Chapter 7: Inside the Cell

External structures enable movement and attachment

-Motor embedded in plasma membrane

Endosymbiosis

A number of characteristics of eukaryotic organelles are evidence that some organelles were once free living prokaryotic cells Mitochondria and chloroplasts Cirular DNA/non-histone proteins Binary fission 70s ribosomes Double Membrane structure

Prokaryotic and Eukaryotic Cells

All cells are surrounded by a plasma membrane. The semifluid substance within the membrane is the cytosol, containing the organelles. All cells contain chromosomes that have genes in the form of DNA. All cells also have ribosomes, tiny organelles that make proteins using the instructions contained in genes.

Phylogentically, we have three domains of life

Bacteria Archaea Eukarya

Bacteria

Bacterial cells are highly organized, with an array of distinctive structures found among millions of species. Bacterial membranes consist of fatty acids bound to glycerol Prokaryotic DNA (supercoiled)

Cilia and flagella

Cilia and flagella, common locomotary appendages of cells, are made of microtubules. Flagella are typically longer than cilia, and cells that have them usually have only one or two. Cilia are shorter and usually present in great numbers.

Eukaryotic Cells (protists, fungi, plants, and animals) are compartmentalized by membrane-bound organelles

Compartmentalization offers two key advantages Incompatible chemical reactions can be separated. Chemical reactions can become more efficient.

Golgi Apparatus

Consists of stacks of membraneous sacs These receive and modify ER products, then send them on to other organelles or to the cell membrane Organelle structure composed of stack line containers called cysterny Function: to receive material from the ER, modify, sort, package, and send to other organelles or cell membrane

Eukaryotic and Prokaryotic Cells

Eukaryotic cells and many prokaryotic cells may be embedded in an extracellular matrix It is a sticky layer of glycoproteins It binds cells together in tissues/biofilms It can also have protective and supportive functions Analogy: Bone/skeleton in humans is extracellular matrix

Prokaryotic versus eukaryotic cells (star)

Eukaryotic cells are usually larger than prokaryotic cells. Eukaryotic chromosomes are inside a membrane-bound nucleus. Eukaryotic cells have a larger number of distinct organelles. Embedded in an extracellular matrix Sticky layer of proteins Binds cells together in tissues/biofilms Can also have protective + supportive functions

Vacuoles

Function in the general maintenance of the cells Plant cells contain a large central vacuole The vacuole has lysosomal and storage functions Store carbohydrates

dynein

In both cilia and flagella, the microtubules are cross-linked by spokes of the motor protein called dynein. Dynein changes its shape when energy is released from ATP. Many dynein molecules associate along the length of the microtubule pair. Dynein moves vesicles toward the minus end of the microtubule. Kinesin, another motor protein, moves them toward the plus end.

Nucleus (Eukaryotic)

Information storage and processing The nucleus is the largest organelle in the cell. It is enclosed by a double membrane called the nuclear envelope. It has a nuclear envelope supported by the nuclear lamina. (stiffens membrane) It contains the genetic information of the cell, DNA. (chromosomes) It contains the nucleolus (specialized structure of the nucleus), the site of rRNA synthesis and ribosome (subunit) assembly.

Eukaryotic Cell Surfaces and Junctions

Junctions is when two cells meet each other Cell surfaces protect, support, and join cells Cells interact with their environments and each other via their surfaces Plant cells are supported by rigid cell walls made largely of cellulose They connect by plasmodesmata (passageway), channels that allow them to share water, food, and chemical messages Cytoplasm of one cell is connected to cytoplasm of another cell

Rough ER

Makes membrane and proteins Attaches ribosome to surface Manufactures membranes Ribosomes on its surface produce proteins

Protists

May have contractile vacuoles

Microfilaments

Microfilaments are made of the protein actin, and may exist as single filaments, in bundles, or in networks. Microfilaments are needed for cell contraction, as in muscle cells, and add structure to the plasma membrane and shape to cells. They are involved in cytoplasmic streaming, and the formation of pseudopodia. Those composed of actin enable cells to change shape and move

Three types of cytoskeletal components

Microfilaments, intermediate filamens, and microtubules

Functions of the Golgi apparatus (eukaryotic) (star)

Modifies products of the ER Lipid production - sphingolipids, glycolipids Carbohydrate additions - O-linked glycoproteins Manufactures certain macromolecules Sorts and packages materials into transport vesicles

The cytoskeleton

Motor proteins move along microtubules and microfilaments. Myosins are associated with movement on actin filaments

Components of endomembrane system

Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane *These components are either continuous or connected via transfer by vesicles carried by motor proteins

Plasmodesmata

Passage way through cell wall structure so material from one cell cytoplasm can move to another cell cytoplasm

Chloroplasts

Photosynthesis Converts solar energy to chemical energy Found in plants and some protists Convert solar energy to chemical energy in sugars(organic molecules)

Ribosomes (Eukaryotic)

Ribosomes are found in the cytosol. (not surrounded by membrane not organelle) They are molecular machines that synthesize proteins. Site of protein synthesis, associated with ER

Peroxisomes

Single membrane, vesicles from ER Peroxisomes are centers for oxidation reactions. They generate hydrogen peroxide as a by-product of these reactions. They contain an enzyme, catalase, which converts hydrogen peroxide into water and oxygen. Plants have special peroxisomes, called glyoxosomes, which convert the products of photosynthesis into a storable sugar. (energy)

There are two distinct regions of ER:

Smooth ER, which lacks ribosomes Rough ER, with ribosomes studding its surface

The Golgi Apparatus (eukaryotic) (star)

The Golgi apparatus consists of flattened membranous sacs called cisternae --flattened membrane bound compartments It has polarity: a cis (vesicle) side that receives proteins from the rough ER, and a trans side that ships proteins to their final destination.

Many Organelles are related through the endomembrane system

The endomembrane system is a collection of membraneous organelles -These organelles manufacture and distribute cell products -The endomembrane system divides the cell into compartments (2 aqueous solutions) -ER is a part of the endomembrane system

endomembrane system

The endomembrane system regulates protein traffic and performs metabolic functions in the cell

cytoskeleton

The microtubules in cilia and flagella are arranged in a 9 + 2 array. At the base of each flagellum or cilium is a basal body. The nine pairs extend into the basal body. Centrioles are found in an organizing center near the cell nucleus. Centrioles are similar to basal bodies, but are located in the center of the cell and help in the movement of chromosomes during cell division.

Organelles of the Endomembrane System

The nucleus is the cell's genetic control center The largest organelle is usually the nucleus Double membrane The nucleus is separated from the cytoplasm by the nuclear envelope(double membrane) nucleoplasm- Interior. Cytoplasm-exterior Nucleus is the cellular control center (refer to transcription/translation)

Endomembrane system

The various organelles of the endomembrane system are interconnected structurally and functionally

The Cell wall (Prokaryotic) forms a protective exoskeleton

Tough fibrous layer surrounds the plasma membrane, giving it shape and rigidity. Molecularly bacterial cell walls contain peptidoglycan while Archaeal walls do not.

Vacuoles in Plants and Fungi (Eukaryotic)

Vacuoles occupy most of the volume of plant cells. They act as a storage depot for water, ions, and sometimes proteins. They may contain noxious substances that protect the plant from predators. Digestive enzymes, recycling centers, and large storage containers

Abnormal Lysosomes

can cause fatal diseases Lysosomal storage diseases are hereditary They interfere with other cellular functions Tay-Sachs disease

Microtubules can:

give the cell rigidity provide anchors for organelles act as tracks for organelle movement

Smooth ER

has a variety of functions Synthesizes lipids W/o ribosomes, Smooth Regulates carbohydrate metabolism and breaks down toxins and drugs Carries out enzymatic activities to manufacture lipids for the cell (phospholipids and steroids)

Microtubules

hollow cylinders made from tubulin protein subunits. Microtubules provide a rigid intracellular skeleton for some cells, and they function as tracks that motor proteins can move along in the cell. They regularly form and disassemble as the needs of the cell change.

Smooth ER (star)

synthesizes lipids (enzymes) Metabolizes carbohydrates Detoxifies poison Stores Calcium ions

Lysosomes: Digestive Compartments (eukaryotic) (star)

A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acid, exported via transport protein. Lysosomes are involved in solid-waste processing and material storage. (recycling center) Lysosomes have a proton pump in their membrane that keeps the lumen acidic. They contain digestive enzymes, called acid hydrolases, that work best in acidic conditions to hydrolyze macromolecules. Golgi/ER/Lysosomes jointly form the endomembrane system. The endomembrane system is for producing, processing, and transporting proteins and lipids in eukaryotic cells.

cell theory

All cells derived from preexisting cells. All life forms contain the following characteristics: Proteins Nucleic Acids: Hereditary molecules Carbohydrates Plasma membrane: separates different environmental conditions Schleiden, Schwann, Hooke, and Virchow Observations: cells are the basic unit of life and living things are composed of cells

Archaea

Archaeal membranes consist of isoprenoid chains bound to glycerol, making it more stable for extreme environments Molecularly bacterial cell walls contain peptidoglycan while Archaeal walls do not.

Lysozomes

Digest the cell's food and wastes Sacs of digestive enzymes budded off the Golgi

Cilia and Flagella move when microtubules bend

Eukaryotic cilia and flagella are locomotor appendages that protude from certain cells A cilia or flagellium is composed in an extension of the plasma membrane Surrounded by plasma membrane Protein internal structure (microtubule) Flagella is just larger

Mitochondria

Harvest chemical energy from food Mitochondria carry out cellular respiration This process uses the chemical energy in food to make ATP for cellular work

Rough ER (star)

Has bound ribosomes which produce secreted, integral or exterior membrane-anchored proteins Has bound ribosomes which produce proteins utilized in lysosomes Produces glycoproteins (proteins covalently bonded to carbohydrates, N-linked) Distributes transport vesicles, proteins surrounded by membranes transported by motor proteins. Is a membrane factory for the cell The rough ER has ribosomes bound to the cytoplasmic surface on which secreted and transmembrane proteins are made. It contains enzymes in the lumen (packages into vesicles) that fold and modify proteins after they are synthesized on bound ribosomes.

Eukaryotic Cells

In a eukaryotic cell, chromosomes are contained in a membrane-enclosed organelle, the nucleus. The region between the nucleus and the plasma membrane is the cytoplasm In eukaryote cells, the chromosomes are contained within a membranous nuclear envelope. Within the cytoplasm of a eukaryotic cell are a variety of membrane-bound organelles of specialized form and function. Eukaryotic cells are generally much bigger than prokaryotic cells.

Prokaryotic Cells

In a prokaryotic cell, the DNA is concentrated in the nucleoid without a membrane separating it from the rest of the cell All the material within the plasma membrane of a prokaryotic cell is cytoplasm. These membrane-bound organelles are absent in prokaryotes.

Nucleus

Nucleus is the largest and most important cellular organelle in an eukaryotic cell. Usually it is spherical or oval in shape and is placed in the centre of the cell. Nucleus generally consists of the nuclear membrane, nucleoplasm, chromatin material, and the nucleolus.

nucleoid

Nucleoid is mainly found in Prokaryotes such as bacteria and blue-green algae. It is an undefined nuclear region containing only nucleic acids. Generally it contains single circular chromosome, which stores genetic information of prokaryotes. There is no nuclear membrane and other organized nuclear regions in nucleoid when compared to nucleus. Due to lack of surrounding membranes, this is not separated from the remainder of the prokaryotic cytoplasm

Mitochondria (eukaryotic)

Organelle surrounded by 2 membranes Mitochondria are the sites of ATP synthesis. -Harvest chemical energy from food, carry out cellular respiration, uses chemical energy in food to make ATP for cellular work They have two membranes: -The outer membrane is smooth. -The inner membrane contains folds called cristae. (location of electorn transport chain and ATP synthase) -The mitochondrial matrix is inside the inner membrane. Mitochondria contain some of their own DNA, mitochondrial DNA (mtDNA). They make their own ribosomes: encode RNA for mitochondrial ribosomes, produce mitochondrial proteins They can divide independently of cell division.

Organelles (Prokaryotic)

Organelles perform specialized functions Contain enzymes/structures specialized for a particular function Recent research indicates the presence of internal compartments in bacteria that qualify as organelles Many organelles have embranes, and have specialized tasks related to the storage of ions (ca), enzymes, and minerals Organizes enzymes responsible for synthesizing complex carbon compounds from CO2 Organelles hold crystals of magnetite, function like a compass needle to help cells swim in a directed way

The Plasma Membrane (prokaryotic)

Phospholipid bilayer Separates life from nonlife Control's cells contact with environment Cytoplasm: contents of a cell bounded by plasma membrane Bacterial membranes consist of fatty acids bounded to glycerol Archaeal membranes consist of isoprenoid chains bound to a glycerol, making it more stable for extreme environments, which are inhabited by certain species within its domain

Photosynthesis (Prokaryotic)

Photosynthetic species have internla membrane complexes

Primary differences (Prokaryotic and Eukaryotic Cells)

Prokaryotic cells (bacteria and archaea) differ from eukaryotic cells in a number of features of structure and function

Prokaryotic cell components

Ribosome, Chromosome, cytoskeleton, plasma membrane, cell wall

Phagocytosis + Lysosomes

Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell's own organelles and macromolecules, a process called autophagy

The Cytoskeleton (prokaryotic)

Structures the cell interior Current research reveals a more complex cytoskeletal network with protein fibers and filaments that aid in cell division and cell shape.

The cytoskeleton (protein structure)

Supports structure The cell's internal skeleton helps organize its structure and activities A network of protein fibers makes up the cytoskeleton

Plasmid (extra-chromosomal DNA) and Chromsome

The chromosome is organized in a nucleoid: contains DNA and proteins. Bacterial DNA is inside a chromosome, which contains Genes. In order to fit within the nucleoid, the chromosome is supercoiled (plasmid, which is a supercoiled DNA molecule) Some bacterial cells have additional DNA molecules called plasmids that carry genes which help cells adapt to unusual circumstances. Plasmids are small, supercoiled DNA molecles independent of cell's main chromosome in prokaryotes and some Eukaryotes Chromosomes are single , long molecule of double stranded DNA and associated proteins.

The Endoplasmic Reticulum (Star)

The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope Network of membrane-bound sacs and tubules Smooth ER + Rough ER

Residual Materials of Digestion

The materials that result from lysosomal digestion are processed in multiple ways. Exocytosis of waste materials Uptake into cytoplasm of subunits (monomers) Recycling of lysosomal enzymes Presentation of peptide components on cell surface (immunological signalling)

Intermediate filaments

are found only in multicellular organisms, forming ropelike assemblages in cells. They have two major structural functions: to stabilize the cell structure, and resist tension. In some cells, intermediate filaments maintain the positions of the nucleus and other organelles in the cell.

Ribosome (prokaryotes)---Macromolecular machine

composed of large and small subunits Synthesizes protein by using the genetic information encoded in mRNA Ribosome size and function in bacteria and archea are similar, but the primary structures of RNA and protein differ. 2 subunits; each coposed of Ribosomal RNA and proteins

Lysosomal Enzymes

digest food destroy bacteria recycle damaged organelles function in embryonic development in animals

The Cytoskeleton

maintains cell shape and support. provides the mechanisms for cell movement. acts as tracks for "motor proteins" that help move materials within cells.