chemical and cellular levels of organization

Phospholipids

A phosphate group linked to a diglyceride and nonphosphate group

An integral unity of the plasma and membrane of a cell

Proteins

Chains of amino acids; account for approximately 20% of total body weight

Phospholipids

A phosphate group linked to a diglyceride and nonphosphate group

An integral unity of the plasma and membrane of a cell

Proteins

Chains of amino acids; account for approximately 20% of total body weight

Protein functions

1. Support

2. Movement

3. Transport

4. Buffer

5. Metabolic regulation

6. Coordination and control

7. Defense

Protein structure

Amino acids are held together via peptide bonds, resulting in peptides

Peptide chains form together, resulting in polypeptides (proteins)

Primary structure

Sequence of an amino acid along a polypeptide

Secondary structure

Results due to hydrogen bonding; produces a simple spiral (alpha helix), or a more flat configuration (beta pleated sheet)

Tertiary structure

3D folding of a protein due to very strong disulfide bonds

Quaternary structure

Due to the aggregation or combination of several polypeptide chains

Activation energy

An amount of energy required to start a reaction

Enzymes

Promote chemical reactions by lowering activation energy requirements; belong to the class, catalysts

Catalysts

Compound that accelerates a chemical reaction without being permanently changed or consumed

Enzyme functions

1. Specificity

2. Saturation limit

3. Regulation

Specificity

The active site of an enzyme is meant to bind only to a substrate that has a particular shape and charge; enzymes that differ slightly but catalyze the same reactions are known as isoenzymes

Saturation limit

Enzymes have a maximum rate they can catalyze a reaction (saturation limit)

Regulation

Other molecules or ions may turn an enzyme “on” of “off” by changing conformational shape

Nuclei acids

Large, organic molecules composed of carbon, hydrogen, nitrogen, and phosphorus

Deoxyribonucleic acid (DNA)

• stores the info concerning inherited characteristics

• Found in the nucleolus of a cell

Ribonucleic acid (RNA)

• used for an assortment of cellular functions involving the production of proteins

Five nitrogenous bases

Adenine (A)

Guanine (G)

Cytosine (C)

Thymine (T)

Uracil (U)

DNA complementary base pairs

Adenine-Thymine (A-T)

Cytosine-Guanine (C-G)

Types of RNA

1. Messenger RNA (mRNA)

2. Transfer RNA (tRNA)

3. Ribosomal (rRNA)

(RNA is single stranded molecule)

adenosine triphosphate (ATP)

the most important and widely used energy source in human cells

Made from adenosine diphosphate via the following reaction

ADP + phosphate group + energy —> ATP + H2O

Sex cells (germ cells)

Sperm in males; oocytes in females

Somatic cells

All other cell types in the body

Plasma membrane (cell membrane)

The general name for the outer boundary of the cell; responsible for separating what is extracellular and what is intracellular

Functions of plasma membrane

1. Physical isolation

2. Regulation of exchange

3. Sensitivity to environment

4. Structural support

Phospholipid bilayer

Accounts for the vast majority of the surface area of the plasma membrane

Cholesterol

Also a commonly imbedded in the phospholipid bilayer

Integral proteins (transmembrane proteins)

Part of the membrane structure; span the entire width of the membrane

Peripheral proteins

Bound to either one side or the other of a membrane; can be easily separated from the membrane

Anchoring proteins

Keep portion of the cell membrane in position

Recognition proteins

Contact and identify other molecules or cells

Enzymes

Catalyze reactions

Receptor proteins

Sensitive to extracellular molecules called ligands, which trigger a change in the cell

Carrier proteins

Bind solutes and carry them across the plasma membrane

Channels

form a passageways across the entire plasma membrane

Cytosol

contains dissolved nutrients, ions, soluble and insoluble proteins, and waste products

Differences between cytosol and extracellular fluid

1. Potassium concentrations are high intracellularly, low extracellularly

2. Sodium concentrations are high intracellularly, low extracellularly

3. There are a large amount of suspended proteins in cytosol

4. Reserves of carbohydrate, amino acids, and lipids can be found in the cytosol

Inclusions

Insloluble materials found in the cytosol

Organelles

small distinct portions of a cell that perform certain functions; many are structures suspended within cytosol

Non-membranous organelles

• cytoskeleton

• Microvilli

• Centrioles

• Cilia

• Ribosomes

• Proteasomes

Membranous organelles

• endoplasmic reticulum

• Golgi apparatus

• Lysosomes

• Perixidomes

• Mitochondria

• Nucleus

Cytoskeleton

The functional skeleton of the cell

Composed of

1. Microfilaments

2. Intermediate filaments

3. Microtubules

Microvilli

Small, finger like projections of the plasma membrane, which greatly increases the surface area of a cell

Numerous in the GI tract as they aid in digestion

Centrioles

A pair of arranged microtubules that assist in the movement of chromosomes during cell division

Endoplasmic reticulum

Network of intracellular membranes connected to the nuclear envelope of the nucleus

Functions

1. Synthesis

2. Storage

3. Transport

4. Detoxification

Smooth ER

ER that is not associated with ribosomes

Rough ER

ER that is associated with ribosomes

Often, sends transport vesicles to the Golgi apparatus

Golgi apparatus

5-6 flattened membranous discs

Functions

1. Modifies and packages secretions, such as hormones and enzymes

2. Renews of modifies the plasma membrane

3. Packages special enzymes in vesicles for use in the cytoplasm

Lysosomes

Vesicles that provide an isolated environment for potentially dangerous chemical reactions

Functions

1. Fuse with and break down damaged organelles

2. Fuse with endoscopes and break down materials from outside of a cell

3. Break into parts during cell death, releasing enzymes into the cytoplasm

Peroxisomes

Smaller vesicles that carry a different set of enzymes than lysosomes; don’t arise from the Golgi apparatus

Arise by budding off of existing perioxomes

Mitochondria

Organelles responsible for ATP production

Have two membranes

1. Outer mitochondrial membrane

2. Inner mitochondrial membrane

The matrix is the innermost area of a mitochondria, with the space in between the two membranes being known as the intermembrane space

Nucleus

Largest organelle; contains the genetic info of a cell

Most only have one but others have many nuclei

Nuclear envelope

Double layered membrane that separates the nucleus from the cytosol

The space between the membranes is known as the pernuclear space

Nuclear pores

Allow communication between the nucleus and the cytoplasm

Gene

The functional unit of heredity

Transcription

The process of synthesizing a messenger RNA (mRNA) template from DNA

Important because DNA cannot leave the nucleus of a cell

Template strand

Used for mRNA production

Coding strand

Contain the complementary pairs of the template strand

Permeability

Property of a membrane that determines which substances can pass through that membrane

The plasma membrane is said to be selectively permeable

Diffusion

The movement of a substance from an area of higher concentration to an area of lower concentration

Concentration gradient

The difference between a high and low concentration

Rate of diffusion is dependent on…

1. Distance

2. Molecule size

3. Concentration gradient

4. Temp

5. Electrical forces

Simple diffusion

A substance diffuses through the lipid portion of a membrane

Molecule must be

1. Small

2. Uncharged

3. Hydrophobic

Facilitated diffusion

A substance diffuses through a membrane via a transmembrane protein (a channel or carrier)

Primary active transport

Additional energy is used at the membrane to move a substance against its concentration gradient

Sodium potassium pump

Actively moves one substance in one direction and another substance in the opposite direction

The sodium potassium pump moves…

Three sodium ions extracellularly and two potassium ions intracellularly using one molecule of ATP

Secondary active transport

Uses primary active transport to indirectly move a substance against its concentration gradient

Osmosis

The movement of water across a membrane from an era of lower to higher solute concentration

Vesicular transport

The movement of materials into or out of a cell via vesicles

Endocytosis

Extracellular substances brought into a cell via a vesicle

Pinocytosis

Endocytosis in which the vesicle is bringing in extracellular fluid

Exocytosis

Vesicular fusion of a vesicle to a target membrane

Phagocytosis

Produces a phagosome, which surrounds and engulfs and objects, typically a very large one

Potential difference

Exists when a positive charge and negative charge are held apart from one another

Transmembrane potential

A potential difference across a plasma membrane

Resting potential

The transmembrane potential of an undisturbed resting cell

Stem cells

Undifferentiated cells that can divide onto more stem cells or differentiate into other types of cells

Differentiation

The change into a more specialized type of cell

Cancer

Illness character used by mutations that disrupt normal control mechanisms in the human body; typically associated with malignant cells

Tumor (neoplasm)

Mass produced by abnormal cell growth an division; may be benign or malignant

A malignant tumor is able to invade surrounding tissue and metastasizes

Metastasis

The distant traveling of malignant cells to other organs or tissue