A&P Chapter 3

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Which of the following statements correctly describes the plasma membrane?

It is a dynamic fuid structure that is in constant flux.

Which of the following factors act to bind cells together?

Specialized junctions, wavy membrane contours, and glycoproteins.

Why is the selective permeability of the plasma membrane essential for normal cell function?

Selective permeability allows cells to exclude some substances and allow others to pass into or out of the cell.

What is the difference between active and passive transport across the plasma membrane?

Active transport is ATP dependent, whereas passive transport uses only the kinetic energy of the particles for movement across the plasma membrane

What is a membrane potential?

A voltage or electric charge across the plasma membrane.

Which cell organelle provides the majority of the ATP needed by the cell to carry out its metabolic reactions?


Which of the following is a function of the rough endoplasmic reticulum?

Synthesis of the cell’s membranes.

Which cell component helps to maintain the structural integrity of the cell?


What must happen before a body cell can begin mitotic cell division?

It’s DNA must be replicated exactly so that identical copies of the cell’s genes can be passed on to each of its offspring.

What are the two basic steps of polypeptide synthesis?

Transcription and translation.


Depending where the cell is located, the function can be very different.

Generalized cell

All cells have some common functions. Human cells have three basic parts: plasma membrane- flexible outer boundary. Cytoplasm- intracellular fluid containing organelles. Nucleus- control center.

Plasma membrane

Lipid bilayer and proteins in constantly changing fluid mosaic. Plays dynamic role in cellular activity. Separates intracellular fluid form extracellular fluid. Intersitial fluid = extracellular fluid that surrounds the cells.

Membrane lipids

75% phospholipids (lipid bilayer) -phosphate heads: polar and hydrophilic. -Fatty acid tails: non-polar and hydrophobic. 5% gylcolipids -Lipids with polar sugars on outer membrane surface. 20% cholesterol -Increases membrane stability.

membrane proteins

Allow communication with environment. 1/2 mass of plasma membrane. Most specialized membrane functions. Some float freely. Some tethered to intracellular structures. Two types: -integral proteins, peripheral proteins.

Integral proteins

Firmly inserted into membrane (most are transmembrane ). Have hydrophobic and hydrophilic regions. – Can interact with lipid tails and water. Functions as transport proteins (channels and carrier, enzymes, or receptors.

Peripheral proteins

Loosely attached to integral proteins. Include filaments on intracellular surface for membrane support. Function as enzymes; motor proteins for shape change during cell division and muslce contraction; cell-to-cell connections.

Six functions of membrane proteins

1. Transport 2. Receptors for signal transduction 3. Attachment to cytoskeleton and extracellular matrix 4. Enzymatic activity 5. Intracellular joining 6. Cell-cell recognition

The gylcocalyx

"Sugar covering" at cell surface -lipids and proteins with attached carbohydrates (sugar groups). Every cell type has different patterns of sugars. -Specific biological markers for cell to cell recognition. -Allows immune system to recognize "self" and "non-self." -Cancerous cells change it continuously.

Cell junctions

Some cells "free" -e.g., blood cells, sperm cells. Some bound into communities. Three ways cells are bound: -Tight junctions: prevents fluids leaking. -Desmosomes: Velero -Gap junctions: Communicating.

Plasma membrane cont..

Cells surrounded by interstitial fluid -contains thousands of substances, e.g, amino acids, sugars, fatty acids, vitamins, hormones, salts, waste products. Plasma membrane allows cells to -obtain from interstitial fluid exactly what it needs, exactly when it is needed. -Keep out what it does not need. Plasma membrane is selectively permeable.

Types of membrane transport

Passive processes (high to low concentration) -no cellular energy (ATP) required. -substance moves down its concentration gradient. Active processes (low to high concentration) -energy (ATP) required -occurs only in living cell membranes

Passive Processes: Osmosis

Movement of solvent (e.g., water0 across selectively permeable membrane. Water diffuses through plasma membranes. -Through lipid bilayer -Through specific water channels called aquaporins. Occurs when water concentration different on the two sides of a membrane. * Water moves until equilibrium is reached

Importance of osmosis

Osmosis causes cells to swell and shrink Change in cell volume disrupts cell function, especially in neurons. *red blood cell has to be healthy


Ability of solution to alter cell’s water volume. -isotonic: solution with same no-penetrating solute concentration as cytosol. Ex: 0.9% NaCl, 99.1% H2O. Equal. -hypertonic: solution with higher non-penetrating solute concentration than cytosol. Ex: 2% NaCl, 98% H2O. Shrink. -hypotonic: solution with lower non-penetrating solute concentration than cytosol. Ex: 100% H2O. Burst.

Active Processes

There are two types: -Active transport -Vesicular transport Both require ATP to move solutes across a living plasma membrane because -solutes too large for channels -solute not lipid soluble -solute not able to move down concentration gradient

Active transport

Requires carrier proteins (solutes pumps) -binds specifically and reversibly with substance. Moves solutes against concentration -requires energy.

Two types of active transport

Primary active transport -requires energy directly from ATP hydrolysis Secondary active transport -requires energy indirectly from ionic gradients created y primary active transport (kinetic)

Secondary active transport

Cotransport- always transports more than one substance at a time. -symport system: substances transported in same direction -antiport system: subatances transported in opposite directions.


Drinking liquids

Receptor mediated endocytosis

hormone binding to receptor


Located in plasma membrane -cytosol -organelles -inclusions


-mitochondria -peroxisomes -lysosomes -endoplamic reticulum -golgi apparatus


-cytoskeleton -centriole -ribosomes


site of protein synthesis contain protein and rRNA

Endoplasmic Reticulum

two types: rough endoplasmic reticulum smooth endoplasmic reticulum

Rough endoplasmic reticulum

Synthesis of cell’s membranes

Smooth endoplasmic reticulum

absorption, synths, and transport of fats

Golgi apparatus

modifies, concentrated, and packages proteins and lipids from rough ER


Catalysis and synthesis of fatty acids


Digest ingested bacteria, viruses, and toxins.


proteins link rods to to other cells structures. -microfilaments -intermediate filaments -microtubles


Thinnest, involved in cell motility, change in shape, and endocytosis and exocytosis.

Intermediate filaments

Ropelike fibers, attach to desmosomes.


Largest, controsomes, determine overall shape of cell and distributing of organelles.

Centrosome and centriole

"cell center" near nucleus. contains paired centrioles,

Cilia and flagella

Cilia move substances across cell surfaces. Longer flagella propel whole cells.


Larest organelles. Three regions/structures. Uninucleate, multinucleate, and a nucleate.

Cell division

Meiosis- cell division producing gametes mitotic cell division- produces clones -essential for body growth and tissue repair


Division of nucleus. 4 stages: prophase, metaphase, anaphase, and telophase.


Division of cytoplasm.


DNA info coded into mRNA. Transfers DNA gene base sequence to complementary base sequence of mRNA.


mRNA decoded to assemble polypeptide. Converts base sequence of nucleus acids into amino acid sequence of proteins. Involves mRNA, tRNA, and rRNA.

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