cell organelles 1

1

Cyto-biology

Overview of the cell

Describe the organelles of cells and give the function of each

Identify the differences between plant and animal cells

Describe the differences between prokaryotic and eukaryotic cells

Last time…

3

Organelles of the eukaryotic cell

Structure of the cell related to function.

4

Section 1

The typical cell: vital statistics and compo-sition.

5

Objectives

Describe a typical eukaryotic cell. Describe the chemical composition of a cell. Summarize the work of cells.

bacteriacellsbacteriacells

Types of cells

animal cellsanimal cells plant cellsplant cells

Prokaryote- no organelles

Eukaryotes- organelles

Cell size comparison

Bacterial cellAnimal cell

micron = micrometer = 1/1,000,000 meter diameter of human hair = ~20 microns

most bacteria 1-10 microns

eukaryotic cells 10-100 microns

Why study cells?

Cells Tissues Organs Bodies bodies are made up of cells cells do all the work of life!

9

Typical eukaryotic cell

Cell size is 10-100 m in diameter Cell mass is 1 nanogram Two major parts:

nucleus cytoplasm

The nucleus is separated from the cytoplasm by the nuclear mem-brane.

The cytoplasm is separated from the surrounding fluids by the cell membrane.

10

What…

…is the biggest cell in the human body?

The ovum, which is 120-150 m in

diameter.

The Work of Life

“breathe” gas exchange: O2 in

vs. CO2 out

eat take in & digest food

make energy ATP

build molecules proteins, carbohy-

drates, fats, nucleic acids

remove wastes control internal

conditions homeostasis

respond to external environment

build more cells growth, repair, re-

production & devel-opment

ATP

What jobs do cells have to do for an organism to live?

Cells have 3 main jobs make energy

need energy for all activities need to clean up waste produced

while making energy make proteins

proteins do all the work in a cell, so we need lots of them

make more cells for growth to replace damaged or diseased cells

The Jobs of Cells

Our organellesdo all these

jobs!

ATP

Organelles

Organelles do the work of cells each structure has a job to do

keeps the cell alive; keeps you alive

Model Animal Cell

They’re likemini-organs!

14

Organelles in plants and an-imals

JOBS OF CELLS make energy make proteins

make more cells

cell membranelysosomesvacuolesvesiclesmitochondria

nucleusribosomesendoplasmic reticulumgolgi aparatus

cytoskeletoncentrioles

15

Organelles in plants and an-imals


make more cells

cell membranelysosomesvacuolesvesiclesmitochondria

nucleusribosomesendoplasmic reticulumgolgi aparatus

cytoskeletoncentrioles

16

Section 2

Cell Organelles: The Cell Membrane

17

Objectives

Describe the structure of a cell membrane / plasma membrane.

Give the chemical composition of a cell membrane.

Explain the various transport methods in which substances pass the cell membrane.

Give examples of each of the transport methods.

Cells need power! Making energy

to fuel daily life & growth, the cell must… take in food & digest it take in oxygen (O2) make ATP remove waste

organelles that do this work… cell membrane lysozomes vacuoles & vesicles mitochondria

ATP


make more cells

cell membranecell boundarycontrols movementof materials in & out

recognizes signals

cytoplasmjelly-like material holding

organelles in place

Structure double layer of fat

phospholipid bilayer receptor molecules

proteins that receive signals

Cell membrane

lipid “tail”

phosphate“head”

separates cell from outside controls what enters or leaves cell

O2, CO2, food, H2O, nutrients, waste recognizes signals from other cells allows communication between cells

Function of the cell mem-brane

22

The structure of a cell mem-brane

Also called the plasma membrane or plasmalemma. A thin, pliable, very elastic structure. Only 7.5-10nm thick. It envelopes the cell

Helps to maintain the structural and functional integrity of the cell

Sensory device It recognizes other cells and macromolecules

It has a trilaminar structure called “the unit mem-brane”.

23

The lipid bi-layer

Trilaminar structure looks like 3 layers

Mainly composed of a lipid bilayer with a large number of protein mole-cules.

Most of the membrane proteins are glycoproteins

24

Chemical composition

Proteins (55%) Integral proteins Peripheral proteins

Carbohydrates (3%) Proteoglycans Glycocalyx

Phospholipids (25%) Consist of phosphate heads and two fatty acid tails

Cholesterol (13%) Other lipids (4%)

glycolipids

Percentage

Proteins Carbo-hydrates

Phospholipids CholesterolOther lipids

http://www.youtube.com/watch?v=moPJkCbKjBs

http://www.youtube.com/watch?v=moPJkCbKjBs

Lipid Molecules

http://www.youtube.com/watch?v=7k2KAfRsZ4Q

polar head groups positioned towards

water

glycerol core

hydrophobic non-polar

tails hide in the middle

http://www.youtube.com/watch?v=7k2KAfRsZ4Q

28

The cell membrane is semi-per-meable

Only some substances can pass the membrane

The middle of the phospho-lipid bilayer is non-polar Only other non-polar molecules

can get through, such as fats and other lipids.

Water, other polar molecules, ions and large molecules can’t get through.

29

Protein channels

Protein channels make a mem-brane semi-permeable.

Certain channels allow certain molecules across to enter the cell.

30

Transport through cell membranes

31

Transport through cell mem-branes

There are 4 basic mechanisms:

DIFFUSION and FACILITATED DIFFUSION

OSMOSIS

ACTIVE TRANSPORT

BULK TRANSPORT Endocytosis Exocytosis

32

Diffusion

Diffusion is the net movement of molecules from a region of higher concentration to t region of lower concentration.

The molecules move down a con-centration gradient.

33

Diffusion All molecules are in constant motion Molecules have kinetic energy, which

makes them move about randomly. As a result of diffusion molecules reach

an equilibrium where they are evenly spread out.

This is when there is no net movement of molecules

http://www.youtube.com/watch?v=gXJMBgyT_hkhttp://www.youtube.com/watch?v=gXJMBgyT_hk

http://www.youtube.com/watch?v=gXJMBgyT_hk

http://www.youtube.com/watch?v=gXJMBgyT_hk

34

Diffusion of liquids

Diffusion through a membrane

35

Cell membrane

Inside cell Outside cell

A concentration gradient exists.

All molecules have kinetic energy and can move about.

The molecules which are small enough can move through the cell membrane.Movement is passive. No additional energy is needed. High

concentrationLow concentration

36

Diffusion through a membraneCell membrane


diffusion

Equilibrium is reached

37

Cell membrane


EQUILIBRIUM

39

Diffusion of more than one solute happens at the same time

40

The rate of diffusion is determined by 4 factors:

1.The steepness of the concentration gradient.

2.Temperature3.The surface area. 4.The type of molecule or ion diffusing.

41

The steepness of the concen-tration gradient

The bigger the difference between the two sides of the membrane the quicker the rate of diffusion.

Higher rate of diffusion

42

Temperature

Higher temperatures give mo-lecules or ions more kinetic energy. Molecules move around faster, so diffusion is faster.

Higher rate of diffusion

warmer cooler

43

Surface area

The greater the surface area the faster the diffusion can take place. This is because the more mo-lecules or ions can cross the mem-brane at any one moment.

44

Type of molecule or ion

Large molecules need more energy to get them to move so they tend to diffuse more slowly.

Non-polar molecules diffuse more easily than polar molecules be-cause they are soluble in the non polar phospholipid tails.

Molecules that diffuse through cell membranes

1. Oxygen – Non-polar so diffuses very quickly.

2. Carbon dioxide – Polar but very small so diffuses quickly.

3. Water – Polar but also very small so diffuses quickly.

45

46

Facilitated diffusion

Large polar molecules such as glucose and amino acids, cannot diffuse across the phospholipid bilayer. Also ions such as Na+ or Cl- cannot pass.

These molecules pass through protein channels in-stead. Diffusion through these channels is called FACILITATED DIFFUSION.

Movement of molecules is still PASSIVE just like or-dinary diffusion, the only difference is, the mo-lecules go through a protein channel instead of passing between the phospholipids.

48

Facilitated diffusion through a mem-brane

Cell membrane


Protein channel


49

Cell membrane


Protein channel

diffusion

50

Cell membrane


Protein channel

diffusion

EQUILIBRIUM


51

Facilitated Diffusion:

Molecules will ran-domly move through the open-ing- like pore, by diffusion.

This requires no en-ergy, it is a PASSIVE process.

Molecules move from an area of high concentration to an area of low conc.

52

Example of passive facili-tated transport

Glucose Transporter Protein (G-LUT1)

53

Glucose Transport intoerythrocyte by GluT1

The transporter exists in 2 conformations. T1: Glucose binding site

exposed on outer sur-face

http://www.biochem.arizona.edu/classes/bioc462/462a/NOTES/LIPIDS/transport.html

54


The transporter exists in 2 conformations. T1: Glucose binding site

exposed on outer sur-face

T2: Binding site exposed on inner surface


55


D-glucose binds on the outside of the stereo-spe-cific binding site on T1.

The binding of glucose causes a conformation change.

The conformation changes to T2, which allows the glucose to be released on the inside of the cell.

http://www.youtube.com/watch?v=GFCcnxgXOhY



56

Osmosis

‘The diffusion of water from an area of high concentration of water molecules (high water potential) to an area of low concentration of water (low water potential) across a par-tially permeable membrane.’

57

OsmosisCell membrane partially permeable.

Inside cell Outside cellVERY High conc. of water molecules. VERY high water potential.

VERY Low conc. of water molecules. VERY low water potential.

Sugar molecule

DILUTE SOLUTION CONCENTRATED SOLUTION

Please correct

58


Inside cell Outside cellHigh conc. of water molecules. High water potential.

Low conc. of water molecules. Low water potential.

OSMOSIS

59



OSMOSIS

EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water

water:sugar ratio is

important!!

60

Effects of osmosis

63

Water can move through protein channels

Protein channels for water are called aqua-porins

Water can mover through the cell mem-brane at a very high rate

64

Summary of passive transport

http://www.youtube.com/watch?v=JShwXBWGMyY&feature=fvwrel



65

Active transport Material is moved

from low concentra-tion to high concen-tration through a membrane

Carrier protein is used, so it is facili-tated transport

ATP is required

66

Examples of active transport

Sodium-Potassium pump

67

Sodium-potassium pump

http://www.youtube.com/watch?v=GTHWig1vOnY&feature=related



68

Facilitated Transport

69

Active and passive transport http://www.youtube.com/watch?v=

kfy92hdaAH0&feature=relmfu

http://www.youtube.com/watch?v=9wiPhcKlhTw&feature=related

http://www.youtube.com/watch?v=kfy92hdaAH0&feature=relmfu

http://www.youtube.com/watch?v=kfy92hdaAH0&feature=relmfu

70

Cotransport also uses the process of diffusion. In this case a molecule that is moving naturally into the cell through diffusion is used to drag another molecule into the cell. In

this example glucose hitches a ride with sodium.

71

These are carrier proteins. They do not extend through the membrane. They bond and drag molecules through the bilipid layer and release them on the opposite side.

72

In summary

73

Bulk Transport

AS Biology, Cell membranes and Transport


74

Vesicle-mediated transport Vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter a cell. Exocytosis is the term applied when transport is out of the cell.

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossV.html

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossV.html

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookglossE.html

75

Exocytosis

Large molecules that are manufactured in the cell are released through the cell membrane.

76

Endocytosis

The cell membrane can also engulf structures that are much too large to fit through the pores in the membrane proteins.

In this process, the membrane itself wraps around the particle and pinches off a vesicle inside the cell.

Amoeba engulfs a food particle

77

Endocytosis – Exocytosis

78

Types of Endocytosis

Phagocytosis

Pinocytosis Receptor-mediated

endocytosis

http://www.mcatzone.com/glosslet.php?letter=p&pagenum=2

79

Types of Endocytosis

80

Phagocytosis

http://www.nlm.nih.gov/medlineplus/ency/imagepages/9478.htm

81

Phagocytosis

http://www.answers.com/topic/phagocytosis

82

Phagocytosis


83

Phagocytosis for food in-take

84

Example of phagocytosis

Tularemia infection


85

Tularemia (rabbit fever)

Tularemia is a disease commonly found in rodents.

It is caused by a bacterium, Francisella tularensis.

Phagocytosis has been proposed as the mode of infection of the bacterium.

86

A model for infection by Francisella tu-larensis


87

Examples of receptor-me-diated endocytosis

1. Endocytosis of cholesterol2. Endocytosis of a virus particle

(model)

88

Endocytosis of cholesterol

LDL particles bind to specific LDL receptors in coated pits of the cytoplasmic membrane. The coat on the inner surface of the membrane is a layer of a protein called clathrin.

http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/rmendo1.html

89

A coated vesicle forms by endocytosis.

90

The clathrin coating detaches from the vesicle and is recycled back to the cytoplasmic membrane. The uncoated vesicle is called an endosome.

91

The endosome divides forming two vesicles.

92

One vesicle recycles the LDL receptor proteins to the cytoplasmic membrane. The other vesicle fuses with lysosomes.

93

After the vesicle fuses with the lysosome, the contents are digested and free cholesterol is released into the cytosol.

94

Summary of endocytosis

A schematic illustration of the receptor-mediated endocytosis and viral budding processes.

Bao G , Bao X R PNAS 2005;102:9997-9998©2005 by National Academy of Sciences

Model for endocytosis of a virus

96

Resources http://www.biochem.arizona.edu/classes/bioc462/462a/NOTES/LIPIDS/transpo

rt.html http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/cmeu.html#rme



http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/cmeu.html

97

This PowerPoint was originally downloaded from www.worldofteaching.com

But extensive changes and additions have been made to the material.

http://www.worldofteaching.com/

cell organelles 1

Documents

Transcript of cell organelles 1