Cell Structure and Function

Chapter 4

Robert Hooke (1635-1703)

Discovered “cells” by studying the cork layer of bark from an oak tree.

Found cells when studied tree stems, roots, and leaves.

Antony van Leeuwenhoek (1632-1723)

Learned how to make excellent lenses & placed them into simple microscopes.

He was the first person to observe living cells.

spirogyra

Vorticella

Matthias Schleiden & Theodor Schwann

Schleiden (botanist) & Schwann (zoologist) developed the Cell Theory.

Rudolf Virchow (1821-1902)

Noted that cells come from other cells from studying human diseases.

The Cell Theory

1. All organisms are made up of one or more cells.

2. Cells are the basic unit of structure and function of organisms.

3. New cells come from existing cells by cell reproduction.

MicroscopesLight: light waves

pass through a small organism, or thin slices of a larger organism, & the structures are magnified through the lens system.

Phase contrast: modifies differences in light waves so that transparent cell structures appear as light & dark regions.

Electron: enables us to see cell parts at very high magnifications by using an electron beam instead of a light beam to illuminate the object.

Transmission Electron Microscope: (TEM)

Cell structures can be enlarged as much as 1,000,000x & provides photographs that show remarkable detail.

apoptosis

Cells

Basic unit of living organisms.

2 basic types:

prokaryotes: do not have a membrane enclosing their DNA. Do not contain membrane-bound organelles.

Prokaryotes are divided into two domains:

Bacteria: includes organisms that are similar to the first cellular life-forms.

Archae: includes organisms that are thought to be more closely related to

eukaryotic cells found in all other kingdoms of life.

eukaryotes: usually have at least one membrane enclosed structure, the nucleus, which contains DNA; contain membrane-bound organelles.

unicellular: consists of a single cell which carries out all the many activities of that organism.

multicellular: contain from dozens to billions of cells. Organisms have a number of different types of cells; each type of cell has a certain role to play.

Colonies: a collection of genetically identical cells that live together in a collected group.

Colonies are not truly multicellular since few of their activities are coordinated.

Volvox

Levels of Organization

Cells tissue (group of similar cells that carry out a specific function) organs (group of tissues that perform a particular job in an organism) organ system (group of organs that accomplish related tasks) organism (the combining of organ systems)

Organelles

Structures that carry out specific functions.

Plasma Membrane

• Outer membrane that encloses the cell contents• Controls the passage of materials in & out of the cell• Made of 2 thin layers of lipid molecules.• Protein molecules floating on & within the lipid

layers help molecules move in & out of the cell.

1 - cell-surface marker: glycoprotein that identifies cell type.2 - receptor protein: recognizes and binds to substances outside of cell.3 – intergral protein: enzyme that assists chemical reactions inside cell.4 – transport protein: helps substances move across cell membrane.5 – peripheral proteins: lie on only one side of membrane and not

embedded in it.

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The cell membrane is a fluid mosaic model. The bilayer behaves like a fluid more than a solid. The membrane’s lipids and proteins can move laterally within the bilayer.

Cytoplasm

• Jellylike material found within the cell.• Contains the organelles.• cytosol: includes molecules and small particles but

not membrane-bound organelles.• Many of the chemical reactions of a cell take place in

the cytosol.

Nucleus

• Control center of the cell• Contains most of the cell’s genetic information in

DNA• Contain one or more nucleoli, sites of synthesis &

assembly of rRNA & tRNA• genes: control the basic functions of the cell• chromosomes: contain DNA & proteins

Nuclear Envelope & Nucleolus

• Double membrane surrounding nucleus• It is continuous at several pts. w/a complex network

of other membranes in the cytoplasm

• The nucleolus manufactures ribosomes. It is a knot

of chromatin.

The portion of the cell nucleus which contains all of the DNA of the nucleus in an animal or plant cell.

Endoplasmic Reticulum• Provide passageways for the movement of materials

throughout the cell• 2 types:

RER – Rough Endoplasmic Reticulum

SER – Smooth Endoplasmic Reticulum

RER

• Produces phospholipids and proteins• The ribosomes produce digestive enzymes

SER

• Builds lipids like cholesterol.• Produces estrogen and testosterone.• Releases calcium in skeletal and heart muscle,

which stimulates contractions.• Detoxify drugs and poisons in the liver and kidney

cells.

Ribosomes

Responsible for protein synthesis.

Made of protein and RNA molecules and do not have a membrane.

Mitochondria• Powerhouse of the cell• Transfer energy from organic molecules to

Adenosine Triphosphate (ATP) which powers most of the cell’s chemical reactions.

• Consists of an outer membrane & a folded inner membrane

cristae

Vacuole

Store & transport nutrients & waste products

Golgi Complex

• Helps package cell products for export from the cell

Vesicles

• Small, spherical shaped sac that are surrounded by a single membrane.

• Classified by their contents.• Often migrate to and merge with the plasma

membrane.• Release their contents to the outside of the cell.• “shuttle service”• Include lysosomes and peroxisomes

Lysosomes

Contain digestive enzymes which help break down large molecules & worn-out cell parts

Peroxisomes• Similar to lysosomes but contain different enzymes

and not produced by Golgi Apparatus.• Abundant in liver and kidney cells.• Break down fatty acids, which is then used by

mitochondria.• Produce hydrogen peroxide when breaking down

alcohol and killing bacteria.

Centrioles

Present in pairs and play an important role in mitosis.

Cytoskeleton (Microtubules & Microfilaments)Tiny tubes composed of proteins.

Form the cell’s skeleton

Enable the cell to maintain its distinct shape & internal organization.

Microfilaments contribute to cell movement.

Cell Wall

Provides strength and protection

Formed by living plant cells of cellulose fibers.

Central Vacuole

• Reservoir that stores large amounts of water.• Also stores enzymes, metabolic waste, and

other materials.

Plastids

• Organelles surrounded by a double membrane and contain their own DNA.

2 types:

CHLOROPLASTS

CHROMOPLASTS

ChloroplastsContain the pigment chlorophyll, essential for

capturing the light energy of the sun.

Contain complicated membranes where photosynthesis takes place called thylakoids.

Chromoplasts

• Contain colorful pigments that may or may not take part in photosynthesis.

Carotene: orange pigment found in carrot root cells.

Flower petal cells contain red, purple, yellow. or white pigments.