A&P Slideshow Chapter 3

_____ are the structural units of all living things.

• cells

The human body has __ to __ cells.

• 50 to 100 trillion

What is cell theory?

• the cell is the smallest unit of life

• all organisms are made of one or more cells

• cells arise only from other cells

What is cell diversity?

• thousands of different types of human cells

• types differ in size, shape, and sub cellular components; these differences lead to differences in functions

What 3 basic parts do all human cells have?

1. plasma membrane

2. cytoplasm

3. nucleus

What is the plasma membrane?

• flexible outer boundary acts as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF)

• plays dynamic role in cellular activity by controlling what enters and what leaves cell

• also known as the “cell membrane”

What is cytoplasm?

• intracellular fluid containing organelles

What is the nucleus?

• DNA containing control center

What are extracellular materials?

• substances found outside cells

• classes of extracellular materials include:

  • extracellular fluids (ECFs)

  • cellular secretions (e.g., saliva, mucus, gastric fluids)

  • extracellular matrix

What are extracellular fluids (ECFs)?

• body fluids including:

  • interstitial fluid: cells are submersed (bathed) in this fluid

  • blood plasma: fluid of the blood

  • cerebrospinal fluid: fluid surrounding nervous system organs

What are some examples of cellular secretions?

• e.g., saliva, mucus, gastric fluids

What is extracellular matrix?

• substance that acts as glue to hold cells together

What plays a dynamic role in cellular activity by controlling what enters and what leaves the cell?

• plasma membrane

What is the fluid mosaic model of the plasma membrane?

• depicts a moving membrane made of many pieces:

  • bilayer of phospholipids with smaller amounts of cholesterol

  • embedded membrane proteins

Membrane structures help to hold cells together through _____.

• cell junctions

What is the lipid bilayer made up of?

• mostly phospholipids, which consist of 2 parts:

  • phosphate heads

  • fatty acid tails

• 20% cholesterol

  • located between the phospholipid tails

  • increases stiffness of the membranes

What are phosphate heads?

• are polar (charged), so are hydrophilic (water-loving)

What are fatty acid tails?

• are non polar (no charge), so are hydrophobic (water-hating)

Where is the cholesterol located in a lipid bilayer and what does it do?

• located between the phospholipid tails

• increases stiffness of the membrane

What are membrane proteins?

• allow cell communication with environment

• make up about half the mass of plasma membrane

• most have specialized membrane functions

• some float freely, and some are tethered to intracellular structures

What makes up about half the mass of the plasma membrane?

• membrane proteins

What are the 2 types of membrane proteins?

• integral proteins

• peripheral proteins

What are integral proteins?

• inserted into membrane; most are transmembrane proteins (span membrane)

• have both hydrophobic region that interact with lipid tails and hydrophilic regions that interact with water inside and outside the cells

• function as:

  • transport proteins (channels and carriers)

  • enzymes

  • receptors

What do integral proteins function as?

• transport proteins (channels and carriers)

• enzymes

• receptors

What are peripheral proteins?

• loosely attached to integral proteins or anchored to the membrane

• function as:

  • enzymes

  • motor proteins for shape change during cell division and muscle contractions

  • cell-to-cell connections

What do peripheral proteins function as?

• enzymes

• motor proteins for shape change during cell division and muscle contractions

• cell-to-cell connections

What tasks do membrane proteins perform?

a) transport

b) receptors for signal transduction

c) enzymatic activity enzymes

d) cell-cell recognition

e) cell-to-cell joining

f) attachment to the cytoskeleton and extracellular matrix (ECM)

Explain how a membrane protein performs the transport task.

• transport proteins allow cells to control which substances enter or exit the cell

• a protein (left) that spans the membrane may provide a hydrophilic channel across the membrane that is selective for a particular solute

• other transport proteins move a substance from one side to the other by changing shape

  • pumps use the power of ATP to drive the shape change; carriers do not require ATP

Do pumps or carriers use ATP?

• pumps use the power of ATP to drive the shape change

• carriers do not require ATP

Explain how membrane proteins perform the receptors for signal transduction” task.

• receptors allow a cell to receive information from other cells

• a receptor’s extracellular binding site fits the shape of a specific chemical messenger, such as a hormone

• binding the chemical messenger causes the protein to change shape, which initiates a chain of chemical reactions in the cell

  • this is called signal transduction and effectively moves the message from outside of the cell to inside it

What is signal transduction?

• binding the chemical messenger causes the protein to change shape, which initiates a chain of chemical reactions in the cell called signal transduction

• effectively moves the message from outside of the cell to inside it

Explain how membrane proteins perform enzymatic activity.

• enzymes in the membrane allow cells to transform one substance into another

• the active site of the enzyme may face the solution on either side of the membrane

• a team of several enzymes in a membrane may catalyze sequential steps of a metabolic pathway

Explain how membrane proteins perform cell-cell recognition.

• some proteins in the membranes of adjacent cells allow them to recognize each other through direct physical contact

• some glycoproteins (proteins bonded to short chains of sugars which help to make up the hlycocalyx) serve as identification tags that are specifically recognized by other cells

• this type of cell-cell binding is usually short-lived compared with cell-to-cell joining

Explain how membrane proteins perform cell-to-cell joining.

• membrane proteins of adjacent cells may be hooked together in various kinds of long-lasting intercellular junctions (e.g., tight junctions and gap junctions)

• some membrane proteins (cell adhesion molecules, or CAMs) of this group provide more short-lived binding sites that guide cell migration and other cell-to-cell interactions

Explain how membrane proteins perform the attachment to the cytoskeleton and extracellular matrix (ECM).

• some membrane proteins anchor elements of the cytoskeleton (cell’s internal framework) and the extracellular matrix (fibers and other substances outside the cell)

• helps maintain cell shape, fixes the location of certain membrane proteins, and plays a role in cell movement

What is glycocalyx?

• consists of sugars (carbohydrates) sticking out of cell surface

  • some sugars are attached to lipids (glycolipids) and some to proteins (glycoproteins)

• every cell type has different patterns of this “sugar coating”

  • functions as specific biological markers for cell-to-cell recognition

  • allows immune system to recognize “self” vs “non self”

_____ junctions allow adjacent cells to adhere or communicate.

• intercellular

What are the 3 types of cell junctions.

• tight junctions

• desmosomes

• gap junctions

What are tight junctions?

• integral proteins on adjacent cells fuse to form an impermeable junction that encircles whole cell

• prevents fluids and most molecules from moving in between cells

• create 2 compartments, one on each side of the layer of cells

What are desmosomes?

• anchoring junctions

• rivet-like cell junction formed when linker proteins (cadherins) of neighboring cells interlock like teeth of a zipper

• linker protein is anchored to its cell through thickened “button-like” areas on inside of plasma membrane called plaques

• keratin filaments connect plaques inter cellularly for added anchoring strength

• help keep cells from leaving apart

What are gap junctions?

• transmembrane proteins (connexions) form tunnels that allow small molecules to pass from cell to cell

• used to spread ions, simple sugars, or other small molecules between cells

• allows electrical signals to be passed quickly from one cell to next cell

  • used in cardiac and smooth muscle cells

What are 2 essential ways substances cross the plasma membrane?

• passive transport: no energy is needed

• active transport: energy (ATP) is required

What is passive transport?

• requires no energy input

• all molecules have random, high-speed movement due to their intrinsic kinetic energy that result in collisions between molecules

• molecules in higher concentration areas collide more, resulting in molecules being scattered to lower concentration areas

What are the 3 types of passive transport?

• simple diffusion

• facilitated diffusion

• osmosis

All types of passive transport involve _____.

• diffusion

What is diffusion?

• natural movement of molecules from areas of high concentration to areas of low concentration

  • also referred to as moving down a concentration gradient

_____ is also referred to as moving down a concentration gradient.

• diffusion

What 3 factors is the speed of diffusion influenced by?

• concentration— the greater the difference of concentration between 2 areas, the faster diffusion occurs

• molecular size— smaller molecules diffuse faster

• temperature— higher temperature increase kinetic energy which results in faster diffusion

The system reaches equilibrium when there is _____ of molecules in one direction.

• no net movement

The plasma membrane is _____ permeable.

• selectively, or differentially

What does the plasma membrane being selectively permeable mean?

• allows nutrients to enter the cell, but prevents many undesirable substances from entering

• keep valuable cell proteins and other necessary substances in the cell, but allows wastes to exit

_____ core of plasma membranes stops diffusion and creates concentration gradients by acting as selectively permeable barriers. (hydrophobic/hydrophilic)

• hydrophobic

What is simple diffusion?

• lips-soluble molecules and small molecules can cross plasma membrane

• substance diffuse directly through the lipid bilayer

• nonpolar lipid-soluble (hydrophobic) substances diffuse directly through phospholipid bilayer

• Ex: oxygen, carbon dioxide, steroid hormones, fatty acids

• small amounts of very small polar substances such as water, can even pass

What are examples of substances that go through simple diffusion?

• oxygen, carbon dioxide, steroid hormones, fatty acids

• small amounts of very small polar substances, such as water, can even pass

What is facilitated diffusion?

• transport across the plasma membrane with assistance of carrier or channel protein

  • certain hydrophobic molecules (e.g., glucose, amino acids, and ions) are transported passively with assistance down their concentration gradient

• carrier-mediated facilitated diffusion

• channel mediated facilitated diffusion

• water-soluble molecules and large molecules require assistance crossing plasma membrane

What are 2 types of facilitated diffusion?

• carrier-mediated facilitated diffusion

  • substances bind to protein carriers

• channel-mediated facilitated diffusion

  • substances move through water-filled channels

What is carrier-mediated facilitated diffusion?

• carriers and transmembrane integral proteins that transport specific polar molecules, such as sugars and amino acids, that are too large for membrane channels

• binding of molecule causes carrier to envelope it and change shape that results in molecule being moved across membrane

• carriers are saturated when all are bound to molecules and are busy transporting

Carriers are _____ when all are bound to molecules and are busy transporting.

• saturated

What is channel-mediated facilitated diffusion?

• channels are transmembrane proteins with aqueous-filled cores that transport molecules, such as ions, down their concentration gradient

  • specificity based on pore size and/or large

• 2 types:

  • leakage channels which are always on

  • gated channels which are controlled by chemical or electrical signals

What are leakage channels?

• a type of channel-mediated facilitated diffusion channels

• always on

What are gated channels?

• a type of channel-mediated facilitated diffusion channels

• are controlled by chemical or electrical signals

What is osmosis?

• the movement of water through a selectively permeable membrane

• extremely important in determining the distribution of water in the various fluid containing compartments of the body

• water diffuses across plasma membranes

  • through lipid bilayer (even though water is polar, it is so small that some molecules can sneak past non polar phospholipid tails)

  • through specific water channels called aquaporins (AQPs)

• osmosis occurs whenever the solute concentration differs on the 2 sides of a membrane

What is osmolarity?

• total concentration of all solute particles in a solution

When solute concentration goes up —> _____.

• water concentration goes down

Water moves by osmosis from areas of _____ solute concentration to areas of _____ solute concentration.

• low solute concentration to high solute concentration

How is osmolarity expressed?

• osmoles/liter (osmol/L)

What is equilibrium?

• same concentration of solutes and water molecules on both sides, with equal volume on both sides

When solutions of different osmolarities are separated by a membrane that is permeable only to water, only _____ will occur until equilibrium is reached.

• only osmosis (not diffusion)

What 2 pressures does the movement of water involve?

• hydrostatic pressure

• osmotic pressure

What is hydrostatic pressure?

• the back pressure exerted by water against the cell wall

What is osmotic pressure?

• the tendency of water to move into the cell by osmosis

When hydrostatic pressure _____ osmotic pressure, no further net movement of water occurs.

• equals (water trying to exit equals water trying to enter)

Why can animal cells not limit hydrostatic and osmotic pressures like plant cells?

• plant cells are surrounded by strong cell walls that limit hydrostatic pressure levels, which limits osmotic pressure

• animal cells do not have cell walls, and therefore cannot limit hydrostatic and osmotic pressures

Osmotic imbalances cause animal cells to _____ or _____.

• swell or shrink

Why do osmotic imbalances cause animal cells to swell or shrink?

• due to net water gain or loss

What is tonicity?

• ability of a solution to change the shape ,or plasma membrane tension, of cells by altering the cells’ internal water volume

What is an isotonic solution?

• has same osmolarity as inside the cell, so volume remains unchanged

What is a hypertonic solution?

• has higher osmolarity than inside cell, so water flows out of cell, resulting in cell shrinking

  • shrinking is referred to as crenation

What is cell shrinking referred to as?

• crenation

What is crenation?

• cell shrinking

What is hypotonic solution?

• has lower osmolarity than inside cell, so water flows into cell, resulting in cell swelling

  • can lead to cell bursting, referred to as lysing

What is cell bursting referred to as?

• lysing

What is lysing?

• cell bursting

An _____ process occurs whenever cell uses energy directly or indirectly to move solutes across the membrane against their concentration gradient (from low to high).

• active (requires energy (ATP))

What are 2 major active membrane transport processes?

• active transport

• vesticular transport

Why might active or vesticular transport reuiqre ATP to move solutes across a plasma membrane?

• solute is too large for channels

• solute is not lipid soluble

• solute is not able to move down concentration gradient

What is primary active transport?

• energy to do work ones directly from hydrolysis of ATP by transport proteins called pumps

• energy from hydrolysis of ATP causes change in shape of transport protein, which causes solutes (ions) bound to protein to be pumped across membrane

• examples of pumps: calcium, hydrogen (proton), Na+ -K+ pumps

What is secondary active transport?

• energy stored in concentration gradients of ions created by primary active transport pumps

• always move more than one substance at a time using a con transport protein

What is a sodium-potassium pump?

• most studied pump

• the pump protein is a enzyme Na^+ -K^+ ATPase, that pumps 3Na^+ out of cell and 2K^+ into cell for each ATP molecules used

• located in all plasma membranes, but especially active in excitable cells (nerves and muscles)

What is secondary active transport?

• also called cotransport

• depends on ion gradient that was created by primary native transport systems,

• energy stored in gradients is used indirectly to drive transport of other solutes

  • Low Na concentration that is maintained inside cell by Na -K pump strengthens sodium’s drive to want to enter cell

  • Na can drag other molecules with it as it flows into cell through carrier proteins (usually supporters) in membrane

What are supporters?

• transport 2 different substances in the same direction

What are antiporters?

• transport 1 substance into cell while transporting it

What is vesticular transport?

• moves large substances, or large amounts of a substance, across cellular membranes inside bubble-like, membranous sas called vesicles

  • requires cellular energy (usually ATP)

What are the 4 types of vesticular transport?

• transcytoosis

• vesicular trafficking

• endocystosis

• exocytosis

What is transcytosis?

• moves substances into, across, and then out of the cell

What is vesicular trafficking?

• moves substances from one area (or membranous organelle) in the cell to another

What is endocytosis?

• transport into cell

• involves formation of protein-coated vesicles

• usually involve receptors, and therefore, can be a very selective process

  • substance being pulled in must be able to bind to its unique receptor

• some pathogens are capable of hijacking receptor for transport into cell

• once veislce isp pulled inside cell, it may:

  • fuse with lysosome or

  • undergo transcytosis

• phagocytosis, pinocytosis, receptor-mediated endocytosis

What is exocytosis?

• transport out of cell

What is phagocytosis?

• type of endocytosis that is referred to as “cell eating”

  • membrane projections called pseudopods form and flow around solid particles that are being engulfed, forming a vesicle which is pulled into the cell

  • is sued by macrophages and certain other white blood cells

What is the formed vesicle in phagocytosis called?

• phagosome