OVERVIEW

1. Historical – cells from cells; use to think living from dead material

2. Cell theory – basic unit of life; continuity; cells from cells

3. Shape - dependent on function

4. Number - trillions of cells in our bodies

5. Length – from 2 micrometers to over a meter (nerve)

6. Structure – generalized, animal, composite, human; 3 basic parts

-a. Nucleus - centrally located and controls cellular activity

-b. Cytoplasm - surrounds the nucleus and contains organelles

-c. Plasma membrane - surrounds the cell and forms its boundary

PLASMA MEMBRANE: STRUCTURE

Fluid Mosaic Model

1. Fluid Mosaic Model – proteins embedded in lipid bilayer; move; change pattern

2. Phospholipid bilayer - have both a polar and nonpolar portion

-a. Hydrophobic - nonpolar tails; lie tail to tail to each other

-b. Hydrophilic - polar heads face the water both inside and outside

3. Glycolipids - lipids with attached sugars are attached to 10% of the polar heads

4. Cholesterol - substantial amounts; help stabilize the membrane

5. Proteins - 50% of the membrane by weight

6. Integral proteins - inserted into membrane; one side and transmembrane

-a. Functions - transportation, enzymes, transport, etc.

7. Peripheral proteins - not embedded in usually to exposed integral protein

-a. Cytoskeletal attachment – peripherals on cytoplasm side

-b. Glycoproteins – many on extracellular fluid side

8. Glycocalyx – sugar coating; from glycolipids and glycoproteins

-a. Function – binds cells; recognition

PLASMA MEMBRANE: FUNCTION

Membrane Transport

Passive processes vs. active processes

1. Passive processes – do not depend on ATP to ADP; (energy used)

2. Active processes – energy is going to be used; ATP to ADP

Passive processes: diffusion

1. Diffusion – down a concentration gradient; kinetic energy; from lesser to greater

2. Simple diffusion – mechanisms depend on polarity

-a. Nonpolar - lipid soluble molecules; directly through bilayer; gases; fats; alcohol

-b. Polar substances – can move through water filled protein channels; small enough

-c. Ions – also through water filled pores

-d. Selectivity – size, gated; sometimes open, sometimes not

2. Facilitated diffusion – larger polar molecules; glucose

-a. Membrane proteins – envelope; change shape; release

Passive processes: osmosis

1. Osmosis - diffusion of a solvent, water, through selectively permeable membrane

2. Concentration gradient – water moves toward higher solute concentration

-a. Higher solute concentration – water molecules less concentrated

-b. Down concentration gradient – water moves from higher to lesser concentration

3. Tonicity - ability to change the tone or shape of cells by altering water volume

-a. Isotonic – solute concentration is equal to the cell; no effect on cell

-b. Hypertonic – solute concentration greater than cell; water moves out; shrinkage

-c. Hypotonic - solutes concentration less than cell; water moves in; swell; burst

Passive Processes: filtration

1. Filtration – water, solutes forced through membrane by hydrostatic pressure

2. Pressure gradient - Solute containing fluids from greater to less pressure

3. Examples – capillaries and kidneys

Active processes: active transport

1. Active transport - solutes moved against concentration gradient

2. Solute pump – another name for this process

3. ATP - energy to do this work against the concentration gradient

-a. Carrier protein – ATP to ADP, change in protein so it can move solute

4. Symport system - two substances in the same direction

5. Antiport system - substances in different moved in different directions

6. Primary active transport – carrier molecule, phosphate attached; does job

-a. Na⁺K⁺ pump – antiport; Na out K; Na⁺K⁺ATPase

7. Secondary active transport - passive ion gradient from primary active transport

-b. Glucose – other solutes; transported with Na; symport

Active processes: vesicular transport

1. Bulk transport – also called; moves large macromolecules

2. Exocytosis - from the cell interior into extracellular space; secretion

3. Endocytosis - fluid, particles enter the cell

-a. Phagocytosis - (cell eating) large external particles white blood cells

-b. Pinocytosis - (cell drinking) membrane sinks beneath an external fluid droplet

Other Membrane Functions

Resting Membrane Potential

1. Potential – voltage; separation of oppositely charged particles

2. Membrane potential – membrane separates oppositely charged particles; ions

3. Resting membrane potential - -20 to -200 millivolts (mV); inside slightly negative

4. Generating resting membrane potential – difference in K and Na permeability

-a. Potassium ions – more inside; move out; more permeable to potassium

-b. Sodium ions – more outside; move in; less permeable to sodium

-c. Negative – inside cell due to more negative moving out

5. Maintaining resting membrane potential – continually move Na⁺ out and K⁺ in

-a. Na⁺K⁺ ATPase – pumps 3 Na⁺ out for every 2 K⁺ it pumps in

-b. Equilibrium – sodium would move in; membrane potential would be lost

Cell-Environment Interactions

1. Glycocalyx – sugary coating; interactions; CAMs or membrane receptors

2. Cell adhesion molecules – cell mobility; wound repair, immunity, development

3. Membrane receptors – integral proteins and glycoproteins; binding sites

-a. Contact signaling- used for cell recognition

-b. Electrical signaling – voltage change; open and close ion gates

-c. Chemical signaling – most; like neurotransmitters and hormones

CYTOPLASM

General

1. Cytoplasm - cellular material inside plasma membrane, outside nucleus

2. Components - of the cytoplasm

-a. Cytosol - viscous fluid, mostly water; soluble proteins, salts, other solutes

-b. Inclusions - nonfunctioning units; include: glycogen, lipid droplets, etc.

-c. Cellular organelles - the metabolic machinery of the cell

Cytoplasmic Organelles

General remarks

1. Little organs – what the word means

2. Function – each have their own function

3. Membranes - similar to plasma membrane prevents mixing of contents (enzymes)

Mitochondria

1. Shape – rod, sausage shape to thread like (but can vary)

2. Membranes -2 enclose the mitochondria

-a. Smooth - outer membrane

-b. Cristae - shelf like inner protrusions of the inner membrane

-c. Matrix - the gel like substance inside of the mitochondria

2. Power house - of the cell site of aerobic (oxygen required)

-a. Cellular respiration - where glucose is broken down to carbon dioxide and water

-b. ATP production - energy released used to attach a phosphate group to ADP

3. Number - metabolically active cells; muscle and liver, have many

4. Self replicating - DNA and RNA; undergo fission and then grow

Ribosomes

1. Ribosomes - small dark stained granules; ribosomal RNA, protein

2. Subunits - a smaller one sitting on top of a larger one (figure 3.15c p. 80)

3. Protein synthesis – where this takes place

4. Free ribosomes - which produce cytosol proteins

5. Membrane bound ribosomes – produce integral membrane and export proteins

Endoplasmic reticulum

1. Network - of interconnected tubes and parallel membranes

2. Cisternae - fluid filled cavity enclosed by the endoplasmic reticulum

3. Nuclear envelope - continuous with it

4. Rough endoplasmic reticulum

-a. Ribosomes - external surface is studded with

-b. Excretory proteins – synthesized; abundant in secretory, liver, antibody produce

-c. Membrane factories – integral proteins and phospholipids

5. Smooth endoplasmic reticulum -continuation of the rough ER

-a. Tubules - arranged in a branching network

-b. Functions - lipid synthesis and metabolism, steroid synthesis, drug detoxification

Golgi apparatus

1. Golgi apparatus - stack of flattened membranous sacks with many vesicles

2. Functions – use material delivered from vesicles from rough ER to make

-a. Secretory vesicles – for extracellular transport; exocytosis

-b. Plasma membrane - components fuse with plasma membrane

-c. Lysosomes – discussed now

Lysosomes

1. Digestive enzymes – contained in the lysosome; breakdown most molecules

2. Functions – all related to digestive enzymes

-a. Phagocytes – immunity; digestion phagocytized bacteria, viruses, or toxins

-b. Metabolic - such as glycogen breakdown

-c. Tissue degradation - useless tissue; web between fingers in embryos

-d. Maintenance – gets rid of old worn out organelles

-e. Autolysis – suicide sac; oxygen deprivation; membrane ruptures; cell destruction

Peroxisomes

1. Peroxisomes - membranous sacs, detoxifying enzymes

2. Exogenous substances - such as alcohol and formaldehyde

3. Free radicals – hydroxyl, O₂^- ; hydrogen peroxide, water; metabolic by products

4. Detoxification – organs such as liver and kidney; many

5. Self replicating - by pinching off of existing peroxisomes

Cytoskeleton

1. Cytoskeleton - support structures and generate various cell movements

2. Microtubules - largest, hollow tubes

-a. Tubulin - spherical protein subunits

-b. Centrosome (cell center) - microtubules originate from region near the nucleus

-c. Function – shape of cell and movement of cellular organelles

3. Microfilaments - smallest

-a. Actin - are thin strands made up of this contractile protein; like beaded necklace

-b. Function - changes in shape; movement; endocytosis, exocytosis

4. Intermediate filaments - intermediate size

-a. Function - stable and resist pulling forces in cell

-b. Structure - constructed like rope

Centrosomes and Centrioles

1. Centrosome - the microtuble point of origin has within it the centrioles

2. Centrioles - two small barrel shaped bodies lying at right angles to each other

-a. Microtubules – each barrel a hollow tube made up of 9 triplets of microtubule

-b. Mitotic spindles – form from these during cell division

-c. Motile projections - form the bases for cilia and flagella

Cilia and Flagella

1. Cilia - surfaces of cells; involved in the movement of materials (mucus)

2. Flagella - are longer and (in sperm) singular and move the cell itself

3. Development - centrioles multiply and line up under the membrane; cilia sprout

4. Structure - a pair of central microtubules and nine pairs of outer microtubules

NUCLEUS

Nucleus

1. Control center - contains genes which are responsible for all cellular activity

2. Nuclear envelope - double membrane; two phospholipids bilayers

-a. Nuclear pore - fusing of these bilayers; much freer movement of materials

3. Nucleoli - dark staining bodies found in the nucleus

-a. Composition – RNA and protein; no membrane

-b. Number - at least one, sometimes two or more

-c. Function - ribosomes are synthesized here

4. Chromatin - lightly stained thread like contains DNA

-a. Histones - globular proteins found in the chromatin; associated with DNA

-b. Nucleosome - fundamental unit of chromatin; 8 histones connected by DNA

5. Chromosomes - bar like; condensation of chromatin; mitosis; prevents breakage

CELL CYCLE

Interphase

1. Interphase – cells grows, DNA replicates

2. G1 (gap 1) - rapid growth and protein synthesis

-a. Variable - days or hours to months and years depending the type of cell

3. S (synthesis) phase - DNA replicates and new histones are synthesized

4. G2 (gap 2) - very brief; enzymes, other proteins for cell division, synthesized

-a. Centrioles – are doubled; two pairs

-b. Asters – microtubule arrays begin to extend from centrosome

DNA replication

1. Importance - duplication of genetic material for two new daughter cells

2. Helix untwist - hydrogen bonds broken between complementary strands of DNA

3. Template - each strand serves as a template

4. Nucleotides - building block; match up with complementary base on strand

-a. AT -adenine to thymine

-b. GC - guanine to cytosine

Mitosis

1. Prophase - begins when chromatin condense to form chromosomes

-a. Nuclear envelope – disappears

-b. Nucleolus - disappears

-c. Centrioles - move to opposite poles of the cell

-d. Mitotic spindles – microtubule, centrioles, across the middle; to centromere

-e. Chromatin – condenses to form chromosomes

-f. Chromosomes – made up of two sister chromatid

-g. Chromotid – of each chromosome carries identical info

-h. Centromere – region where sister chromatid are held together

2. Metaphase - chromosomes aligned, equator; from pulling of mitotic spindles

3. Anaphase - sister chromatid pulled apart, centromere, mitotic spindles; opposite

4. Telophase - prophase in reverse

-a. Nuclear envelope - reappear (from rough ER)

-b. Nucleolus - reappear

-c. Chromatin - chromosomes unwind

-d. Cytokinesis - begins

5. Cytokinesis - division of the cytoplasm

-a. Cleavage furrow - middle, cell deepens; contractile ring of microfilaments

PROTEIN SYNTHESIS

General

1. Gene - the segment of DNA which codes for a particular

2. Triplet - on the nucleotide sequence 3 nucleotides code for one amino acid

3. Exons - amino acid coding regions of a gene

4. Introns - non coding sequences of nucleotides

5. Uracil - replaces thymine on all forms of RNA

Transcription

1. Transcription - transfer info; DNA base sequence → mRNA base sequence

2. DNA uncoils - exposing the nucleotide sequence to be transcribed; template

3. mRNA - is synthesized

-a. Codon - 3 nucleotides on the mRNA; correspond to the triplet on the DNA

-b. Genetic code - codons of the mRNA correspond to particular amino acids

-c. Editing mRNA - enzymes remove the sequences of nucleotides coded by introns

Translation

1. Translation – nucleotide sequence translated into amino acid sequence

2. Ribosomes - the mRNA leaves the nucleus and binds to a ribosome

-a. rRNA - mRNA to complementary bases on rRNA makes up part of the ribosome

3. tRNA - has two sides; a head and a tail

4. Tail - a particular type of tRNA will bind to a particular amino acid in this region

5. Head – region that matches up with the codon of mRNA

-a. Anticodon - three nucleotides complementary to the codon of the mRNA

6. Amino acids – will be joined in a sequence which is specified by mRNA; DNA