. All organisms composed of one or more cells B. Cell is smallest living organizational unit C. Cells arise only from division of other cells

Attributes of cells A. Plasma membrane B. DNA C. Cytoplasm D. Obtain energy and nutrients from their environment

Cell Size 1–100µ Cell Size A. Limitations of molecular diffusion 1. Faster passage through small cell 2. More efficient communication B. Limitations of surface-to-volume ratio 1. With increase in size, greater increase in volume than surface area a. Interaction with outside occurs only at surface b. Insufficient exchange of materials at plasma membrane for survival

diameter of DNA double helix tallest trees adult human chicken egg frog embryo most eukaryotic cells mitochondrion Figure: 04-01 Title: Relative sizes. Caption: Dimensions commonly encountered in biology range from about 100 meters (the height of the tallest redwoods) through a few micrometers (the diameter of most cells) to a few nanometers (the diameter of many large molecules). most bacteria virus proteins diameter of DNA double helix atoms

Cell types Prokaryotic—no nucleus, circular DNA, ribosomes, peptiglycon-prokayotic cell wall a. Carbohydrate matrix cross linked with peptide units Eukaryotic—larger, nucleus, linear chromosomes, membraned organelles, Compartmentalization Include true bacteria On earth 3.8 million years Found nearly everywhere Spores in each breath; intestines Naturally in soil, air, hot springs

nucleoid (DNA) ribosomes food granule cytoplasm cell wall prokaryotic flagellum Figure: 04-10 Title: A generalized prokaryotic cell. Caption: plasma membrane cytoplasm cell wall

Eukaryotic Cells Have numerous internal structures Various types & forms Plants, animals, fungi, protists Multicellular organisms Nucleus is control center of the cell 1. Membrane bound (nuclear envelope) 2. Contains nucleoli; synthesizes ribosomal RNA 3. DNA in chromosomes (DNA and proteins)

1. Plant cells a. Square-geometric shaped b. Cell wall- cellulose c. Chloroplast d. No centrioles e. Large vacuoles

(part of cytoskeleton) microtubules (part of cytoskeleton) mitochondrion chloroplast Golgi complex central vacuole smooth endoplasmic reticulum vesicle cell wall rough endoplasmic reticulum plasma membrane Figure: 04-03 Title: A generalized plant cell. Caption: nucleolus nuclear pore nucleus chromatin nuclear envelope intermediate filaments ribosomes free ribosome

Animal Cells a. Irregular shaped b. Just Cell membrane c. Small vacuoles d. Centrioles

nuclear pore chromatin (DNA) nucleus nucleolus nuclear envelope flagellum intermediate filaments cytoplasm plasma membrane rough endoplasmic reticulum ribosome lysosome microtubules Figure: 04-02 Title: A generalized animal cell. Caption: smooth endoplasmic reticulum Golgi complex free ribosome vesicle mitochondrion vesicle

nuclear envelope nucleolus nuclear pores chromatin Figure: 04-04a Title: The nucleus. Caption: (a) The nucleus is bounded by a nuclear envelope. Inside are chromatin (DNA and associated proteins) and a nucleolus. chromatin

nucleus nuclear pores Figure: 04-04b Title: The nucleus. Caption: (b) An electron micrograph of a yeast cell that was frozen and broken open to reveal its internal structures. The large nucleus, with nuclear pores penetrating its nuclear envelope, is clearly visible.

chromatin chromosome Figure: 04-05 Title: Chromosomes. Caption: Chromosomes, seen here in a light micrograph of a dividing cell (on the right) in an onion root tip, are the same material (DNA and proteins) as the chromatin seen in nondividing cells adjacent to it, but in a more compact state. chromosome

Figure: 04-06 Title: Ribosomes. Caption: 0.05 micrometers

Eukaryotic cell structure Organelles Endoplasmic reticulum consists of folded membranes attached to the nucleus Rough ER is site of protein synthesis and protein secretion. Proteins made here are processed and shipped out of the cell

Eukaryotic Cell Structure Ribosomes assemble amino acid into polypeptide chains a. Associated with the ER b. Composed of RNA and proteins Proteins for inside the cell

rough endoplasmic reticulum ribosomes Figure: 04-07R-1 Title: Rough endoplasmic reticulum. Caption: rough endoplasmic reticulum 0.5 micrometers

smooth endoplasmic reticulum vesicles Figure: 04-07R-2 Title: Smooth endoplasmic reticulum. Caption: smooth endoplasmic reticulum 0.5 micrometers

Eukaryotic Cell Structure Golgi apparatus are membranous sacs associated with ER Processing and transport of proteins, lipids exported from the cell Synthesis and transport of polysaccharides Lysosomes are Golgi-derived vesicles containing digestive enzymes

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vesicles from ER vesicles leaving Golgi complex Golgi complex Figure: 04-08 Title: The Golgi complex. Caption: The Golgi complex is a stack of flat membranous sacs. Vesicles transport material from the ER to the Golgi (and vice versa) and from the Golgi to plasma membrane, lysosomes, and vesicles. Departing vesicles bud off from the Golgi on one face; arriving vesicles join it on the opposite face.

Energy sources for cell activities Mitochondria provide energy for cellular functions (respiration) a. Matrix/cristae b. Have their own DNA and ribosomes; self- replicate C. Bounded by double membrane-numerous a. Outer membrane is smooth b. Inner membrane is folded into contiguous layers called cristae 1. Cristae are stuffed with 100,000 enzymes 2. Site of cellular respiration-Oxidation 3. Divides into inner matrix and outer compartment 4. Associated with proteins of oxidative metabolism

5 micrometers Figure: 04-E4-2d Title: An SEM photo. Caption: (d) An SEM photo at much higher magnification, showing mitochondria, many of which are sliced open. 5 micrometers

Energy sources for cell activities Chloroplasts—function in photosynthesis 1) Green—contain chlorophyll pigment 2) Stroma/grana (thylakoid stacks) 3) Have their own DNA and ribosomes; self-replicate 4) Up to 100 per cell 5) Become leucoplasts when deprived of light a. Specialized amyloplasts store starch b. Plastids are derived from proplastids

Cytoskeleton Cytoskeleton Surface structures Internal infrastructure a. Actin filaments-microfiliments a. Muscle movement b. Pinches cell when it divides during cytokinesis b. Microtubules 1. Hollow tubes of 13 protein protofilaments-made of tubulin 2. Function a. Help move materials within the cell itself b. Skeletal System c. Aides in cell Division-spindle d. Cilia, Flagella, sperm tails c. Intermediate filaments Surface structures extensions of the plasma membrane aid in movement of simple organisms

actin subunits subunit tubulin subunit Figure: 04-2 Title: Cytoskeleton components. Caption: tubulin subunit

Prokaryotes & Eukaryotes Similarities & differences Both surrounded by plasma membrane, but very different Prokaryotes – Archaebacteria and Eubacteria Eukaryotes – everything else

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Evolution of Eukaryotic cell Endosymbiotic Hypothesis Similarities between bacteria, mitochondria and chloroplasts Self-reproducing by binary fission Size of organism and genome Single circular naked DNA Proportion of (G & C) to (A & T) Same sized ribosome Protein synthesis inhibited by antibiotics Enzymes for synthesis of DNA, RNA and protein Electron transport system

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Plant & Animal Cells Similarities Both constructed from eukaryotic cells ________________________________________________________________________________ Both contain similar organelles __________________________________________________________________________________ Both surrounded by cell membrane _________________________________________________________________________________

Plant & Animal Cells Differences Animals have Plants have Cell wall – provides strength & rigidity Have chloroplasts, photosynthetic Animals have Other organelle not found in plants (lysosomes formed from Golgi) Centrioles, important in cell division

Brief Look at Viruses Viruses are acellular Not considered to be living Cause serious diseases in most organisms