Biology Midterm

chapter 4-6

Cell Theory

All organisms are made of cells.

All existing cells are produced by other living cells.

The cell is the most basic unit of life.

Prokaryotic Cell

Cells that do NOT have a nucleus or membrane-bound organelles (e.g., Bacteria).

Eukaryotic Cell

Cells that HAVE a nucleus and membrane-bound organelles (e.g., Plant & Animal cells).

Prokaryotes vs Eukaryotes Difference

Prokaryotes lack a nucleus and membrane-bound organelles; Eukaryotes have both.

Cytoskeleton

A network of proteins that supports cell shape, positions organelles, and assists in cell division.

Nucleus

Storehouse for genetic information (DNA) in eukaryotic cells.

Ribosomes

Organelles that link amino acids together to make proteins.

Endoplasmic Reticulum (ER)

An interconnected network of thin folded membranes that produces and processes proteins and lipids.

Golgi Apparatus

Organelle that modifies, packages, and sorts proteins for delivery to targeted destinations.

Vesicles

Small membrane-bound sacs that isolate and transport materials within the cell.

Mitochondria

Powerhouse of the cell that supplies energy (ATP) through cellular respiration.

Vacuole

A fluid-filled sac used for the storage of materials needed by a cell (very large central vacuole in plant cells).

Lysosome

Organelle containing digestive enzymes to break down waste, foreign materials, and worn-out cell parts in animal cells.

Centrioles

Cylinder-shaped organelles made of short microtubules that help divide DNA during cell division in animal cells.

Cell Wall

A rigid layer that gives protection, support, and shape to plant, algae, and fungal cells.

Chloroplast

Organelle in plant cells that converts solar energy into chemical energy through photosynthesis.

Organelles unique to Plant Cells

Cell wall, Chloroplasts, and a large Central Vacuole.

Organelles unique to Animal Cells

Lysosomes and Centrioles/Centrosomes.

Phospholipid Bilayer Structure

Polar hydrophilic head (phosphate + glycerol) on the outside, nonpolar hydrophobic tail (fatty acids) on the inside.

Fluid Mosaic Model

Model describing the cell membrane structure as flexible with embedded molecules (proteins, cholesterol, carbohydrates).

Role of Cholesterol in Cell Membrane

Strengthens and stabilizes the cell membrane structure.

Role of Carbohydrates in Cell Membrane

Acts as identification tags for cell recognition.

Selective Permeability

Property of the cell membrane that allows only certain materials to pass across it.

Membrane Receptor vs Intracellular Receptor

Membrane receptors bind ligands outside that CANNOT cross the membrane; Intracellular receptors bind ligands inside that CAN cross the membrane.

ATP (Adenosine Triphosphate)

High-energy molecule that transfers energy from the breakdown of food molecules to cell processes.

ADP (Adenosine Diphosphate)

Lower-energy molecule that can be converted into ATP by the addition of a phosphate group.

How ATP releases energy

Energy is released when the third phosphate group is removed from ATP, converting it to ADP.

Photosynthesis Overall Function

Process that captures energy from sunlight to make sugars (glucose) that store chemical energy.

Photosynthesis Equation

6CO2 + 6H2O + Light Energy -> C6H12O6 + 6O2

Chlorophyll

A molecule in chloroplasts that absorbs light energy (mainly blue/red light) for photosynthesis.

Thylakoid

Coin-shaped, membrane-enclosed compartments inside chloroplasts where light-dependent reactions occur.

Stroma

The fluid that surrounds the thylakoids inside a chloroplast where light-independent reactions (Calvin cycle) occur.

Light-Dependent Reactions Location & Output

Takes place in THYLAKOIDS; uses sunlight and H2O to produce O2, ATP, and NADPH.

Light-Independent Reactions (Calvin Cycle) Location & Output

Takes place in STROMA; uses CO2 and ATP/NADPH to produce glucose (sugar).

Cellular Respiration Overall Function

Process that releases chemical energy from sugars and other carbon-based molecules to make ATP when oxygen is present.

Cellular Respiration Equation

C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP (Energy)

Aerobic Process vs Anaerobic Process

Aerobic requires oxygen (e.g., Cellular Respiration); Anaerobic does NOT require oxygen (e.g., Glycolysis, Fermentation).

Glycolysis Location & Output

Occurs in the CYTOPLASM (Anaerobic); splits 1 glucose into two 3-carbon molecules, producing 2 net ATP.

Krebs Cycle Location & Output

Occurs in the MITOCHONDRIAL MATRIX (Aerobic); breaks down carbon molecules to produce CO2, ATP, NADH, and FADH2.

Electron Transport Chain (ETC) Location & Output

Occurs in the INNER MITOCHONDRIAL MEMBRANE (Aerobic); uses electrons to produce large amounts of ATP (~32-34) and H2O.

Fermentation Function

An anaerobic process that allows glycolysis to continue making ATP by recycling NAD+ when oxygen is not present.

Lactic Acid Fermentation

Type of fermentation occurring in human muscle cells during strenuous exercise; produces lactic acid as a byproduct.

Alcoholic Fermentation

Type of fermentation occurring in yeast; produces ethyl alcohol and CO2 as byproducts.

Chromosome

One long continuous thread of DNA that consists of numerous genes along with regulatory information.

Histones

Group of proteins that DNA wraps around to condense into chromatin.

Chromatin

The loose combination of DNA and proteins present during interphase before cell division.

Chromatid (Sister Chromatids)

One half of a duplicated chromosome; sister chromatids are identical copies joined together.

Centromere

Region of a condensed chromosome that holds together the two sister chromatids.

Telomere

Structures at the ends of DNA molecules that prevent chromosomes from sticking to each other and prevent gene loss.

Interphase

The phase where the cell grows, carries out normal functions, and copies its DNA before division (G1, S, G2).

Mitosis (PMAT) Overall Function

Division of the cell nucleus and its contents into two genetically identical nuclei.

Prophase (Mitosis Phase 1)

Chromatin condenses into tightly coiled chromosomes, nuclear envelope breaks down, and spindle fibers form.

Metaphase (Mitosis Phase 2)

Chromosomes align along the cell equator (middle) attached to spindle fibers.

Anaphase (Mitosis Phase 3)

Sister chromatids separate and are pulled to opposite sides of the cell by spindle fibers.

Telophase (Mitosis Phase 4)

Nuclear membranes start to form around chromosomes at each pole, chromosomes uncoil, and spindle fibers fall apart.

Cytokinesis

Division of the cell cytoplasm resulting in two genetically identical daughter cells.

Cytokinesis in Animal Cells vs Plant Cells

Animal cells pinch inward (cleavage furrow); Plant cells form a cell plate down the center due to the rigid cell wall.

Somatic cell

Cell that makes up all of the body tissues and organs, except gametes (body cells, diploid 2n = 46 chromosomes).

Gamete

Sex cell; an egg or a sperm cell (haploid n = 23 chromosomes).

Germ cells location and function

Located in ovaries and testes; develop into gametes (egg and sperm).

Homologous chromosomes

Chromosomes that have the same length, appearance, and copies of genes, although the alleles may differ.

Autosome

Chromosome that contains genes for characteristics not directly related to the sex of the organism (Pairs 1-22).

Sex chromosome

Chromosome that directly controls the development of sexual characteristics (X and Y chromosomes).

Diploid (2n) vs Haploid (n)

Diploid cells have two copies of every chromosome (body cells); Haploid cells have one copy of every chromosome (gametes).

Gametes Chromosome Count

22 autosomes and 1 sex chromosome (total 23 chromosomes).

Fertilization

Fusion of an egg and sperm cell in sexual reproduction.

Mitosis vs Meiosis Cell Types Produced

Mitosis makes more diploid cells; Meiosis makes haploid cells from diploid cells.

Meiosis Division Overview

During meiosis, diploid cells undergo two cell divisions (Meiosis I and Meiosis II) that result in haploid cells.

Meiosis I Key Event

Pairs of homologous chromosomes separate in four phases; reduces chromosome number.

Meiosis II Key Event

Sister chromatids divide in four phases; similar to mitosis, no DNA replication between Meiosis I and II.

Gametogenesis

Process by which gametes are produced through the combination of meiosis and other maturational changes.

Sperm

Male gamete; becomes streamlined and motile, primarily contributes DNA to an embryo.

Egg

Female gamete; contributes DNA, cytoplasm, and organelles to an embryo (gets most cell contents during meiosis).

Polar body

Haploid cell produced during female meiosis that has little more than DNA and eventually disintegrates.