Cell Structure and Function Overview

Nucleus

The nucleus has a double membrane with pores. It stores DNA, makes RNA, and helps build parts of ribosomes.

Rough ER

The Rough ER has membranes with ribosomes attached. It makes proteins and helps transport them within the cell.

Smooth ER

The Smooth ER is made of folded tubes without ribosomes. It makes lipids, stores calcium, and helps detoxify the cell.

Golgi Complex

The Golgi Complex is made of stacked membranes. It folds, modifies, and packages proteins to send them where they are needed.

Ribosomes

Ribosomes are made of RNA and proteins. They build proteins and can float freely or attach to the Rough ER.

Mitochondria

Mitochondria have a double membrane. They make energy (ATP) by breaking down food during cellular respiration.

Lysosomes

Lysosomes are sacs filled with enzymes. They break down waste, old cell parts, and even help with programmed cell death (apoptosis).

Vacuoles

Vacuoles are membrane-bound sacs. They store water, nutrients, or waste and help keep plant cells firm by maintaining pressure.

Chloroplasts

Chloroplasts have a double outer membrane. They capture sunlight and use it to make food (glucose) through photosynthesis.

Surface Area to Volume Ratio

Smaller cells have more surface area compared to their volume, which helps them move materials in and out faster and more efficiently.

Plasma Membrane

The plasma membrane is made of phospholipids, proteins, carbohydrates, and cholesterol. It controls what enters and leaves the cell.

Simple Diffusion

In simple diffusion, small nonpolar molecules like oxygen move directly across the membrane without using energy.

Facilitated Diffusion

In facilitated diffusion, molecules move across the membrane with help from proteins. No energy is needed.

Active Transport

In active transport, molecules move against their concentration gradient using energy (ATP) and special proteins.

Bulk Transport

Bulk transport moves large materials. Endocytosis brings materials into the cell. Exocytosis sends materials out of the cell.

Isotonic Solution

In an isotonic solution, water moves equally in and out of the cell, and the cell stays the same size.

Hypertonic Solution

In a hypertonic solution, water leaves the cell, causing the cell to shrink.

Hypotonic Solution

In a hypotonic solution, water enters the cell, causing the cell to swell.

Hypotonic solution

A solution where water enters the cell, causing the cell to swell and possibly burst.

Polar water

Water is polar due to polar covalent bonds between oxygen and hydrogen within a molecule and hydrogen bonds between water molecules.

Cohesion

Water molecules attracted to other water molecules.

Adhesion

Water molecules attracted to other polar substances.

Capillary action

The movement of water (or other liquids) against gravity through narrow spaces like plant roots.

Universal solvent

Water can dissolve many substances due to its polarity, binding to both positive and negative ions.

Surface tension

Cohesion from hydrogen bonding forms a surface layer.

Example of surface tension

Skipping rocks or water striders walking on water.

Ice density

Ice is less dense than liquid water because hydrogen bonds inhibit compaction, making ice float.

Role of ice in the environment

Acts as a temperature buffer.

High specific heat in water

Water must absorb or release a large amount of energy to change 1°C in 1g of water.

Evaporative cooling

Water on an organism's surface absorbs heat energy and cools the organism as bonds break.

Water's high specific heat environmental benefit

It buffers temperatures in coastal regions and stabilizes body temperature.

pH formula

pH = -log [H⁺].

pH and hydrogen ion concentration

As hydrogen ion concentration increases, the pH decreases.

Elements in carbohydrates

Carbon (C), Hydrogen (H), and Oxygen (O) in a 1:2:1 ratio.

Monomer of carbohydrates

Monosaccharide.

Examples of carbohydrates

Glucose, Fructose, Galactose.

Bond between two monosaccharides

Glycosidic linkage.

Storage form of carbohydrates

Starch in plants, Glycogen in animals.

Cellulose

A structural carbohydrate found in plant cell walls.

Elements in proteins

Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), and sometimes Sulfur (S).

Monomer of proteins

Amino acid.

Bond linking amino acids

Peptide bond.

Levels of protein structure

Primary (peptide bonds), Secondary (hydrogen bonds, alpha helix or beta sheet), Tertiary (bonds between R groups), Quaternary (bonds between polypeptides).

Elements in nucleic acids

Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), and Phosphorus (P).

Monomer of nucleic acids

Nucleotide.

Parts of a nucleotide

Phosphate group, Pentose sugar, Nitrogenous base.

Nitrogenous bases in DNA

A, T, C, G.

Nitrogenous bases in RNA

A, U, C, G.

DNA strand orientation

5' to 3' direction; antiparallel.

Elements in lipids

Carbon (C), Hydrogen (H), Oxygen (O), and sometimes Phosphorus (P) in phospholipids.

Lipids polarity

Nonpolar.

Parts of a fat molecule

Glycerol and three fatty acids.

Saturated vs unsaturated fatty acids

Saturated fatty acids have no double bonds (fully saturated with hydrogen); unsaturated fatty acids have at least one double bond.

Phospholipids

Lipids with a hydrophilic head and hydrophobic tail, forming cell membranes.

Steroids composition

Composed of four fused rings.

Function of steroids

Acting as ligands for intracellular receptors.