Cells

Cells

The 3 Basic Parts of all Cells

1. Plasma Membrane• Controls what enters & exits the cell

2. Cytoplasm• Entire contents of cell between P.M.

and nucleus • Where most metabolic activity occurs

3. Nucleus or Nuclear Area• Contains DNA, the genetic material

– Phospholipids form a two-layer sheet• Called a phospholipid bilayer, with the heads facing

outward and the tails facing inward

Figure 5.11B

Water

Water

Hydrophilicheads

Hydrophobictails

Classes of Cells• Two basic types of cells:

1. Prokaryotic cells2. Eukaryotic cells

Prokaryotic cells are structurally simpler than eukar yotic cells

Prokaryotic cellNucleoidregion

Nucleus

Eukaryotic cell Organelles

Col

oriz

ed T

EM

15,

000

Figure 4.3A

Prokaryotic Cell

Nuclear area

Pili

Flagella

Ribosomes

Cell wall

Plasma membrane

Figure 4.3B

Eukaryotic cells Animal Cell

Fig 4.4A

1. The nucleus is the cellular control center• Containing the cell’s DNA, which directs cellular

activities

NucleusChromatin

Nucleolus

Pore

Ribosomes

Roughendoplasmicreticulum

Two membranesof nuclearenvelope

Figure 4.5

2. Smooth endoplasmic reticulum, or smooth ER • Synthesizes lipids • Processes toxins and drugs in liver cells• Stores and releases calcium ions in muscle

cells Smooth ER

Rough ER

Nuclearenvelope

Rough ERRibosomes

Smooth ER

TEM

45,

000

Figure 4.7

3. Rough endoplasmic reticulum or Rough ER– Ribosomes on the surface

• Produce proteins that are secreted, inserted into membranes, or transported in vesicles to other organelles

Secretory(glyco-) proteininside trans-port vesicle

4Transport vesiclebuds off

Sugar chain3

Rough ER

Glycoprotein2Polypeptide

Ribosome

1

Figure 4.8

4. The Golgi apparatus finishes, sorts, and ships cell products– Stacks of membranous sacs receive and modify ER

products then ship them to other organelles or the cell surface

Figure 4.9Golgi apparatus

TEM

130

,000

Transportvesicle fromthe Golgi“Shipping” side

of Golgi apparatus

Golgiapparatus

“Receiving” side ofGolgi apparatus

Transportvesiclefrom ER

New vesicleforming

5. Vesicles: – Membrane-bound “balloons” that transport and

store substances in cells

6. Lysosomes are sacs of enzymes

• function in digestion within a cell

• Lysosomes in white blood cells destroy bacteria that have been ingested

• recycle damaged organelles

Fig 4.13

•The various organelles of the endo-membrane system are inter-connected structurally and functionally

7. Mitochondria harvest chemical energy from food– Mitochondria carry out cellular respiration which

uses the chemical energy in food to make ATP for cellular work

Figure 4.14

Mitochondrion

Outermembrane

Intermembranespace

Matrix

Innermembrane

Cristae

TEM

44,

880

8. Cytoskeleton & related structures - • a network of protein fibers • help organize its structure and activities

Actin subunit

Microfilament

7 nm

Fibrous subunits

10 nm

Intermediate filament Microtubule

25 nm

Tubulin subunit

Fig 4.17

– Microfilaments of actin • Enable cells to change shape and move

– Intermediate filaments • Reinforce the cell and anchor certain organelles

– Microtubules give the cell rigidity• And provide anchors for organelles and act as tracks for

organelle movement

Cilia and flagella move when microtubules bend– Eukaryotic cilia and flagella are locomotor appendages

that protrude from cer tain cells

LM 6

00

Col

oriz

ed S

EM

4,1

00

Figure 4.18

– Tight junctions • can bind cells together into leakproof sheets

– Anchoring junctions • link animal cells into strong tissues

– Gap junctions • allow substances to flow from cell to cell

Anchoring junction

Tight junctions

Gap junctions

Extracellular matrix

Space between cells

Plasma membranes of adjacent cells

Figure 4.18B

http://learn.genetics.utah.edu/content/begin/cells/scale/

http://learn.genetics.utah.edu/content/begin/cells/insideacell/

Please do the activities at the following 2 sites:

Plant Cell –Fig. 4.6b

Plant cells also have:1. Vacuole

• stores water, solutes, waste• Important for growth and rigidity

2. Chloroplasts• Site of photosynthesis: conversion of light to

ATP which drives formation of sugars3. Cell wall

• Protects, supports**Plant cells do not have lysosomes

Vacuoles function in the general maintenance of the cell– lysosomal and storage functions

Chloroplast

Centralvacuole

NucleusC

olor

ized

TE

M 8

,700

Figure 4.12

Chloroplasts convert solar energy to chemical energy– found in plants and some protists – convert solar energy to chemical energy in sugars

TEM

9,7

50

Chloroplast

Stroma

Intermembranespace

Inner and outermembranes

Granum

Figure 4.15

Plant cells • have rigid cell walls made of cellulose• Are connected by plasmodesmata - connecting

channels

Plasma membrane

Cytoplasm

Plasmodesmata

Vacuole

Layers of one plant cell wall

Walls of two adjacent plant cells

Figure 4.22