Suzanne D'Anna 1

CELLS AND TISSUES

Cell Parts

Suzanne D'Anna 2

Basic Cell defined as the structural and functional unit of all

living things

- as small as 1/1000th of an inch (bacteria)

- as large as 4 feet (certain nerve cells) Shape:

- disc shaped, thread-like, cube-like, etc. Functions:

- protection, hormones, chemical regulation, gas exchange, cleanse blood

Suzanne D'Anna 3

Main Regions of a Cell

plasma (cell) membrane cytosol (cytoplasm) organelles

- specialized highly organized structures for specific cellular activities

inclusions

- temporary structures

Suzanne D'Anna 4

Plasma (cell) Membrane

outer layer of the cell fragile barrier separates internal components of the

cell from the external environment contains cell contents two lipid layers - protein molecules are

suspended between lipid layers

Suzanne D'Anna 5

Plasma (cell) Membrane (cont.)

unique structure which determines which substances enter or leave the cell

Consists of:

- phopholipids

- cholesterol

- proteins

Suzanne D'Anna 6

Functions of Membrane Proteins

channels enzymes transportation of substances across

membrane receptor sites for hormones,

neurotransmitters, or nutrients cytoskeleton anchors cell identity markers

Suzanne D'Anna 7

Cytoplasm

outside nucleus inside plasma membrane site of most cellular activities Major elements include:

- cytosol

- inclusions

- organelles

Suzanne D'Anna 8

Cytosol

viscous, transparent, gel-like 75% H2O + solid components:

- proteins, carbohydrates, lipids, and inorganic substances - inorganic substances and smaller organic substances soluble in H2O are present as solutes - larger organic compounds are

found as colloids (semi-solid matrix)

Suzanne D'Anna 9

Organelles

little organs specialized structures characteristic appearances specific roles in growth, maintenance,

repair, and control chemically different with one another

Suzanne D'Anna 10

Nucleus

Three distinct components:

- nuclear membrane

- nucleoli

- chromatin

Suzanne D'Anna 11

Nucleus (cont.)

largest organelle in the cell usually oval or spherical - conforms to

shape of the cell contains genetic material (DNA) controls cellular functions directs cellular activities surrounded by nuclear membrane

Suzanne D'Anna 12

Nuclear Membrane

double layer bound to nucleus encloses nucleoplasm in which nucleoli

and chromatin are suspended has large pores

Suzanne D'Anna 13

Nucleoli

little nucleus dense body composed mostly of RNA and protein ribosome production (migrate through

pores in nuclear envelope and enter cytoplasm)

disappear during cell division and reappear in daughter cells

Suzanne D'Anna 14

Chromatin

loosely coiled fibers of DNA and associated proteins

before cell division DNA duplicates, chromatin fibers coil and shorten to form chromatids

one of two spiral filaments joined at the centromere which make a chromosome

Suzanne D'Anna 15

Ribosomes

tiny, round dark bodies sites of protein synthesis contain ribosomal RNA (rRNA)

Suzanne D'Anna 16

Endoplasmic Reticulum system of membrane-enclosed tubules

or channels that coil and twist; called cisterns

continuous with nuclear envelope serves as minicirculatory system provides surface area for chemical

reactions Two types:

- granular and agranular

Suzanne D'Anna 17

Endoplasmic ReticulumGranular

rough studded with ribosomes which synthesize

protein temporary storage area together with Golgi body it synthesizes

and packages molecules that will be excreted from the cell

Suzanne D'Anna 18

Endoplasmic ReticulumAgranular (smooth)

site of fatty acid, phospholipid, and steroid synthesis

inactivates or detoxifies chemicals such as alcohol, pesticides, and carcinogens

Suzanne D'Anna 19

Golgi Apparatus (body or complex)

stacks of flattened sacs with bulges at ends

located close to nucleus modifies, packages, and secretes

proteins and lipids as proteins accumulate in sacs, the sacs

swell; swollen sac pinches off to form vesicles that travel to cell membrane

Suzanne D'Anna 20

Route of Proteins for Export

ribosomes rough ER transport

vesicles Golgi body secretory

vesicles release to exterior of cell

Suzanne D'Anna 21

Lysosomes

membrane-enclosed vesicles formed in Golgi body contain powerful digestive enzymes (as

many as 40) responsible for breaking down molecules

can also digest worn-out cell structures (autophagy) and foreign substances

Suzanne D'Anna 22

Peroxisomes

membrane sacs similar to lysosomes but smaller

contain enzymes that use molecular oxygen to oxidize organic substances

detoxify potentially harmful substances that may enter the bloodstream (e.g., free radicals)

especially important in liver and kidneys

Suzanne D'Anna 23

Mitochondria(powerhouse of the cell)

sausage-shaped fluid filled sacs double membrane wall outer wall is smooth inner wall - series of folds called cristae cristae provide surface area for cellular

respiration (only occurs if O2 is present) enzymes on cristae catalyze reactions that

generate ATP

Suzanne D'Anna 24

Cytoskeleton

responsible for cell movement and for movement of organelles and chemicals within the cell

Network of protein structures:

- microfilaments

- microtubules

- intermediate filaments

Suzanne D'Anna 25

Microfilaments

rod-like structures formed from the protein actin in muscle tissue - actin filaments (thin)

and myosin (thick) slide past one another to produce contraction

in non-muscle - actin filaments support and shape

Suzanne D'Anna 26

Microtubules

larger than microfilaments straight, slender cylindrical structures -

contain the protein tubulin support and shape cells movement of substances

Suzanne D'Anna 27

Intermediate Filaments

medium size strong and tough provide structural reinforcement

Suzanne D'Anna 28

Centrosome

cytoplasmic material within centrosome is pair a of rod-shaped

bodies called centrioles

- lie at right angles to each other

- during cell division, centrioles direct formation of mitotic spindle

- like mitochondria, they contain DNA and control self replication

Suzanne D'Anna 29

Cilia

minute projection extending from cell surface

contain ten pairs of microtubules act to move substances along cell surface beat rhythmically to move fluids or

particles over cell surface

Suzanne D'Anna 30

Flagella

long whip-like projections extending from free cell surface

act to propel a cell contain ten pairs of microtubules tail of sperm is a flagellum