Cell Structure & Function

•Robert Hooke (1600s) named the cell after viewing cork under m’scope

At 40x tattoo ink in dermis of skin

http://micro.magnet.fsu.edu/cells/plants/plantmodel.html

http://micro.magnet.fsu.edu/cells/animals/animalmodel.html

Comparing Prokaryotic and Eukaryotic Cells

• Basic features of all cells: – Plasma membrane– Semifluid substance called cytosol– Chromosomes (carry genes)– Ribosomes (make proteins)

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

2 Types of Cells

• Prokaryotes: earliest cells;

Have NO NUCLEUS

• Eukaryotes: modern cells/most

cells( all but bacteria)

HAVE A NUCLEUS

Fig. 6-6

Fimbriae

Nucleoid

Ribosomes

Plasma membrane

Cell wall

Capsule

Flagella

Bacterialchromosome

(a) A typical rod-shaped bacterium

(b) A thin section through the bacterium Bacillus coagulans (TEM)

0.5 µm

Sickle Cell Anemia *note misshapen RBC

Cell Theory

1. All living things are made of cells.

2. Cells are the basic unit of life

3. New cells come from existing cells

-Schleiden, Schwann, Virchow

Functions of Organelles

Cytoplasm(Cytosol)

• Thick, clear gel-like substance found throughout cell

• Supports the organelles

Nucleus

• “control center” of cell• Contains the chromosomes (genetic info.= DNA*)• Has all instructions to make new

proteins• *DNA from both parents found

here

Nucleolus

• Center of nucleus

• Site of ribosome synthesis

(ribosomes are made here)

Fig. 6-UN1a

Cell Component Structure Function

Concept 6.3 The eukaryotic cell’s geneticinstructions are housed inthe nucleus and carried outby the ribosomes

Nucleus Surrounded by nuclearenvelope (double membrane)perforated by nuclear pores.The nuclear envelope iscontinuous with theendoplasmic reticulum (ER).

(ER)

Houses chromosomes, made ofchromatin (DNA, the geneticmaterial, and proteins); containsnucleoli, where ribosomalsubunits are made. Poresregulate entry and exit osmaterials.

Ribosome Two subunits made of ribo-somal RNA and proteins; can befree in cytosol or bound to ER

Protein synthesis

Fig. 6-10

NucleolusNucleus

Rough ER

Nuclear lamina (TEM)

Close-up of nuclear envelope

1 µm

1 µm

0.25 µm

Ribosome

Pore complex

Nuclear pore

Outer membraneInner membraneNuclear envelope:

Chromatin

Surface ofnuclear envelope

Pore complexes (TEM)

Chromosomes

• Contain genetic information/DNA

• Chromatin combines to form

• Humans have 46 chromosomes or 23 pairs

Fig. 15-1

Fig. 15-5

X

Y

Endoplasmic Reticulum

• Extensive system of tubules and membranes

–2 Types:

1.Smooth ER

2.Rough ER

Smooth ER

• Synthesis of lipids (cholestrol)

• Breaks down/metabolizes carbohydrates

• Packages enzymes for secretion

• De-toxification of alcohol in liver ER

Fig. 6-12

Smooth ER

Rough ER Nuclear envelope

Transitional ER

Rough ERSmooth ERTransport vesicle

RibosomesCisternaeER lumen

200 nm

Fig. 6-11

Cytosol

Endoplasmic reticulum (ER)

Free ribosomes

Bound ribosomes

Large subunit

Small subunit

Diagram of a ribosomeTEM showing ER and ribosomes

0.5 µm

Rough ER

• Has ribosomes attached

• One of the sites of protein assembly

Ribosomes

• Site of protein synthesis • Made of RNA + protein• Means: proteins are made here• Free Ribosomes: NOT attached

to ER• Bound Ribosomes: attached to

ER

Cell Membrane(plasma membrane)

•Support

•Protection

•Regulates which substances enter & exit = Selectively

permeable

Fig. 6-7TEM of a plasmamembrane

(a)

(b) Structure of the plasma membrane

Outside of cell

Inside ofcell 0.1 µm

Hydrophilicregion

Hydrophobicregion

Hydrophilicregion Phospholipid Proteins

Carbohydrate side chain

Fig. 6-30

EXTRACELLULAR FLUIDCollagen

Fibronectin

Plasmamembrane

Micro-filaments

CYTOPLASM

Integrins

Proteoglycancomplex

Polysaccharidemolecule

Carbo-hydrates

Coreprotein

Proteoglycanmolecule

Proteoglycan complex

What might ENTER a cell?

• Oxygen

• Dissolved nutrients

• Potassium and other ions

• water

Vacuoles

• Storage of –Water

–Dissolved nutrients

–Even Waste

**animals have few, very small

Fig. 6-15

Central vacuole

Cytosol

Central vacuole

Nucleus

Cell wall

Chloroplast

5 µm

Central Vacuole

• Plants have a large central vacuole.

• Takes up most of plant cell–Supports

–Turgor Pressure

–“Wilting” process: how?

Nuclear Membrane

• Protects nucleus (why necessary?)

• Has Nuclear Pores: holes to allow substances to enter/exit

Lysosomes

• Animal Cells

• Bags of hydrolytic enzymes

• Digests old cell organelles

Cytoskeleton

• System of protein fibers• (Microtubules,

microfilaments)1. Gives cell shape2. Supports cell3. Helps move organelles

Fig. 6-1

Golgi ApparatusGolgi Body

• Proteins are modified and packaged here for secretion

• “warehouse/UPS” of cell

• Lysosomes are made here

Fig. 6-13

cis face(“receiving” side of Golgi apparatus) Cisternae

trans face(“shipping” side of Golgi apparatus)

TEM of Golgi apparatus

0.1 µm

Fig. 6-16-3

Smooth ER

Nucleus

Rough ER

Plasma membrane

cis Golgi

trans Golgi

Mitochondria

• “powerhouse of cell”= energy is produced

• Site of cellular (aerobic) respiration (ATP is made)

• Was once an independent, free-living organism

Fig. 6-17

Free ribosomesin the mitochondrial matrix

Intermembrane space

Outer membrane

Inner membraneCristae

Matrix

0.1 µm

• More active cells have more mitochondria- WHY?

Ex: muscle cells have more• Has a membrane surrounding And DNA of its own!mtDNA- inherited from

mother/materlineal Used in forensics (sometimes)

Endosymbiont Theory:

Idea that…..

1. Chloroplasts & mitochondria were once free-living

2. Moved into eukaryotic cell

3. Became an organelle of cell

Why do we think this?

Both chloroplasts & mitochondria have:

a) Outer membrane

b) Energy source/function

c) Both have bits of genetic material

Fig. 6-19

1 µm

Chloroplast

Peroxisome

Mitochondrion

Chloroplast

• Plant Cells

• Located in middle of leaf tissue

• Site of photosynthesis

• green- chlorophyll

• Was once free-living, independent• *has maternal DNA (interesting!)

Fig. 6-18

Ribosomes

Thylakoid

Stroma

Granum

Inner and outer membranes

1 µm

Cell Wall

• Plants only

• Support

• Protection

• Made of cellulose: strong carbohydrate

Fig. 6-28

Secondary cell wall

Primary cell wall

Middle lamella

Central vacuoleCytosol

Plasma membrane

Plant cell walls

Plasmodesmata

1 µm

Centrioles

• Animal cells

• Helps move chromosomes apart during mitosis

Cilia and Flagella

• Protein fibers• Cilia- short fibers; all over• Flagella- long fibers; 1 or 2• purpose: locomotion

(movement)• Ex: paramecium, spermatozoa

Fig. 6-23

5 µm

Direction of swimming

(a) Motion of flagella

Direction of organism’s movement

Power stroke Recovery stroke

(b) Motion of cilia15 µm

How Are Plant Cells and Animal Cells Different?

Plants:• Chloroplasts• Cell walls• Central vacuole• Green: chlorophyll• None• Rectangular shape

Animals• None• None• Few, smaller• None• Lysosomes• Different shapes• More mitochondria