honors biology: chapter 4

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures forBiology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon

Lectures by Chris Romero

Honors Biology: Chapter 4

A Tour of the Cell


The Art of Looking at Cells

• Artists have long found inspiration in the visual richness of the living world

• Conversely, scientists use art to illustrate their findings

– Micrographs show structures as scientists see them

– Drawings can emphasize details

Biology is a visual science

Santiago Ramon y Cajal (1852-1934) anatomist

- Nerve cells in the retina

Wasily Kandinsky

(1866-1944)

– is it based on a cell?


Contributions to The Cell Theory

Zaccharias Jansen – first compound scope

Robert Hooke 1660s – term for “cells”

• Saw cork cell walls

• Tiny compartments

• Called them “cells”


Anton von Leeuwenhoek

Anton von Leeuwenhoek 1660s

first high-mag microscope

living cells, bacteria

Pond water, blood, saliva


Other cell discoveriesRobert Brown – 1830s

• nucleus in all cells

Matthias Schleiden 1830s

• all plants made of cells

Theodore Schwann 1830s

• all animals made of cells

Rudolf Virchow 1850s

• new cells come from cell division


The Cell Theory

1. All organisms are made of one or more cells

2. The cell is the basic unit of life. Cells that form part of a larger organism still do their own life processes.

3. All cells come from pre-existing cells


4.2 Why are all cells small?Cells vary in size and shape

Must be big enough to contain raw materials and molecules needed by cell

Must be small enough to have fast exchange with environment

Surface area must be large compared to volume 5


size increases 2X area increases 4X volume increases 8X

Cells have a large Surface-to-Volume Ratio

6


Most cells are microscopic


Two basic kinds of cells Prokaryotic Eukaryoticsmall and simple larger and more complexno nucleus nucleusbacteria all other organisms

Both have: DNA & complex chemicals cell membrane cytoplasm ribosomes


Two kinds of cells – small and large

Bacteria (purple) in animal cell (pink)

LE 4-3a

Nucleoidregion

Prokaryotic cell

Nucleus

Col

oriz

ed T

EM 1

5,00

0

Eukaryotic cellOrganelles

Two kinds of cellsSimple and complex


Prokaryotic cells “before nucleus”

• Very small (1-10mm)• No nucleus or other

membrane-bound organelles

• DNA in nucleoid region in cytoplasm


ALL prokaryotes have1. Cell (plasma) membrane

• Encloses cytoplasm, selectively permeable

• Controls what enters and leaves cell

2. Nucleoid

• Region containing DNA in a chromosome

3. Cell wall – various kinds of polysaccharides

• Outside cell membrane

• Cell shape and protection


SOME prokaryotes have4. Capsule – protective layer

– Slimy or sticky coating, outside cell wall

5. Pili – extensions of cytoplasm and membrane

• to attach to other cells, pass signals

6. Prokaryotic flagella – for movement

7. Plasmids – small rings of DNA

• For sexual reproduction

• have their own genes


Some prokaryotic (bacterial) cells

Common shapes of bacteria


Eukaryotes “true nucleus”

4.4 Eukaryotic cells are partitioned into compartments• Larger than prokaryotic (10-100 mm)

• Many organelles – tiny “organs”, specific functions

• Most organelles are enclosed by membrane

– Compartments - different metabolic processes

– Keeps chemistry inside organelle separate from rest of cell

– Enzymes often are parts of the membranes, greatly increase surface for reactions


Eukaryotic Cells

The cell is like a city – every part has a job to do. Together these parts keep the cell alive.


How do plant and animal cells differ? Both have most of the same organelles except:

Plant cells also have:1. rigid cell wall, contains cellulose – - protects photosynthetic tissue inside2. chloroplasts – do photosynthesis

3. large central vacuole – stores water and minerals for photosynthesis, wastes

Animal cells have: 1. centrioles – aid in cell division

2. lysosomes – contain hydrolytic enzymes

3. some have flagella or cilia

LE 4-4a

Roughendoplasmicreticulum

Smoothendoplasmicreticulum

Nucleus

Flagellum

Lycosome

Centriole

Not in mostplant cells

Peroxisome

MicrotubuleIntermediatefilamentMicrofilament

Cytoskeleton

Golgiapparatus

Ribosomes

Plasma membrane

Mitochondrion

LE 4-4b

Not inanimalcells

Golgiapparatus

Nucleus

CentralvacuoleChloroplastCell wall

Mitochondrion

Peroxisome

Plasma membrane

Rough endoplasmicreticulum

Smooth endoplasmicreticulum

Ribosomes

MicrotubuleIntermediatefilamentMicrofilament

Cytoskeleton


Cytoplasm

Cytoplasm: Watery solution outside nucleus

Contains organelles, each has a function

Many dissolved substances for metabolism

Site for chemical reactions

Cytoplasm and nucleus work together


4.5 Nucleus: the cell's genetic control center

• Has MOST of a cell’s DNA

• DNA in chromosomes• Chromatin - loose,

thread-like form of chromosome in

non-dividing cell • Controls cell by

directing synthesis of proteins

Also contains nucleolus – makes ribosomes


Structures in a nucleus

chromatin

Nuclear pores

Nuclear membrane

nucleolus

Nucleolus – makes ribosomes


Nuclear EnvelopeDouble-layered membrane surrounding nucleus

Many pores for molecules to pass through

Selectively permeable – controls what moves in and out of nucleus


Nuclear poresControl flow of materials in and out of nucleus


4.6 Endomembrane SystemA collection of membranous organelles

- divide the cell into compartments

• - work together to synthesize, store, and export molecules

Example: Endoplasmic reticulum (ER)

– Continuous network of flattened sacs and tubes throughout cell

LE 4-5

Chromatin

Nucleolus

Pore

Nucleus

Two membranesof nuclear envelope

Roughendoplasmicreticulum

Ribosomes


4.7 Smooth Endoplasmic ReticulumNo ribosomes on membrane

• Smooth ER has a variety of functions

– Synthesizes lipids

– In liver cells, processes materials such as toxins and drugs

– In muscle cells, stores and releases calcium ions needed for muscle contraction


4.8 Rough Endoplasmic ReticulumRough ER makes membrane and proteins

• Ribosomes on membrane make proteins

• RER modifies proteins made by ribosomes and transports to other parts of cell

• Some sent to Golgi body for further processing


Organelles that Build ProteinsRibosomesMake proteins, use instructions in DNA

Made of RNA and protein

Made in nucleolus, move to cytoplasm and rough ER

LE 4-7

Smooth ER

Rough ER

Nuclearenvelope

Ribosomes

Smooth ER Rough ER

TEM

45,

000

LE 4-8

Transport vesiclebuds off

Ribosome

Polypeptide

Glycoprotein

Sugarchain

Rough ER

Secretary(glyco-) proteininside trans-port vesicle


4.9 Golgi BodyThe Golgi apparatus finishes, sorts, and ships cell products

• Stacks of flattened membrane sacs

• Receives and modifies proteins from ER

• Sorts, packages into tiny vesicles

• Final products may be used inside cell – ex. Lysosomes

• Some exported – ex. Hormones, neurotransmitters

LE 4-9

Golgiapparatus

“Receiving” side ofGolgi apparatus

Transportvesiclefrom ER

New vesicleforming

“Shipping”side of Golgiapparatus Transport

vesicle fromthe Golgi

Golgi apparatus

TEM

130

,000


4.10 Lysosomes –digestive compartmentsLysosomes are sacs of enzymes that form from the Golgi apparatus

– Break down wastes and worn-out cell parts

– Recycle molecules the cell can use

– In protozoans, bind to food vacuole to digest food

– In white blood cells, destroy bacteria that have been ingested

– In development, removes tissues no longer needed

– Cell death, when cell is damaged beyond repair

Animation: Lysosome Formation

LE 4-10a

Plasmamembrane

Rough ER

Lysosomes

Transport vesicle(containing inactivehydrolytic enzymes)

Golgiapparatus

Engulfmentof particle

“Food”

Foodvacuole

Digestion

Lysosomeengulfingdamagedorganelle

LE 4-10b

Lysosome

Nucleus

TEM

8,5

00 Lysosomes are stained

in this slide

Lysosome containingtwo damaged organelles

TEM

42,

500

Mitochondrion fragment

Peroxisome fragment


4.11 Abnormal lysosomes

Lysosomal storage diseases can be fatal

• Result from an inherited lack of one or more lysosomal enzymes

• Interfere with various cell functions

• Ex. Tay-Sachs Disease, Pompe’s disease


Peroxisomes – break down peroxide

Peroxisomes (microbodies) – break down hydrogen peroxide, made in cell reactions

- other chemical functions in certain cells

- peroxisome disorders include ALD


4.12 Vacuoles store substances

Food vacuoles in paramecium


Plant Cell Vacuole

Large, central vacuole

Stores water and substances needed for photosynthesis

Enzymes to recycle molecules (no lysosomes in plant cells)

LE 4-12a

Centralvacuole

Nucleus

Chloroplast

Col

oriz

ed T

EM 8

,700


Contractile Vacuole

• In some one-celled organisms that live in fresh water

• Water enters cell from environment

• Vacuole pumps out excess water

• Keeps homeostasis

LE 4-12b

Nucleus

LM 6

50

Contractilevacuoles


Review Membrane Organelles4.13 A review of the endomembrane system

• The various organelles of the endomembrane system are interconnected structurally and functionally

• ER is in direct contact with nuclear membrane

• Membrane vesicles transport products from ER to Golgi body, and from Golgi to cell surface

Animation: Endomembrane System

LE 4-13Transport vesiclefrom ER to GolgiRough ER

Nucleus

Smooth ER Nuclear envelope Golgi apparatus

Lysosome

Vacuole

Plasmamembrane

Transport vesicle fromGolgi to plasma membrane


Organelles that capture and release energy

4.14 Chloroplasts –site for photosynthesis Chlorophyll pigment in membrane absorbs sunlight

• Convert solar energy into chemical energy of food

• Plants

• Algae

LE 4-14

ChloroplastStroma

Inner and outermembranes

Granum

Intermembranespace

TEM

9,7

50

Chloroplasts have inner membrane compartments• Each is site for different stage of photosynthesis


Chloroplasts – in plants and algae

Some protists have chloroplasts


Other plastids in plants

Leukoplasts store starch

Chromoplasts store other pigments

-flowers, fruits, seeds

In red pepper

In potato


4.15 Mitochondria – powerhouse of the cell

Site for Cell respiration – converts chemical energy stored in food into ATP for cellular work

• ATP – energy molecule used by all organisms for cell activities

Mitochondria - two membrane compartmentsEach location is site for different stage of glucose breakdown

LE 4-15

Mitochondrion

Intermembranespace

Outermembrane

Innermembrane

Cristae

Matrix TEM

44,

880


Mitochondria and Chloroplasts are different from other organelles

1. double-layered membrane organelles

- inner membrane deeply folded/layered

- large surface area for fast chemical processes

2. have their own DNA and ribosomes

- can self-replicate as needed

- make their own enzymes for reactions


Endosymbiosis Theory – Lynn Margulis

1. Prokaryotes in various sizes, some lost cell wall

2. Larger prokaryotes ate smaller ones

3. Some were not digested but became part of cell

4. Might have survival advantage

Ex. Make its own food; , use energy more efficiently

Evidence to support theory1. Both chloroplasts and mitochondria have their

own DNA and ribosomes – chemically like prokaryotic DNA and ribosomes

2. Can self-replicate3. May have once been separate organisms


Endosymbiotic Theory – How did eukaryotes evolve from prokarytes?


Cytoskeleton4.16 The cell's internal skeleton helps organize its structure and activities

• Protein framework inside cell

• Attaches to cell membrane to keep cell shape

• Anchor organelles

• Transports materials inside cell

• Three kinds: microfilaments , microtubules, and intermediate filaments


c\Cytoskeleton


Microfilaments

Microfilaments

• Rods of globular proteins

• Enable cells to change shape and move

• Cytoplasmic streaming


Microfilaments enable cytoplasmic movement

Cytoplasmic streaming (cyclosis) moves substances around inside a cell

- Some cells can move by pseudopods


Intermediate filaments• Ropes of fibrous protein

• Reinforce the cell and anchor some anchor some organelles

• Hollow tubes of globular proteins

• Give the cell rigidity

• Anchor organelles and act as tracks for organelle movement

• Make centrioles, cilia and flagella

Microtubules


Motor proteins “walk” along microtubules


Proteins in the cytoskeleton

Ropes of fibrous proteins

Anchors some organelles

Reinforces cell

Rods of globular proteins

Cells can move, change shape

Stretch and contract

Hollow tubes of globular proteins

Anchors organelles, tracks for movement

of materials

Rigid shape


cytoskeleton


Cytoskeleton – seen with fluorescent dyes

Microtubules- blue; microfilaments – yellow; chromatin - green


cytoskeleton

The cytoskeleton, a network of protein fibers, crisscrosses the cytoplasm of eukaryotic cells, providing shape and mechanical support. The cytoskeleton also functions as a monorail to transport substances around the cell. A cell such as an amoeba changes shape by dismantling parts of the cytoskeleton and reassembling them in other locations.englishpia.co.kr/main/?page=board&act=view

http://englishpia.co.kr/main/?page=board&act=view&id=photo&no=4220&category=&pg=10


4.17 Cilia and flagella move by microtubules

Eukaryotic cilia and flagella are locomotor appendages that protrude from certain cells

– Move whole cells or materials across the cell surface

Video: Paramecium Cilia

Animation: Cilia and Flagella


Cilia and Flagella

Microtubules extend from cell surface, covered by membrane

Cilia – short, many, like “oars”• Ex. line air passages in body

- cover Paramecium

Flagella – longer, one or a few, move like a “whip”• Ex. Human sperm, euglena


How do microtubules cause movement?

Cilia and flagella - microtubules slide

against each other to cause bending

Basal bodies and centrioles (for cell division)

– don’t bend

Basal body – anchors flagellum

flagellum


Cilia and flagella move when microtubules bend

Movement of protein arms

(dynein) bends microtubules

Ciliated cells in trachea

Flagella on sperm


Centrioles and Spindle Fibers – microtubules

Help in cell division

Centrioles (only in animal cells)

• Organize spindle fibers

• Spindle fibers (in all eukaryotic cells)

– Organize and separate chromosomes when cell divides


Centrioles

Help organize chromosomes for cell division

9 X 3 arrangement of microtubules

Anchor mitotic spindle in animal cells


CELL SURFACES AND JUNCTIONS

4.18 Cell surfaces protect, support, and join cells• Cells interact with their environments and each other

through their surfaces

• Many cells are protected by layers outside the cell membrane

– Prokaryotes –cell wall and sometimes a capsule

– Eukaryotes – some have cell walls (plants, fungi, and many protists)

• Multicellular – cells must organize and communicate


Plant cell walls – provide protection and support• Plant cell walls

– Mostly cellulose, in layers, forms a rigid mesh

– Sticky saccharides glue cells together

– Connect by open channels, plasmodesmata

• Cell membranes and cytoplasm are continuous between adjacent cells

• Easy transfer of water and nutrients

• Chemical messages

LE 4-18a

Vacuole

Wallsof twoadjacentplant cells

Plasmodesmata

Layersof one plantcell wall

Cytoplasm

Plasma membrane


Plant cell walls

Middle lamella – between walls of two plant cells


Animal Cell JunctionsCells are surrounded by an extracellular matrix that binds cells together into a tissue

Cell junctions:

• Tight junctions - bind cells into leakproof sheets (ex. Intestine lining)

• Anchoring junctions - link cells into strong tissues (ex. muscle, skin)

• Gap junctions – open channels allow substances to flow from cell to cell (ex. Heart muscle, embryo)


Extracellular matrix – between animal cells

LE 4-18b

Tight junctions

Anchoring junction

Gap junctions

Extracellular matrix

Space between cells

Plasma membranes of adjacent cells

TIGHT JUNCTIONNo leaks - protect surrounding tissue- ex. Intestine wall

ANCHORING JUNCTIONConnect cytoskeleton of adjacent cells- strong, flexible tissue;

stretch, move- Ex. Skin, muscle

GAP JUNCTIONOpen channels – cells communicate - share needed molecules


Animal Cell Junctions


Animation: Tight Junctions

Animation: Desmosomes

Animation: Gap Junctions


FUNCTIONAL CATEGORIES OF ORGANELLES

4.19 Eukaryotic organelles comprise four functional categories

• Eukaryotic organelles fall into four functional categories that work together to produce the cell's emergent properties

– Manufacturing

– Breakdown

– Energy processing

– Support, movement, and communication between cells

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