Cell Structure and Function Overview

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

Nucleus

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

Rough ER

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

Smooth ER

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

Golgi Complex

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

Ribosomes

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

Mitochondria

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

Lysosomes

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

Vacuoles

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

Chloroplasts

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

Surface Area to Volume Ratio

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

Plasma Membrane

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

Simple Diffusion

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

Facilitated Diffusion

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

Active Transport

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

Bulk Transport

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

Isotonic Solution

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

Hypertonic 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.

Hypotonic solution

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

Polar water

Water molecules attracted to other water molecules.

Cohesion

Water molecules attracted to other polar substances.

Adhesion

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

Capillary action

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

Universal solvent

Cohesion from hydrogen bonding forms a surface layer.

Surface tension

Skipping rocks or water striders walking on water.

Example of surface tension

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

Ice density

Acts as a temperature buffer.

Role of ice in the environment

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

High specific heat in water

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

Evaporative cooling

It buffers temperatures in coastal regions and stabilizes body temperature.

Water's high specific heat environmental benefit

pH = -log [H⁺].

pH formula

As hydrogen ion concentration increases, the pH decreases.

pH and hydrogen ion concentration

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

Elements in carbohydrates

Monosaccharide.

Monomer of carbohydrates

Glucose, Fructose, Galactose.

Examples of carbohydrates

Glycosidic linkage.

Bond between two monosaccharides

Starch in plants, Glycogen in animals.

Storage form of carbohydrates

A structural carbohydrate found in plant cell walls.

Cellulose

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

Elements in proteins

Amino acid.

Monomer of proteins

Peptide bond.

Bond linking amino acids

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

Levels of protein structure

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

Elements in nucleic acids

Nucleotide.

Monomer of nucleic acids

Phosphate group, Pentose sugar, Nitrogenous base.

Parts of a nucleotide

A, T, C, G.

Nitrogenous bases in DNA

A, U, C, G.

Nitrogenous bases in RNA

5' to 3' direction; antiparallel.

DNA strand orientation

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

Elements in lipids

Nonpolar.

Lipids polarity

Glycerol and three fatty acids.

Parts of a fat molecule

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

Saturated vs unsaturated fatty acids

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

Phospholipids

Composed of four fused rings.

Steroids composition

Acting as ligands for intracellular receptors.

Function of steroids