BIOLOGY 1111

Chapter 4

Northland Community & Technical College

Instructor Terry Wiseth 

CELL THEORY

smallest entity that retains the characteristics of life

1) complex organization

2) metabolic activity

3) reproduction 

GENERALIZATIONS OF CELL THEORY

1) all organisms are composed of cells

2) cells are the basic unit of life

3) new cells arise only from cells that already exist 

CELL SIZE

most cannot be seen without the aid of a microscope

larger cells

”yolk” of bird eggs

fish eggs “caviar” 

human eyes have a resolution of about 100 microns 

LIGHT MICROSCOPE

The light microscope has a limit of resolution of about 200 nm (0.2 microns) 

TEM

The Transmission Electron Microscope (TEM) has a limit of resolution of about 2 nm 

SEM

The Scanning Electron Microscope (SEM) also has a limit of 2 nm 

CELL SIZE

cell size dictated by surface area-to-volume ratio

an object’s volume increases with the cube of the diameter

surface area increases with the square of the diameter 

as diameter increases, volume increases more rapidly than its surface area does

membrane surface area is not sufficient to supply the cytoplasm volume 

TWO TYPES OF CELLS 

EUKARYOTIC CELLS

1) contains distinctive internal organelles

2) contains nucleus which houses DNA 

PROKARYOTIC CELLS

1) lack a nucleus

2) bacteria are the only prokaryotic cells 

PROKARYOTIC CELLS

1) all bacteria are prokaryotic

2) smallest and simplest of cells

3) many have flagella for locomotion

4) rigid cell wall surrounds the cell membrane supports the shape of the cell

5) irregular shaped DNA region DNA is in ring shape

6) bacteria are metabolically diverse 

EUKARYOTIC CELLS

1) more complex cells

2) contain a nucleus with DNA and organelles

3) contain cytoplasm surrounded by a plasma membrane

4) some cells have a cell wall in addition to a plasma membrane plants, fungi 

GENERALIZATIONS OF CELL THEORY

cells vary in size, shape and activities

all cells have:

1)  Plasma membrane

2)  DNA region

3)  Cytoplasm

4)  Organelles 

PLASMA MEMBRANE

outer membrane maintains the integrity of the cell

membrane does not however isolate the cell

Cell membrane

“lipid bilayer”

boundary that bars free passage of water soluble substances in and out of the cell

Embedded proteins

carry out membrane functions 

MEMBRANE PROTEINS

types of membrane proteins

1)  Passive channels

2)  Protein pumps

3)  Protein receptors

4)  Recognition proteins

5)  Adhesive proteins 

NUCLEUS

DNA is localized in the cell nucleus 

CYTOPLASM

everything enclosed by the plasma membrane except the DNA semi-fluid 

ORGANELLES

organelles--internal sacs which have a specific metabolic function

essential in keeping chemical reactions in the cytoplasm separate from each other types of organelles may be different plant and animal cells 

NUCLEUS

nucleus sequesters DNA

1)  separates DNA from chemical reactions in cytoplasm

2)  nuclear membranes control access between nuclear material and cytoplasm 

Nuclear envelope has pores to allow passage of messenger units of nucleic acid 

NUCLEOLUS

1) assembly of RNA and ribosomes

2) storage of RNA and ribosomes 

NUCLEUS

instructions for building proteins (enzymes) are contained in DNA

instructions of heredity are distributed in several DNA molecules of various lengths

humans = 46 DNA molecules 

CHROMOSOMES

DNA is threadlike

prior to cell division the DNA molecules duplicate

DNA folds and twists into condensed structures called chromosomes 

CYTOMEMBRANE SYSTEM

Series of organelles through which lipids and proteins, produced on cytoplasmic ribosomes, pass through in becoming packaged for export

 1)  Endoplasmic reticulum (ER)

2)  Golgi bodies

3)  Lysosomes

4)  Vesicles 

ENDOPLASMIC RETICULUM

1)  Rough endoplasmic reticulum ribbon like structure with ribosomes attached

arranged as flat, stacked sacs 

RIBOSOMES

ribosomes are small spherical shaped structures

serve as the “working table” for assembling proteins 

ENDOPLASMIC RETICULUM

2)  Smooth endoplasmic reticulum lacks ribosomes

appears like a system of pipes

    A)  lipid synthesis

        ex:  seeds--produce steroid hormones

    B)  inactivate harmful by-products of metabolism and drugs

        ex:  liver cells 

GOLGI BODIES

Resemble stacks of pancakes

flattened sacs in which lipids and protein molecules are modified

modifications allow for sorting and packaging for transport 

VESICLES

Sacs which transport or store enzymes, lipids and proteins

1)  Peroxisomes

2)  Glyoxysomes

3)  Lysosomes  (microbodies)   

PEROXISOMES

contain enzymes to break down fatty acids and amino acids 

result is the release of hydrogen peroxide

requires catylase to convert hydrogen peroxide to water and oxygen

    ex:  liver cells degrade alcohol 

GLYOXYSOMES

vesicles in plant cells with enzymes to convert stored fats and oils to sugars

    ex:  newly germinated seeds 

LYSOSOMES

vesicles of intracellular digestion

contain enzymes which can break down any polysaccharide, protein, nucleic acid and some lipids   

TAY-SACHS DISEASE

Lysosomal storage disease

lipids accumulate in lysosomes because they cannot be broken down

important in proper function of blood cells (immunity)

Lysosomes play an important role in aptosis important in cell reclamation (tadpole tail) 

CYTOMEMBRANE SYSTEM

raw materials (amino acids and lipids) are dissolved in the cytoplasm under the instructions of the DNA molecule

polypeptide chains of proteins are assembled from the dissolved raw materials

1)  DNA instructions leave the nucleus

2)  protein chains are assembled on ribosomes

3)  chains enter the Rough ER

4)  lipids are formed in the Smooth ER

5)  vesicles (containing lipids and proteins) bud from the rough and smooth ER membranes and transported to the Golgi bodies

6)  proteins and lipids take on final form in Golgi bodies

7)  Vesicles bud from the Golgi bodies with the finished product

8)  products are transported by vesicles to the cell membrane and released by exocytosis 

MITOCHONDRIA

contains a series of inner membranes folded repeatedly (cristae)

increases the total surface area available for reactions

use oxygen to assist in liberating energy stored in sugars

energy is used to form ATP molecules

ATP-molecule is able to store and transport energy for short periods of time

most numerous in high energy demanding cells

    ex:  muscles, liver

may have evolved from engulfed bacteria which escaped digestion

contains its own DNA and is able to divide

All your mitochondria come from your mother 

SPECIALIZED PLANT ORGANELLES

Plastids

1) Chloroplast  

2) Chromoplast                             

3) Amyloplasts 

CHLOROPLASTS

organelles of photosynthesis

a) light energy absorbed

b) ATP formed

c) organic compounds synthesized 

oval, disk shaped

internal disk shaped compartments are stacked together  (grana)

light energy trapped by pigments and converted to ATP energy in the grana

sugars and starch are synthesized in the fluid outside of the grana

starch may also be temporarily stored in the fluid

may also have evolved from bacteria engulfed but not digested

chlorophyll  (a green pigment)  and carotenoid pigments are able to capture light energy 

CHROMOPLASTS

lack chlorophyll but have carotenoids

carotenoids = yellow, orange, red pigments 

AMYLOPLASTS

lack any pigments

store starch

abundant in stems, potato tubers and seeds 

CENTRAL VACOULE

occupies 50% - 90% of the cell interior

stores amino acids, sugars, ions and wastes

serves to increase the cell surface area 

CYTOSKELETON

interconnected system of bundled fibers, threads and lattices

extend from the cell membranes, organelles and nucleus

supply internal organization, shape, ability to move, reinforce the cell membrane and hold proteins in place

cytoskeleton consists of microtubles and microfilaments which are assembled from proteins

    ex:  muscle cells - filaments for contraction

    ex:  amoeboid movement - Amoeba, white blood cells

    ex:  cilia action - nasal passages, Paramecium

    ex:  flagella - sperm cells, Euglena

    ex:  centrioles - important in cell division

    ex:  molecular motors – cell organelle movement

CELL SURFACE SPECIALIZATIONS 

Cell Wall

bundles of cellulose strands form around plasma membrane

Pectin

    deposits make cell wall rigid

Plasmodesmata

    interconnecting tubes and channels between cells which allow exchanges of cytoplasm in plant cells

Gap Junctions

    channels of exchange in animal cells

    ex:  liver, heart

Junction Proteins

    hold cells together in forming tissues 

EXOCYTOSIS

A process of transporting materials out of the cell cytoplasm

1) waste products

    vacuoles

2) excess water

    contractile vacuoles

3) hormones

    insulin, testosterone, etc

4) neurotransmitters

    nerve cells 

ENDOCYTOSIS

A process of bringing materials into the cell cytoplasm from outside the membrane

    Pinocytosis

bringing water into the cell

intestinal cells

    Phagocytosis

bringing solid material into the cell

white blood cells

amoeba 

END 

CHAPTER 4