Biology: Cell Structure, Macromolecules, and Genetics Overview

Biology

The study of life and living organisms.

Living things use energy

All living organisms require energy to perform activities and maintain life processes.

Living things grow and develop

Organisms increase in size and undergo changes throughout their life cycle.

Living things maintain themselves

Organisms regulate internal conditions to stay stable (homeostasis).

Living things reproduce

Living organisms can produce offspring to pass on genetic information.

Living things respond to stimuli

Organisms react to changes in their environment.

Big idea of biology

All living organisms are made of cells.

Examples of organisms made of cells

Bacteria, fungi, plants, animals, and more.

Cells are made of "stuff"

Cells contain elements that bond to form molecules.

Macromolecules

Large biological molecules: carbohydrates, proteins, lipids, nucleic acids.

25 elements in the human body

The human body contains about 25 essential elements.

Monosaccharides

Carbohydrates made of one sugar subunit; provide quick energy.

Disaccharides

Carbohydrates made of two sugar subunits.

Polysaccharides

Carbohydrates made of many sugar subunits; provide structure and long‑lasting energy.

Cellulose

Most abundant organic compound on Earth; forms fibrils in plants.

Cellulose structure

Polymer of glucose arranged in parallel chains.

Cellulose digestibility

Most animals cannot hydrolyze cellulose.

Insoluble fiber

Cellulose scrapes digestive tract walls and aids digestion.

Cellulose‑digesting bacteria

Found in organisms like termites.

Chitin

Structural polysaccharide in insect and crustacean exoskeletons.

Chitin in fungi

Also found in fungal cell walls.

Lipids contain C, H, O

Lipids are made of carbon, hydrogen, and oxygen.

Lipids store more energy than carbs

Lipids contain more stored energy per gram.

Lipid functions

Cushion organs and insulate the body.

Lipids defined by physical properties

Lipids are hydrophobic and do not mix with water.

Hydrophobic vs hydrophilic

Lipids are hydrophobic (water‑fearing).

Saturated fats

Solid at room temperature; mostly from animals.

Unsaturated fats

Liquid at room temperature; mostly from plants.

Plant fats

Mostly unsaturated.

Animal fats

Mostly saturated.

Plaques

Lipid deposits that build up in blood vessels.

Sterols

Lipids that regulate growth and development.

Proteins

Polymers of amino acids; chief building blocks of life.

Protein structure

Unique 3D shapes that determine function.

Enzymes

Proteins that speed up chemical reactions.

Enzymes lower activation energy

They increase reaction rate without being consumed.

Nucleic acids

DNA and RNA; store and transmit genetic information.

Two types of nucleic acids

DNA and RNA.

Nucleic acid function

Direct protein production and determine inherited traits.

DNA structure

Double helix with two spiraling strands.

DNA hydrogen bonds

Bases are connected by hydrogen bonds.

Base pairing rules

A pairs with T; G pairs with C.

Human genome project

Uses one DNA strand for sequencing.

Human genome size

About 3 billion base pairs.

RNA sugar

Ribose with an extra oxygen atom.

RNA base difference

Uses uracil (U) instead of thymine (T).

RNA structure

Single‑stranded molecule.

Cell

The smallest unit of life.

Unicellular organism

Made of one cell.

Multicellular organism

Made of many cells working together.

Tissues

Groups of similar cells performing shared functions.

Organs

Structures made of multiple tissues.

Organ system

Group of organs performing major body functions.

Two categories of cells

Prokaryotes and eukaryotes.

Prokaryotes include

Bacteria and archaea.

Eukaryotes include

Animals, plants, fungi, protists.

Anton van Leeuwenhoek

Observed bacteria and protists; called them "animalcules."

Robert Hooke

Coined the term "cell" after observing cork.

1830s discovery

All plants and animals are made of cells.

Schleiden and Schwann

Developed cell theory.

Cell theory part 1

All living things are composed of cells.

Cell theory part 2

Cells arise from preexisting cells.

Exception to cell theory

First cell came from free‑floating molecules 3.5 billion years ago.

Plasma membrane

Boundary that encloses every cell.

Chromosomes

Structures carrying genes made of DNA.

Ribosomes

Structures that make proteins.

Cytoplasm

Jelly‑like interior of the cell.

Two types of cells

Prokaryotic and eukaryotic.

Cytoplasm location

Between plasma membrane and nuclear membrane.

Cytoplasm composition

Organelles suspended in cytosol.

Cytoplasm water content

70-80% water.

Phospholipid movement

Not locked in place; float within bilayer.

Membrane components

Some components are loosely anchored.

Hydrophobic tails

Push away from water and prevent leaking.

Membrane purpose

Forms boundary and controls movement of substances.

Transmembrane proteins

Span the entire lipid bilayer.

Surface proteins

Located on inner or outer membrane surface.

Diffusion

Solute moves from high to low concentration.

Concentration gradient

Molecules move down their gradient.

Simple diffusion

Small, uncharged molecules pass directly through membrane.

Most molecules cannot pass freely

Polar molecules need assistance.

Facilitated diffusion

Transport proteins help molecules cross membrane.

Osmosis

Diffusion of water across a membrane.

Water movement

From high water concentration to low water concentration.

Purpose of osmosis

Equalizes water concentration inside and outside the cell.

Hydrophobic bilayer effect

Limits water flow.

Aquaporins

Water channel proteins that allow water to pass.

Tonicity

Comparison of solute concentrations inside vs outside the cell.

Osmosis direction

Determined by total solute concentration.

First cells on Earth

Appeared 3.5 billion years ago.

Prokaryotes are unicellular

Made of one cell.

Prokaryote size

1-10 µm.

Two groups of prokaryotes

Bacteria and archaea.

Bacteria

Largest group of prokaryotes.

Archaea

Live in extreme environments.

Four prokaryotic features

Plasma membrane, cytoplasm, ribosomes, DNA.

Nucleoid

Region where prokaryotic DNA is located.

Bacterial cell wall

Made of peptidoglycan.

Cell wall function

Protection and prevents dehydration.

Gram‑positive vs Gram‑negative

Two major bacterial cell wall types.