Cellular Level of OrganizationFTCE Biology 6-12

Day 1

Cell discovery timeline Hooke: 1660

– Cork, used term “cells” Van Leeuwenhoek: 1673’s

– Wee beasties, protists Schleiden: 1839

– Plants made of cells Schwann: 1839

– Animals made of cells

Cell theory Rudolf Virchow -1855 The cell theory

1. Cells are the units of structure & function in organisms.

2 . All cells come from pre-existing cells.

Cells are 1µm to 20µm small. Why is small better?– 1000 µm = 1mm– Ex. on pg. 156

Microscopes

Magnification: the ratio between the size of the image and the object

Resolution: the smallest degree of separation at which 2 objects appear distinct

Resolution (resolving power)

The ability to see clearly between two points.– Limited by the wavelength of the

source of illumination• Visible light is used for “light

microscopes”• Beam of electrons for EM

Two types of microscopes

Light microscope– Visible light to see image– Parfocal– Highest magnification with decent resolution =

about 1000x– Can observe living cells

Electron microscope– Electrons bounced off object– Highest magnification with decent resolution =

about 1,000,000x– Preparation is severe.

Two types of electron microscopes Transmission electron microscope

– (TEM)– 2-D image

Scanning electron microscope– (SEM)– 3-D image

Three Views of Red Blood Cells

Light Microscope

SEM

Scanning Probe Microscope

Parts of the microscope Eyepiece Arm Base Revolving nosepiece Stage

– Clips– diaphragm

Parts of the microscope cont. Nosepiece

–Objective lenses

• Low (book calls it scanning)

–4x magnification

• Medium (book calls it low)

–10x magnification

• High (book calls it same thing)

–40x magnification Overall mag. 10x (eyepiece) x lens

Parts of the microscope cont. Coarse focus knob

– Only when using

low power objective Fine focus knob

– For small

adjustments diaphragm Light switch

& cord

Two general types of cells Prokaryote

– No true nucleus– No membrane- bound organelles– Ex. Monera /bacteria

Eukaryotes – True nucleus– Membrane- bound organelles– Ex. Protist cells, fungi cells, plant cells,

animal cells

Prokaryote structure

Cell wall Plasma membrane Cytoplasm Nucleoid Plasmid (some) flagellum

Bacteria Shapes

Cocci/sphere Bacilli/rod Spirilla/spiral

Eurkaryotes

(Protists, Fungi, Plant, Animal)

• organelles

•plasma membrane

• cell wall of cellulose (plants)

• nucleus w/nuclear membrane

• nucleoli

• cytoplasm

amoeba

Amoeba

Paramecium

Onion skin

Elodea

Studying Cells

Cytology: Cyto-cell –ology study of Human body-2 types of cells

1. Sex cells: sperm (male)

oocyte (female)

2. Somatic cells: all other cells

Generalized Generalized

Animal Cell Plant Cell

Cell organelles

Cell Organelles

• Compartmentalize cell’s activities

• improve efficiency

• protect cell contents from harsh chemicals

• Enable cells to:

• secrete substances

• perform cellular respiration

• degrade debris

• reproduce

Cell Organelles

Cell membrane: lipid bilayer containing phospholipids, steroids, proteins and carbohydratesF-isolation: keeping proteins inside protection:

sensitivity: receptors that allow the cell to recognize and respond to

specific molecules.

Cell membrane (continued)

Structural support: to stabilize (skin)

Transport: control of entrance and exit of materials (ions, glucose, elimination of wastes)

• cytoplasm: entire contents of the cell, except the nucleus, bounded by the plasma membrane

• cytosol: gelatinlike portion of the cytoplasm that bathes the organelles of the cell

Organelles of Eukaryotic CellsOrganelles compartmentalize a cell’s

activities.1. Nucleus

– surrounded by a double membrane two phospholipid bilayers (nuclear

envelope), perforated with nuclear pores– contains DNA & nucleolus (stores RNA

nucleotides)– functions to separate DNA from rest of

cell

Nucleus Functions (Continued)

Controls metabolism Stores and processes genetic

information Controls protein synthesis

Nucleolus

Dense region in nucleoplasm of nucleus Site of rRNA synthesis and assembly of

ribosomal units

Nucleolus

Cytoskeleton Network of protein

filaments throughout the cytosol

Functions– cell support and

shape – Site of some

chemical reactions– cell & organelle

movement Continually

reorganized

Ribosomes Packages of Ribosomal RNA & protein Free ribosomes are loose in cytosol

– make proteins used inside the cell Membrane-attached ribosomes

– attached to endoplasmic reticulum or nuclear membrane

– make proteins needed for plasma membrane and/or for export

Inside mitochondria, synthesize mitochondrial proteins

Ribosome

Large + small subunits– made in the nucleolus

– assembled in the cytoplasm

2. Endoplasmic reticulum (ER)

–interconnected network of membranes extending from nucleus to plasma membrane

Rough ER - studded with ribosomes – site of protein production (most will be

exported out of the cell)Free ribosomes in the cytoplasm produce proteins that remain in cell.

Smooth ER - lacks ribosomes– site of lipid production– contains enzymes that detoxify drugs &

poisons

3. Golgi apparatus

–stacks of membrane-enclosed sacs

Golgi apparatus functions:– Forms membranes/vesicles (renews/modifies

cell membrane)– links simple carbohydrates together to form

starch– links simple carbohydrates to proteins

(glycoprotein) or lipids (glycolipid)– completes folding of proteins– temporarily stores secretions – Storage, alteration and packaging of

secretory products and lysosomal enzymes.

Organelle interaction in a mammary gland cell.

– #/cell varies with energy demands of that cell (bone cedll have few, muscle cell has thousands)

– contain DNA (some mitochondrial genes, rest in nuclear DNA)

– Contains some ribosomes for own protein synthesis– inherited only from female parent

– site of cellular respiration (production of ATP)– Takes in short carbon chains and oxygen to generate

carbon dioxide and ATP

4. Mitochondria– double-membrane

• outer is smooth• inner is highly folded

(cristae)

Plant cells also have...

• Cell wall: made of cellulose, provides rigidity and allows for turgor pressure

• Vacuole: contains water and digestive enzymes, stores nutrients and wastes

•Chloroplast: photosynthesis

Chloroplasts #/plant cell varies (few-hundreds)

contain DNA (some chloroplastic genes, rest in nuclear DNA) –found in plants &

protists–function

photosynthesis

6. Lysosomes (suicide sacs) apoptosis

programmed cell death– vesicles containing > 40 types of digestive enzymes

– function to recycle damaged organelles, break down cellular byproducts, destroy cell & kill invading microbes

Centrioles

Found near nucleus

–Involved in cell divison

Structurally similar to cilia and flagella

Cilia and FlagellaDifferences– cilia

• short and multiple– flagella

• longer and single

Movement of Cilia and Flagella Cilia

– Move material over cell surface

– Respiratory tree & oviduct

Flagella– single flagella wiggles in a

wavelike pattern– propels sperm forward

The Endosymbiont Theory

Lynn Margulis – eary 1960’s

Proposes that chloroplasts and mitochondria evolved from once free-living bacteria engulfed by larger prokaryotes, but not digested.

Based on fact that mitochondria & chloroplasts resemble certain bacteria (size, shape, membrane structure,have own DNA and ribosomes)

Multicellular Organization Each cell must do their own basic activities

(protein synthesis, cellular respiration, cell division, etc.)

Also show a division of labor or specialization and cooperation- contribute to the well being of other cells/tissues/organs etc.

Some form of intercellular communication– Either chemical (hormone) or electrical

(nervous)

Levels of Organization Subatomic Atom Molecule Macromolecule Organelle Cell Tissue Organs System Organism Population Community Ecosystem Biosphere

Levels of Structural Organization

Chemical Level– Subatomic, atomic and molecular level

Cellular level– smallest living unit

– Tissue level– group of cells that work together on one task

Organ level– groups of 2 or more tissue types into a

recognizable structure with a specific function. Organ system

– collection of related organs with a common function

– sometimes an organ is part of more than one system

Organism level– one living individual

Levels of Structural Organization

Population– Group of same specie in a given area

Community– All specie in a given area

Ecosystem– Biotic and abiotic in a given area

Biosphere– All ecosystems combined

Levels of Structural Organization