BIOL 2111-02 Chapter 3 (Organs of a Cell, Histology)

(Organs of a Cell, Organelle Functions, Membrane Permeability, Passive Transport, Active Transport (ATP))

“The cell is…

… The structural/functional unit of life.”

Cell Diversity

Over 200 different types of human cells

Cell Life Cycle

Series of changes a cell undergoes from the time it is formed until it reproduces (Interphase and Mitotic Phase)

Interphase

The cell grows and carries out its usual activities

Mitotic Phase

Phase where cell divides

Mitosis

Cell replacement and growth

Diploid (2n)

two sets of chromosomes (one from each parent)

Haploid (n)

Contain one set of chromosomes (half the number of diploid cells)

Meiosis

Form gametes (eggs/sperm) for reproduction

Information Pathway

1. DNA

2. Trasncription

3. RNA

4. Translation

5. Protein

Function of a Protein…

Determines the cells functions

Plasma Membrane

Acts as a barrier, separating intra cellular fluid from extracellular fluid.

Plasma Membrane Structure

Fluid mosaic pattern (composed of a double layer of phospholipids embedded with cholesterol and proteins)

Membrane Functions

1. Phospholipids

2. Cholesterol

3. Glycocalyx

4. Proteins

Phospholipids

Provide a fluid, flexible area or barrier

Cholesterol

Stabilize the membrane and reduce membrane fluidity

Glycocalyx

Surface sugars, either glycolipids or glycoproteins, play a role in cell recognition

Proteins in Membrane Functions

Act as transporters, receptors in signal transduction, attachment to cytoskeleton, enzymes, intracellular joining, and cell-cell identifiers.

Integral Proteins

Firmly inserted into the membrane, most completely span membrane, so also called transmembrane proteins.

Peripheral Proteins

Loosely attached edge membrane.

Membrane Receptor Proteins

Serve as binding sites for chemical ligands to indirectly initiate activity change inside the cell. When chemical ligand binds, receptor protein changes shape and thereby becomes activated.

G Protein-Couple Receptors (GPCR)

Receptor binds largest and most diverse group of membrane receptors in eukaryotes.

Cytoplasm

All cellular material that is located between the plasma membrane and the nucleus.

Nucleus

Largest organelle and houses most of the cell’s DNA

Uninucleate

One nucleus, found in majority of cells

Multunucleate

Many nuclei per cell, found in skeletal muscle

Anucleate

No nucleus, found in red blood cells

Mitochondria

Produces most of the cell’s energy molecules (ATP), which is produced via aerobic cellular respiration, and contains its own DNA

Ribosomes

Is the site of protein synthesis

Free floating ribosomes

produces soluble proteins.

Ribosomes bound to the RER

Produces proteins for the membrane or out of the cell

Rough Endoplasmic Reticulum

Series of parallel, interconnected flattened membranous tubes that are studded with ribosomes. Ribosomes synthesis into proteins and are modified and then sent to the golgi apparatus.

Smooth Endoplasmic Reticulum

Network of looped tubules and site of lipid synthesis.

Function of SER

Detox chemicals, stores calcium, converts glycogen into free glucose and ATP.

Golgi Apparatus

Stacked and flatted membrane sacs which receives vesicles from the RER and modifies/packages proteins.

Three pathways after the Golgi Apparatus

Secretory Vesicle, Plasma Membrane, Lysosome

Lysosome

Membrane bound sac that contains digestive enzymes.

Lysosome Functions

Digest ingested bacteria (virus/toxins), degrade old organelles

Peroxisomes

Membrane bound sac that contains powerful detoxifying substances that neutralize free radial toxins and break down fatty acids.

Cytoskeleton

Elaborate network of rods that run throughout the cytoplasm.

Microfilaments

Shape microvile

Intermediate Filaments

Resist pulling forces and acts as an ancor

Microtubules

Large tubes which determines a cell’s shape and movement

Cellular Extensions

Certain cells have structures extending from the cells surface.

Cilia Hair

Extensions with whip-like action, used to move things along the surface

Flagella

Long extensions which are used to propel the whole cell

Microvilla

Small fingerlike extensions of the plasma used to INCREASE SURFACE AREA and for absorption.

Membrane Junctions

Tight junctions, desmosomes, gap junctions

Tight Junctions

proteins on adjacent cells fuse to form tissues and organs

Desmosomes

Rivet-like junction, similar to a zipper which opens between cells.

Gap Junctions

Proteins form tunnels to allow small molecules to pass between cells.

Membrane Permeability

Plasma membrane is selectively permeable, which means, it allows some materials to move freely and restrict others.

Permable

small molecules, non-polar, non-charged, liquid soluble, and hydrophobic

Impermable

large molecules, polar, charged, and hydrophilic.

Examples of what CAN PASS through the membrane

oxygen, small gases and lipids, ethanol, and some vitamins

Examples of what CANNOT PASS through the membrane

Amino Acids, Glucose, Nucleotides, Water, and Ions

The plasma membrane is a…

Semipermeable Membrane

Membrane transport is determined by…

THE CONCENTRATION GRADIENT

The two types of transport in the membrane

Passive and Active Transport

Passive Transport

going ACROSS the gradient from HIGH TO LOW, going DOWN the gradient

Active Transport

Going AGAINST the gradient from LOW TO HIGH, going UP the gradient

Transport requires ATP

Active Transport

Types of Passive Transport

Simple diffusion, facilitated diffusion, and osmosis.

Type of passive membrane is determined by

Determined by the membrane permability

Diffusion

Random mixing of particles, where movement occurs until equilibrium.

Simple Diffusion

Movement of molecules DIRECTLY through a PERMABLE MEMBRANE, does not require transport proteins, and no ATP.

Facilitated Diffusion

Utilizes an TRANSPORT PROTEIN to allow IMPERMABLE MOLECULES to be transported across the plasma membrane.

Types of Transport Proteins

Carriers and Channels

Carrier Proteins

Changes shape to SHUTTLE SOLUTES across the outer membrane

Channel Proteins

Tunnel and corridor inside the outer membrane

Characteristics of Transport Proteins

Specific to each molecule with competition, molecules move DOWN the concentration gradient, and NO ATP is required.

Osmosis

diffusion of WATER across a selectively permeable membrane,

Characteristics of Osmosis

AQUAPORIN CHANNEL, special kind of FACILITATED DIFFUSION, WATER FOLLOWS SOLUTES

Osmotic Pressure

Water Movement

Tonicity

The ability of a solution to change the shape/tone of a cell by ALTERING internal WATER VOLUME due to IMPERMABLE SOLUTES.

Three types of solutions

Isotonic, Hypertonic, Hypotonic

Iso

The same

Isotonic

SOLUTION CONCENTRATION is EQUAL to the concentration INSIDE THE CELL.

Hypertonic

SOLUTION CONCENTRATION is GREATER than the concentration INSIDE THE CELL.

Hypotonic

SOLUTION CONCENTRATION is LESS than the concentration INSIDE THE CELL.

Cell shape in a Hypertonic solution

Cell’s shape will shrink

Example of a hypertonic solution

The solution’s concentration is greater than the cell, so the cell must donate water to the solution, causing the cell to become small.

Cell shape in a Hypotonic Solution

Cell’s shape is large

Example of a hypotonic solution

The solution’s concentration is less than the cell, so the solution must donate water to the cell, causing the cell to become large.

Active Transport

Moves substances from an area of low concentration to high concentration (ATP required)

Transport Proteins are needed ALL THE TIME

Active Transport always needs

Primary Active Transport

Energy derived from direct hydrolysis of ATP

Example of Primary Active Transports

Proton pumps, Ca-pump, Sodium-potassium pump

Na-K pump moves…

3 Na+ out of the cell, and 2 K+ into the cell

Functions of a Na-K Pump

Maintains ion imbalance, cell volume, membrane polarity, and is the drive for secondary active transport

Secondary Active Transport

The kinetic energy from one molecule’s concentration gradient drives the active transport of another substance.

Example of secondary active transport

While sodium moves DOWN the gradient, another molecule is able to move UP the gradient.

Co-transporter

Secondary Active Transport always uses

Function of Secondary Active Transport

bringing nutrients into the body

Three Active Transports

Primary, secondary, and bulk transport

Bulk Transport

Named by the DIRECTION moving with the cell (exocytosis and endocytosis)

Exocytosis

Materials leave the cell

Endocytosis

Materials move into the cell

Exo

Exit

Endo

Enter