BASIC UNIT OF LIFE: THE CELL

Chapter 3

All Organisms are made up of cellsEukaryotes- Moth Juniper

Protozoans Ciliates in water on plant

Prokaryotes Bacteria in insect gut and on surface of insect and tree

Cell theory

All living organisms are made up of cells

All cells come from other cells

Theory refers to the body of knowledge that has been developed through scientific inquiry

Two Cell Categories

Prokaryote Eukaryote Cell membrane Cytoplasm DNA (in a loop) Ribosomes (for

creating proteins) Cell wall Very small DNA is loose in

cytoplasm

Cell membrane Cytoplasm DNA (in strands) Ribosomes Many other organelles Cell wall in plants Variable size – larger

than prokaryotes Nucleus holds DNA

The organisms that cause colors in the hot springs of Yellowstone are single celled and have been around since the beginning of life on this planet. Would these organisms be prokaryotes or eukaryotes? Would their cells have a nucleus?

A. Prokaryotes, yesB. Prokaryotes, noC. Eukaryotes, yesD. Eukaryotes, no

http://serc.carleton.edu/microbelife/extreme/extremeheat/yellowstone.html

Basic Cell Structures

Cell Membrane Nuclear double

membrane around nucleus

Mitochondria for energy

Processing and packaging organelles

Lysosomes – digestion Cytoskeleton - support

Plasma Membranes

Bilayer Structure

Molecules Found in the cell Membrane

Cholesterol increases membrane flexibility

Types of Membrane Proteins

1. Receptor proteins – Bind to external molecules which cause reactions in

cell Ex. Target cells can detect hormones in blood –

regulate development of secondary sexual characteristics

2. Recognition proteins Typically have attached carbohydrate chains Give the cell identity – other cells can recognize them Ex. During development cells interact & work together

to develop structures. Recognition is essential. Ex. Autoimmune disease = faulty self-recognition

Visual examples

Receptor proteins Recognition proteins

Types of Membrane Proteins3. Transport proteins

Move other molecules across the cell membrane

Transmembrane proteins only Ex. Nerve cell fire – Na ions moved across

4. Enzymatic proteins Increase rate of chemical reactions

associated with the cell membrane Ex. cAMP formation regulated – internal

messenger created

Visual Examples

Transport proteins Enzymatic proteins

Why is the cell membrane considered a fluid mosaic?A. It’s primarily made up of water with

dispersed fats and proteins in a mosaic pattern

B. Proteins move back and forth through the membrane from inside to outside of the cell and back in a fluid mosaic pattern.

C. It’s made up of several different types of molecules, like a mosaic, and many of those molecules float around in the lipid bilayer.

Cell Structure and Function Cells are factories

Need raw materials to enter the cell Need to eliminate wastes Need to export products produced in the

cell Need to keep up-to-date on needs of

surrounding cells and tissues

Endocytosis

Exocytosis

Animation of endocytosis and exocytosis

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio02.swf::Endocytosis%20and%20Exocytosis

Other means of movement

Passive Transport Active Transport Requires no input

of energy

Diffusion Osmosis (diffusion

of water across a membrane)

Requires energy input to move molecules across the cell membrane or around in the cell

Primary – uses ATP Secondary

DiffusionKey: Molecules tend to move from an area of high concentration to an area of low concentrationWhen moving across a membrane – diffusion may be facilitated by a transport protein

Osmosis

Irrigation problems

Irrigation can lead to a build up of soil salinity

If soil develops a similar (or higher) salt content than the plant cells, water doesn’t flow as easily into plant roots. Soil salt concentrations make plants and soil

more alike in fluid concentration (isotonic) - so water doesn’t flow across the cell membranes into the plant roots.

Soil salinity creates drought like conditions in which plants can’t get water

PassiveTransport

Active Transport

The object depicted in the figure:

A) is a bacterial cell.B) could be either a plant or an animal cell.C) is a ribosome. D) is an animal cell.E) is a plant cell.

Cell Wall

Not found in animals

A major component of the cell wall is

the complex carbohydrate,

Cellulose

If the concentrations of a particular molecule are equal on both sides of the membrane, facilitated diffusion will:

A) insure that the molecule becomes concentrated outside the cell.B) insure that the molecule stays impermeable to the membrane.C) insure that the molecule becomes concentrated inside the cell.D) insure that the concentrations inside and outside the cell are both increased.E) be ineffective.

Connections Between Cells:

1. Tight Junctions

> hold cells in place> keep fluids from passing around edges of cells

blood brain barrierlining of gut

Connections Between Cells:

2. Desmosomes

> throughout body

Connections Between Cells:

3. Gap Junctions

>Allows small molecules, but not large proteins and organelles to move between cells.

Cell Size

Chicken egg = 40-60 mm (1mm = 1/1000 m)

Paramecium caudatum = 60X 230 um (1 um = 1/1000 mm)

Red blood cell = 1.9-7.5 um Bacteria 0.5-2 um

Why not bigger?

Ostrich

What limits the size of cells?

Much of what occurs in a cell depends on the movement of materials in and out of the cell through the plasma membrane

Rate of production and waste removal is dependent on cell volume

Rate of movement across the membrane depends on surface area of cell

As cell size increases, volume increases as a cubed unit while surface area as a square unit.

Surface to volume ratio

Radius 1 cm 2 cm 3 cmSurface area (cm2)

12.57 50.26 201.06

Volume (cm 3)

4.19 33.51 268.08

SA/V 3 1.5 0.75

Nucleus and chromosomes

Cytoskeleton

Made up of protein fibers that can expand, contract, move past one another.

Microfilaments underlie the cell membrane and cytoskeletal elements can break down and reform to allow changing shape in Amoeba.

Cell locomotion:

Mitochondria – have own DNA!

Mitochondria con’t

Number in a cell may vary Cells with high energy demands like

muscles have more than other cells Process known as aerobic respiration

(Kreb cycle & electron transport phosphorylation) takes place here. Sugar (C6H12O6) + 6H2O + 6O2 => 6 CO2 + 12 water

(H2O) + Energy Breaks down sugar to release the energy in the

chemical bonds Oxygen is used and Carbon dioxide is a waste

biproduct.

Chloroplasts

Only in Plant Cells and Single-celled Algae

Have own DNA!

Similar in some ways to bacteria that do photosynthesis – especially DNA

Evolution of Eukaryote Cells

Lysosomes – Waste removal

Up to 50 different types of enzymes!

Endoplasmic Reticulum

Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum

Golgi Apparatus

Vacuoles

Cells can be Single-celled Organisms

Euglena can engulf other organisms or do photosynthesis to get food for building blocks and energy. Eyespot Flagellum Contractile Vacuole

Cells Specializations Within a Multicellular

Organism All cells have the same genetic material.

Cells specialize because some genes are turned off and others are turned on.

Ex. Lining of small intestine

Ex. Nerve cell

Design Organelle Analogies Analogy

Includes similes and metaphores Similes compare things using words “as”

or “like” Ex. You are as stubborn as a mule. Ex. Life is like a box of chocolates.

Metaphores compare 2 unlike things for secondary meaning Ex. The gum was bursting with flavor. Ex. The relationship between them began

to thaw.

The organelle in the figure is found in:

A) animals only.B) plants only.C) plants, animals, and bacteria.D) plants and animals.E) bacteria only.

What is it?

The lysosomes in a human cell contain approximately ________ different type(s) of digestive enzymes.

A) 1B) 500C) 10D) 4E) 50

According to the theory of endosymbiosis, the origin of chloroplasts probably involved:

A) the formation of cell walls around the photosynthetic pigments.B) the formation of colonies of cyanobacteria.C) the engulfing of small photosynthetic prokaryotes by larger cells.D) the accumulation of free oxygen in ocean waters.E) All of the above are correct.

Read chapter 4 on Energy