Cell Structure and Function Quiz

• Cells are structural units of all living things
• The human body has between 50 and 100 Trillion cells

Cellular Basis of Life: Cell Theory

• The cell is the basic structural and functional unit of living organisms
• How an organism functions depends on the collective activities of its cells
• Cells cooperate to form tissues, tissues form organs, and organs perform specific functions
• The principle of complementarity states that the biochemical activities of cells are dictated by their structure (anatomy), which determines their function (physiology)
• Continuity of life has a cellular basis
• Apoptosis- programmed cell death occurs naturally
• Necrosis- cell death due to stimuli

Composition of Cells

• Carbon is approximately 11% of a cell
• Hydrogen is approximately 59% of a cell
• Oxygen is approximately 24% of a cell
• Nitrogen is approximately 3-4% of a cell
• Cells are about 60-80% water

The Nucleus

• The nucleus is located in the middle of the cell and acts as its control center
• It contains DNA, also known as deoxyribonucleic acid
• DNA is needed for building proteins and is necessary for cell reproduction
• The nuclear envelope, a double membrane, binds the nucleus
• Nuclear pores in the envelope allow for the exchange of material with the rest of the cell
• Nucleoplasm is the jellylike fluid enclosed by the nuclear envelope
• The Nucleolus contains one or more dark-staining nucleoli and is the site of ribosome assembly
• Ribosomes migrate into the cytoplasm through nuclear pores to perform protein synthesis
• Chromatin is composed of DNA wound around histones (proteins)
• Scattered throughout the nucleus & present when the cell is not dividing
• Chromosomes are formed when the cell divides

Plasma Membrane

• Transparent barrier for cell contents
• Contains and separated cell contents from surrounding environment

Role of Proteins

• Specialized membrane functions are the responsibility of proteins
• Enzymes, receptors for hormones, chemical messengers, channels, and carriers

Fluid Mosaic Model

• Two layers of phospholipids arranged tail to tail
• Cholesterol and proteins are scattered among the phospholipids
• Sugar groups may be attached to the phospholipids forming glycolipids
• Phospholipids are polar molecules; the charged end interacts with water, while the fatty acid chains do not
• This polarity makes phospholipids a good foundation for cell membranes

Phospholipid Arrangement

• Hydrophilic (water-loving) polar heads are oriented on the inner and outer surfaces of the membrane
• Hydrophobic (water-fearing) nonpolar tails form the center (interior) of the membrane
• This makes the plasma membrane relatively impermeable to most water-soluble molecules

Role of Sugars

• Glycoproteins are branched sugars attached to proteins that abut the extracellular space
• Glycocalyx is the fuzzy, sticky, sugar-rich area on the cell's surface

Cell Membrane Junctions

• Cells are bound together in three ways
• Glycoproteins in the glycocalyx act as an adhesive or cellular glue
• Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion
• Special cell membrane junctions are formed, which vary structurally depending on their roles

Main Types of Junctions

• Tight junctions are impermeable and bind cells together into leakproof sheets
• Plasma membranes fuse like a zipper to prevent substances from passing through extracellular space between cells
• Desmosomes are anchoring junctions, like rivets, that prevent cells from being pulled apart as a result of mechanical stress
• They are created by buttonlike thickenings of adjacent plasma membranes
• Gap junctions are communicating junctions that allow communication between cells
• Hollow cylinders of proteins (connexons) span the width of the abutting membranes
• Molecules can travel directly from one cell to the next through these channels

The Cytoplasm

• The cellular material outside the nucleus and inside the plasma membrane
• Site of most cellular activities
• Includes cytosol, inclusions, and organelles

Three Major Components of Cytoplasm

• Cytosol is the fluid that suspends other elements and contains nutrients and electrolytes
• Inclusions are chemical substances, such as stored nutrients or cell products, that float in the cytosol
• Organelles are metabolic machinery of the cell that perform functions for the cell

Cell Physiology

• Cells have the ability to:
  • Metabolize
  • Digest Food
  • Dispose of Wastes
  • Reproduce
  • Grow
  • Move
  • Respond to Stimulus

Organelles: Structure and Function

Plasma Membrane

• Structure: Membrane made of a double layer of lipids (phospholipids, cholesterol, etc.) with proteins embedded within; some externally facing proteins and lipids have sugar groups attached
• Functions: Cell barrier; acts in the transport of substances into or out of the cell. Maintains an electrical condition that essential for functioning excitable cells

Cytoplasm

• Structure: Cellular region between the nuclear and plasma membranes. Consists of fluid cytosol containing dissolved solutes, organelles (the metabolic machinery of the cytoplasm), and inclusions (stored nutrients, secretory products, pigment granules)

Mitochondria

• Structure: Rodlike, double-memebrane structures; inner membrane folded into projections called cristae
• Function: Site of aerobic respirtation and ATP synthesis; powerhouse of cell

Ribosomes

• Structure: Dense particles consisting of two subunits, each composed of ribosomal RNA and protein; free or attached to rough endoplasmic reticulum
• Function: The sites of protein synthesis

Rough Endoplasmic Reticulum

• Structure: Membranous system enclosing a cavity, the cistern, and coiling though the cytoplasm externally studded with ribosomes.
• Function: Sugar groups are attached to protein tunnels; the proteins are bound in vesicles for the transports to the Golgi apparatus and other sites; in general these synthesize both protein and phospholipids

Smooth Endoplasmic Reticulum

• Structure: Membranous system of tubules and sacs; free of ribosomes
• Functions: Site of lipid and steroid (cholesterol) synthesis, lipid metabolism, and drug detoxification

Golgi Apparatus

• Structure: Stack of flattened membranes and associated vesicles close to the ER
• Functions: Packages, modifies, and segregates proteins for secretion from the cell, inclusion in lysosomes or Incorporation into the plasma membrane

Peroxisomes

• Structure: Membranous sacs of oxidase and catalase enzymes.
• Functions: The enzymes detoxify a number of toxic substances such as free radicals

Lysosomes

• Structure: Membranous sacs containing acid hydrolases
• Functions: Sites of intracellular digestion

Microtubules

• Structure: Cylindrical structures made of tubulin proteins
• Functions: Support the cell and give it shape, Involved in intercellular and cellular movements; form centrioles and cilia and flagella

Microfilaments

• Structure: Fine filaments composed of Protein actin
• Functions: Involved in muscle contraction and other types of intracellular filaments

Intermediate Filaments

• Structure: Protein fibers, composition varies.
• Functions: The stable cytoskeletal elements; resist mechanical forces acting on the cell

Centrioles

• Structure: Paired cylindrical bodies, each composed of nine triplets of microtubules
• Functions: Organize a microtubule network during mitosis (cell division) to form the spindle and asters. Form the bases of cilia and flagella

Inclusions

• Structure: Varied; includes stored. Nutrients such as lipid droplets and glycogen granules, protein crystals, pigment granules
• Functions: Storage for nutrients, wastes, and cell products

Nucleus

• Structure: Largest organelle. Surrounded by the nuclear envelope; contains fluid nucleoplasm, nucleoli, and chromatin.
• Functions: Control center of the cell: responsible for transmitting genetic information and providing the instructions for protein synthesis

Nuclear Envelope

• Structure: Double-membrane structure pierced by large pores. Outer membrane continuous with the endoplasmic reticulum.
• Function: Separates the nucleoplasm from the cytoplasm and regulates passage of substances to and from the nucleus

Nucleolus

• Structure: Dense spherical (non-membrane-bounded) bodies, composed of ribosomal RNA proteins.
• Function: Site of ribosome subunit manufacture

Chromatin

• Structure: Granular, threadlike material composed of DNA and histone proteins. "Beads on a string."
• Functions: DNA constitutes the genes, which carry instructions for building proteins

Cell Extensions

• Surface extensions found in some cells, also known as accessories

Cilia:

• Move materials across the cell surface
• Located in the respiratory system to move mucus

Flagella

• Propels the cell; the only flagellated cell in the human body is the sperm

Microvilli

• Tiny, fingerlike extensions of the plasma membrane; increase surface area for absorption and smaller than cilia

Cell Diversity

• The human body houses over 200 different cell types
• Cells vary in size, shape, and function
• Cells vary in length from 1/12,000 of an inch to over 1 yard (nerve cells)
• Cell shape reflects its specialized function

Cell That Connect Body Parts

• Fibroblast: Secret cable-like fibers, used in wound healing and usually seen on the skin
• Erythrocyte (RBC): Bi-concave disks that carry oxygen in the bloodstream

Cells that Cover and Line Body Organs

• Epithelial cells: Packs together in sheets, intermediate fibers resist tearing, and lining of organs

Cells that Move Organs and Body Parts

• Skeletal and smooth muscle cells have contractile filaments and allow cells to shorten forcefully
• The heart has cardiac muscle cells

Cells that Store Nutrients

• Fat Cells: store lipid droplets in the cytoplasm and provide insulation and thermal regulation

Cells that Fight Diseases

• Macrophage: also known as white-blood cells, digests infectious microorganisms

Cells that Gather Information

• Nerve cells/neurons receive and transmit messages to other body structures

Cells of Reproduction

• Oocyte: Largest cell in the body; divides to become and embryo upon fertilization Sperm: Built for swimming to the egg for fertilization. Flagellum acts as a motile whip.

Membrane Transport

• Solution is a homogenous mixture of two or more components
• Solvent is the dissolving medium present in a larger quantity; the body's main solvent is water
• Solutes are components in smaller quantities within a solution

Intracellular Fluid

• Nucleoplasm and cytosol: Solution containing gases, nutrients, and salts dissolved in water

Extracellular Fluid

• Fluid on the exterior of the cell
• Contains nutrients, hormones, neurotransmitters, salts, and waste products

Plasma Membrane

• A selectively permeable barrier: Some materials can pass through, while others are excluded
• Nutrients can enter the cell, while undesirable substances are kept out

Methods for Membrane Transport

• Passive processes- Substances are transported across the membrane without any input from the cell

Active processes

• The cell provides the metabolic energy (ATP) to drive the transport process
• The majority of ATP synthesis occurs in cellular respiration within the mitochondrial matrix

Diffusion

• Molecule movement is from high concentration to low concentration, down a concentration gradient
• Particles tend to distribute themselves evenly within a solution
• Kinetic energy (energy of motion) causes the molecules to move about randomly
• Size of the molecule and temperature affect the speed of diffusion
• Molecules will move by diffusion if any of the following applies

Simple Diffusion

• An unassisted process: Solutes are lipid-soluble or small enough to pass through membrane pores
• Small amounts of vitamins are required in the diet to promote growth, reproduction, and health
• Vitamins A, D, E, and K are called the fat-soluble vitamins, because they are soluble in organic solvents and are absorbed and transported in a manner similar to that of fats (ADEK - Lipid Soluble vitamins)

Osmosis

• Simple diffusion of water across a selectively permeable membrane
• Highly polar water molecules easily cross the plasma membrane through aquaporins
• Water moves down its concentration gradient

Isotonic Solutions

• Solutions have the same solute and water concentrations as cells and cause no visible changes in the cell (nothing will happen)

Hypertonic Solutions

• Solutions contain more solutes than the cells do; the cells will begin to shrink

Hypotonic Solutions

• Solutions contain fewer solutes (more water) than the cells do; cells will plump

Facilitated Diffusion

• Transports lipid-insoluble and large substances
• Protein membrane channels or protein molecules that act as carriers are used
• The membrane may lack special protein carriers for the transport of certain substances
• Substances may not be lipid-soluble
• Substances may have to move against a concentration gradient
• Through cellular respiration

Active Transport

• Amino acids, some sugars, and ions are transported by protein carriers known as solute pumps ATP energizes solute pumps; in most cases, substances are moved against concentration (or electrical) gradients
• Necessary for nerve impulses
• Sodium is transported out of the cell; potassium is transported into the cell

Filtration

• Water and solutes are forced through a membrane by fluid, or hydrostatic, pressure
• A pressure gradient must exist that pushes solute-containing fluid (filtrate) from a high-pressure area to a lower-pressure area
• It is critical for the kidneys to work properly

Vesicular Transport

• Substances are moved across the membrane “in bulk” without actually crossing the plasma membrane

Types of Vesicular Transport

-Exocytosis (Release), Endocytosis (Engulf) -Phagocytosis -Pinocytosis

Endocytosis

• The process by which substances are engulfed into the cell

Exocytosis

• The reverse; the process by which substances are released from the cell
• Mechanism cells use to actively secrete hormones, mucus, and other products
• Material is carried in a membranous sac called a vesicle that migrates to and combines with the plasma membrane Contents of the vesicle are emptied to the outside Docking proteins on the vesicles recognize plasma membrane proteins and bind with them Membranes corkscrew and fuse together Extracellular substances are enclosed (engulfed) in a membranous vesicle

Once in the cell, the vesicle typically fuses with a lysosome

Contents are digested by lysosomal enzymes In some cases, the vesicle is released by exocytosis on the opposite side of the cell

Phagocytosis

-Cell eating: Pseudopods engulf the external substance, then separates them from the external environment

• A protective mechanism, not a means of getting nutrients

Pinocytosis

• Cell drinking: Cell "gulps” droplets of extracellular fluid containing dissolved proteins or fats A routine activity for most cells, involved in absorption

Cell Division

• Cell life cycle is a series of changes the cell experiences from the time it is formed until it divides.
• Cell life cycle has two major periods

Interphase

• Cell grows and carries on metabolic processes and longer phase of the cell cycle

Cell Division

Cell reproduces itself

Preparations

• Genetic material is duplicated and readies a cell for division into two cells
• Occurs toward the end of interphase

Process of DNA Replication

• DNA uncoils into two nucleotide chains, and each side serves as a template
• Nucleotides always bond with each other

Mitosis

• Division of the nucleus; results in the formation of two daughter nuclei

Cytokinesis

• Division of the cytoplasm; begins when mitosis is near completion and results in the formation of two daughter cells

Prophase

• Chromatin coils into chromosomes (identical strands called chromatids) held together by a centromere
• Centrioles direct the assembly of a mitotic spindle
• Nuclear envelope and nucleoli have broken down
• Nuclear membrane breakdown results to the creation of a mitotic spindle

Metaphase

• Chromosomes are aligned in the center of the cell on the metaphase plate
• Alignment of chromosomes

Anaphase

• Centromere splits
• Chromatids move slowly apart and towards the opposite send of the cell
• Anaphase is over when the chromosomes stop moving

#####Telophase

• Reverse of prophase
• Chromosomes uncoil to become chromatin
• Spindles break down and disappear
• Nuclear envelope re-forms around chromatin
• Nucleoli appear in each of the daughter nuclei

Cytokinesis

• Division of the cytoplasm
• Begins during late anaphase and completes during telophase
• A cleavage furrow (contractile ring of microfilaments) forms to pinch the cells into two parts

Protein Syntheses

• DNA serves as a blueprint for making proteins
• GENE
  • DNA segment that carries a blueprint for building one polypeptide chain
• Proteins have many functions
  • Fibrous structural proteins
  • Globular functional proteins
• DNA information is coded into a sequence of bases.
• A sequence of three bases (triplet) codes for an amino acid.
• For example, a DNA sequence of AAA specifies the amino acid phenylalanine.
• Most ribosomes, the manufacturing sites of proteins, are located in the cytoplasm.
• DNA never leaves the nucleus in interphase cells.
• DNA requires a decoder and a messenger to carry instructions to build proteins to ribosomes.
• Both the decoder and messenger functions are carried out by RNA (ribonucleic acid).

Transcription

• Transfer of information from DNA's base sequence to the complementary base sequence of mRNA
• DNA is the template for transcription; mRNA is the product
• Each DNA triplet corresponds to an mRNA codon If DNA sequence is AAT-CGT-TCG, then the mRNA corresponding codons are UUA-GCA-AGC

Translation

• Base sequence of nucleic acid is translated to an amino acid sequence; amino acids are the building blocks of proteins.
• Occurs in the cytoplasm and involves three major varieties of RNA Steps correspond to Figure 3.16 (step 1 covers transcription)

Three Varieties of RNA

• Transfers appropriate amino acids to the ribosome for building the protein
• Helps form the ribosomes where proteins are built
• Carries the instructions for building a protein from the nucleus to the ribosome

Chapter III Body Tissues Characteristics

• Groups of cells with similar structure and function
• Four Primary Types
  • Epithelial tissue (epithelium)
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
• Epithelial Tissue/Epithelium

Locations

• Body coverings
• Body linings
• Glandular tissue

Functions

• Protection
• Absorption
• Filtration
• Secretion

Hallmarks

• Cover and line body surfaces
• Often form sheets with one free surface, the apical surface, and an anchored surface, the basement membrane
• Avascular (no blood supply)
• Regenerate easily if well nourished
• Epitheilia
• Number of Cell Layers
• Simple: One layer
• Stratified: More than one layer

Simple Epithelia

• Function in absorption, secretion, and filtration The main function is to filter

Simple Squamous

• Single layer of flat cells
• Functions*
  • Diffusion and filtration
  • Provide secretion in serous membranes

Simple Cuboidal

• Single Layer of cubelike cells
• Functions*
  • Secrection and aborption
  • Also, the propulsion of mucus or reproductive cells

Simple Columnar

  One layer of tall cells

Transitions

• no single transition between the types of cells
• has a Function in stretching to accommodate distortion to urinary structures

Stratified Epithelia

• Consist of two or more cell layers
• The main function is to provide protection

Stratified Squamous

• Named for the presence of the surface

Stratified Cuboidal

• Contains two layers of cuboidal cells functioning to provide protection

Connective Tissues

• Tissues are found throughout the body to connect the body parts

Functions

• Protection
• Provides Support
• Supplies Binding

Characteristic Of Connective Tissue

• Supplies Variations in blood
• Also supplies the Extracellular Matrix
  • Provides a Non living material that surrounds living cells

Two Main Elements of the Extracellular Matrix

    - Provides a water based ground substance along with adhesion proteins and polysaccharide molecules

Three Fiber Types

• Collagen: white
• Elastic: yellow
• Reticular: collagen

Types of tissue

Muscle Tissue

• A function that is found in both skeletal and cardiac muscles
• The function of muscles is to both contract or Shorten muscle

3 Types

• The basic structure of Skeletal muscle: Packaging muscle fibers into connective sheets that, in turn, attach to different skeletons
• The basic function to cardiac muscles is to provide muscle to what is the heart Smooth- Found in the walls of hollow organs such as stomach, uterus, and blood vessels

Explore cell structures and processes like membrane transport, fluid types, and cell specialization. Learn about white blood cells, fat cells, and nerve cells. Understand apoptosis, necrosis, and the role of the nucleolus.