1

Chapter 7 Cellular Structure and Function

7.1 Cell Discovery and Theory

2

The History of the Cell Theory

Cells are the basic units of living things

Before microscopes people believed diseases were caused by curses and supernatural spirits (wrath of God)

The idea that a living thing like a bacteria could cause disease or infection never occurred. Why?

3

Development of the Light Microscope

Today's microscope is a compound microscope with two lenses Eyepiece lens Objective lens

Can magnify 1500 times

4

Simple Light Microscope

Developed by Anton van Leeuwenhoek in the mid 1600

One lens Much like a

magnifying glass

5

The Cell Theory

Robert Hook First to use the

term “cell” Looked a cork

under a microscope, saw the cell walls

6

Robert Hook

Contemporary of Anton van Leeuwenhoek

English Published and

encouraged others to use microscopes

7

Matthias Schleiden

1838 German botanists Examined plants of

all types All plants are

made of cells

8

Theodore Schwann

1839 German zoologist Contemporary of

Schleidens Examined animal

tissues of many types

All animals are made of cells

9

Rudolph Virchow

1855 German physician All cells come from

preexisting cells

10

The Cell Theory

1. All organisms are composed of one or more cells

Unicellular or multicellular

2. The cell is the basic unit of organization of all organisms

Structure Function

3. All cells come from preexisting cells

11

Technology Since the 1800’s

Compound light microscopes continued to improve so that bacteria were able to be classified

Most magnification possible with light microscopes cannot see inner cell parts

12

Electron Microscopes

Developed in the 1940’s Uses magnets to focus a beam of

electrons (in place of light) Can magnify 500,000X Several types

Scanning: looks at surface; get 3-D Transmission: looks at interior Scanning-Tunneling: atoms on surface

13

Microscope Aids

Both light and electron microscopes use dyes and stains which helps to contrast cell and parts

Most dyes and stains kill the cells Most specimens of electron

microscopes need to be in a vacuum and/or coated with gold

14

Two Basic Cell Types

Prokaryote Have plasma

membrane No internal membrane

bound structures Unicellular Smaller in size No specialization Example: bacteria

Eukaryote Have plasma

membrane Internal membrane

bound structures Unicellular and

multicellular Larger size Much specialization Example: animal

15

Two Basic Cell Types

Prokaryote Eukaryote

16

Two Basic Cell Types

17

Chapter 7 Cellular Structure and Function

7.2 The Plasma Membrane

18

Plasma Membrane Diagram

19

Plasma Membrane Micrograph

20

Plasma Membrane Structure

Made of phospholipid bilayer

Polar ends are hydrophilic

Nonpolar ends are hydrophobic

21

Plasma Membrane Function

Job of plasma membrane is homeostasis- maintain balance

For cells to survive they must keep the inside in and the outside out, yet allow some materials to move into and out of the cell

22

Structure Fits Function

The structure of the plasma membrane (how it is put together) allows the plasma membrane its function or job, selective permeability

Selective permeability: the ability to allow some materials into or out of the cell but not other materials

23

Selective Permeability

Out side of cell is different from inside of cell

24

Structure Fits Function

Both the inside of the cell and the outside are water environment so the hydrophilic ends face in and out

The hydrophobic fatty tails are in the middle so that materials can’t pass through easily

25

Structure Fits Function

Role of proteins in plasma membrane Channels or tunnels for substances

to pass through with specific fit Identification of organism and tissue

type Signal sending proteins Provide support for the

phospholipids

26

Plasma Membrane Proteins

27

Plasma Membrane

Cholesterol stabilizes the plasma membrane in animal cells

Animal cells have no cell wall as do plant cell

High blood cholesterol is a risk factor for heart disease and stroke

Animals (including us) produce cholesterol for the stabilization of the cell membrane

28

Fluid Mosaic Model

29

Fluid Mosaic Model

FLUID: Plasma membrane in constant motion with the phospholipids of one layer moving one direction and the phospholipids of the other layer moving in the opposite direction

MOSAIC: something consisting of a number of different things of different types

30

Chapter 7 Cellular Structure and Function

7.3 Structures and Organelles

31

Cellular Boundaries

Plant Cell outer most part is the cell wall; plasma membrane is inside of the cell wall

Also fungi, algae and other Kingdom Protista organisms

Animal Cell outer most part is the plasma membrane

Also protozoans (Kingdom Protista)

32

Cell Wall

Functions to protect and support NOT selectively permeable Porous: let anything in Plant cell wall made of cellulose

(wood)

33

Plant Cell Wall

34

Nucleus

Controls all cell activities

Contains information to make proteins; all parts of the cell depend on proteins to do its job

35

Nucleus

Contains DNA in strands known as chromatin (chromosomes are chromatin that is condensed and visible during cell reproduction)

36

Nucleolus

Found in the nucleus

Organelle that makes ribosomes

Ribosomes are sites where proteins are manufactured

37

Ribosomes

Ribosomes are unique because they do not have a membrane around them

Found in prokaryotes and eukaryotes

Look like pepper on the ER (spaghetti)

38

Nuclear Membrane

Also called Nuclear Envelope

Surrounds the nucleus

Same composition as the plasma membrane

Contains pores to allow large materials to pass out (ribosomes and RNA)

39

Cytoplasm

All the gelatinous material with the organelles inside the cell between the nucleus and the cell membrane

Cytosol is that part of the cytoplasm that is liquid

40

Organelles for Assembly, Transport and Storage

Endoplasmic Reticulum (ER) Golgi Apparatus Vacuoles Lysosomes

All have phospholipid bilayer membrane structure

41

Endoplasmic Reticulum (ER)

Folded membrane like an accordion for workspace

Rough ER contains ribosomes for protein production

Smooth ER (No ribosomes) for lipid production

Tube-like for transport of materials

42

Golgi Apparatus

Takes protein from the ER and makes it ready to be transported

Like UPS, packages it and gives it a destination address

43

Vacuoles

Large central vacuole in plant cells to store water

Smaller vacuoles for storage of food, waste, water, enzymes and other substances in both plant and animal cells

44

Lysosomes

Double membrane bound sac containing digestive enzymes

Digests food particles, engulfed viruses and bacteria, and worn out cell parts

Can fuse with vacuole to digest contents of vacuole

45

Energy Transformers

Chloroplasts Mitochondria

Both have phospholipid bilayer membrane structure

46

Chloroplasts

Capture light energy and produce food to be used later

Pigment chlorophyll give plants their green color

Other plastids store starch, lipids and other pigments

47

Chloroplasts

Double membrane Clear outer Folded inner:

thylakoid Stacks of

membranes sacs grana and liquid stroma

Site of photosynthesis

48

Mitochondria

Break down food to release energy

Found in eukaryotes

49

Mitochondria

Double membrane Outer Folded Inner to

increase membrane space

Some cells need much energy and have hundreds of mitochondria; other cell have few mitochondria because these cells use little energy

Site of cellular respiration

50

Structures for Support and Locomotion

Cytoskeleton Cilia Flagella

51

Cytoskeleton

Internal framework in the cell to keep the organelles in place

Maintains the cell’s shape

Made of microtubules (hollow) and microfilaments (solid) protein fibers

Shown in green

52

Centrioles

Made of groups of microtubules

Function in cell division (Ch. 9)

53

Cilia and Flagella

Enclosed by plasma membrane

Used for locomotion and feeding

Made of pair of microtubules surrounded by 9 additional pairs

54

Cilia

Short numerous hair like projections

Beat like oars on a boat

Line our respiratory system

55

Flagella

Tail like structure that is whip like

May have one flagella or several

Mostly used for locomotion

56

Chapter 7 Cellular Structure and Function

7.4 Cellular Transport

57

Passive Transport

NO energy expended by cell

Diffusion Facilitated

diffusion Osmosis

58

Diffusion

All molecules are in constant motion; called Brownian Motion

The high the temperature the faster the motion because they have more energy

Diffusion is the net movement of particles from higher concentration to lower concentration because of this movement of particles

Diffusion is slow because it is a random process

59

60

Rates of Diffusion

1. Concentration of substances involved More concentrated substances speed up rate of

diffusion

2. Energy by temperature or agitation Increased temperature speeds up rate of

diffusion Agitation or stirring speeds up rate of diffusion

3. Pressure Increased pressure speeds up diffusion because

pressure increases molecular movement

61

Dynamic Equilibrium

Equilibrium is reached when there is no net concentration change

Dynamic because Brownian motion continues

62

Diffusion in Living Systems

In living things materials must diffuse into and out of cells all the time

Concentration gradient exists so that substances will move into the cell until there is the same number on each side

Liquids, solids and gasses can diffuse into and out of a cell

63

Facilitated Diffusion

Diffusion of materials through proteins in cell membranes

NO energy required

Common for sugars and amino acids

64

Osmosis

Diffusion of water through a cell membrane

Cell membranes are selectively permeable

NO energy expended by the cell Moves water from high

concentration to low concentration Must occur for homeostasis to occur

65

Control of Osmosis

Unequal distribution of particles on either side of a selectively permeable membrane

Water moves through the membrane until equilibrium is reached (no net change)

66

Cells in Solutions

Isotonic Solution = same solutes Hypotonic Solution = lower solutes Hypertonic Solution = higher solutes

67

Cells in Isotonic Solutions

Isotonic solutions have the same solute concentration as the cell, so water moves in and out at the same rate; no osmosis; no net change

Dissolved substances outside the cell equals dissolved substances inside the cell

Examples: Normal saline IV solution (0.9% salt) and tap water in most areas

68

Cells in Hypotonic Solutions

Dissolve substances lower outside the cell than inside the cell

Water moves into the cell; cell swells Animal cell bursts Plant cell becomes more firm (higher

turgor pressure); reason why plants are sprayed at grocery store

Example: Distilled water

69

Cells in Hypotonic Solutions

70

Cells in Hypertonic Solutions

Dissolved substances higher outside the cell than inside the cell

Water leaves the cell; cell shrinks Animal cell wrinkled (reason why meat

is salted after cooking) Plant cell plasmolyzed; cell membrane

moves away from cell wall Example: salt water, syrup

71

Cells in Hypertonic Solutions

72

Cells in Solutions

73

Comparing Plant and Animal Cells

74

Active Transport

ENERGY used by the cell Carrier proteins with a SPECIFIC FIT

with a specific molecule Bringing substances into the cell

against the concentration gradient

75

Active Transport

When molecule fits with carrier protein the carrier protein molecule changes shape to allow the molecule to move into or out of the cell

When movement complete, the carrier protein changes back to original shape for another molecule

76

Active Transport

Also used to rid the cell of materials against the concentration gradient

Takes energy to use a pump

Much of your cell’s energy is expended in the sodium-potassium pump (2 K+ in 3 Na+ out)

77

Large Materials Into Cells

Endocytosis, getting large materials INTO the cell

Cell expends energy

Engulfs and forms a vacuole

Example: white blood cells engulfing a bacteria

78

Large Materials Out of Cells

Exocytosis: large materials out of a cell

Cell expends energy

Example: secretions or hormones

Example: waste products

79