Organelles and Cell Life Cycles

Cells

Definition: Basic unit of life

• Functions: carry out life processes, provide structure, reproduce, respond to environment

• Comes in all shapes and sizes

• Key Structures:

  • Nucleus: DNA/control center

  • Mitochondria: energy (ATP)

  • Ribosomes: protein production

  • Cell membrane: protection & transport

  • Cytoplasm: holds organelles

• Examples: animal cells, plant cells, bacterial cells

💡 = tiny factories keeping the body alive

True or false? Structure determines function

True! Structure → Function

• Concept: the shape or structure of a cell or organelle helps it do its job.

• Examples:

  • Mitochondria: folded inner membrane → more surface area → makes more ATP

  • Ribosomes: small & round → efficiently make proteins

  • Cell membrane: flexible & selectively permeable → controls what enters/exits

💡 Quick tip: How it’s built determines what it can do!

Organelle

• Definition: tiny “mini-organs” inside a cell that do specific jobs

• Functions / Examples:

  • Nucleus: control center, holds DNA

  • Mitochondria: makes energy (ATP)

  • Ribosomes: make proteins

  • Endoplasmic Reticulum (ER): transports & folds proteins/lipids

  • Golgi Apparatus: packages & ships proteins

  • Lysosomes: breaks down waste

  • Cell membrane: protects cell & controls entry/exit

• Importance: each organelle’s structure is related to its function → keeps cell alive

💡 tiny factories inside the cell, each with a job

Plasma Membrane

• Definition: outer layer of the cell that separates inside from outside

• Structure: phospholipid bilayer with hydrophilic heads & hydrophobic tails, plus proteins

• Functions:

  • Controls what enters/exits the cell (selectively permeable)

  • Protects the cell

  • Allows communication with other cells

• Importance: maintains homeostasis and cell survival

• Examples: cell membranes of all animal and plant cells

💡 = gatekeeper of the cell

Semipermeable (Selectively Permeable)

• Definition: allows some substances to pass through but blocks others

• Example / Situation:

  • A plasma membrane lets oxygen and water enter the cell to keep it alive but blocks bacteria or large toxins from coming in
    Importance / Function:

    • Controls what enters/exits the cell

    • Maintains homeostasis

  • Other info: usually allows small or nonpolar molecules (like oxygen, water) but blocks large or charged molecules

  💡 = selective gate for the cell

Phospholipids

• Definition / Structure: made of glycerol + 2 fatty acid tails (hydrophobic) + phosphate head (hydrophilic)

• Function / Importance:

  • Forms cell membranes (phospholipid bilayer)

  • Controls what enters/exits the cell

  • Protects the cell & keeps homeostasis

• Example / Situation: in a plasma membrane, heads face water, tails face inward → barrier forms to protect cell

💡 = building blocks of the cell membrane

Phospholipid - Hydrophilic and Hydrophobic

• Hydrophilic (“water-loving”): phosphate head → faces water (outside & inside the cell)

• Hydrophobic (“water-fearing”): fatty acid tails → face inward, away from water

• Function / Importance: this arrangement forms the phospholipid bilayer, controls what enters/exits the cell, protects the cell, maintains homeostasis

• Example / Situation: in a cell membrane, heads touch water inside/outside the cell, tails hide in the middle → forms a selective barrier

💡 Quick tip: Heads love water, tails hate water → bilayer barrier!

Saturated vs Unsatured Fatty Acids

• Saturated Fatty Acid:

  • Structure: no double bonds, straight chains

  • State at room temp: solid (butter, lard)

  • Health note: can raise cholesterol if eaten in excess

• Unsaturated Fatty Acid:

  • Structure: has ≥1 double bond, bent chains

  • State at room temp: liquid (olive oil, avocado, nuts)

  • Health note: generally healthier, can lower cholesterol

💡 Quick tip: Saturated = straight & solid, Unsaturated = bent & liquid

Membrane Proteins

• Definition: proteins embedded in the cell membrane

• Types / Functions:

  • Transport proteins: move substances in/out of cell

  • Receptor proteins: receive chemical signals

  • Enzymes: speed up chemical reactions at the membrane

  • Structural proteins: give support and shape to the cell

• Importance: help the cell communicate, transport, and maintain homeostasis

• Example / Situation: glucose enters the cell through a transport protein, hormones bind to receptor proteins

💡 = workers in the cell gate, delivery, and communication system

Passive Transport

• Definition: movement of substances across the cell membrane without using energy

• How it works / Types:

  • Simple Diffusion: molecules move from high → low concentration

  • Osmosis: diffusion of water

  • Facilitated diffusion: uses transport proteins to help molecules cross

• Importance / Function: balances concentrations inside/outside the cell → maintains homeostasis

• Example / Situation: oxygen enters a cell from blood, water moves in/out to balance cell volume

💡 = no energy needed, molecules go with the flow

Facilitated Diffusion

• Definition: passive transport of molecules with the help of transport proteins

• How it works: molecules move from high → low concentration using channel or carrier proteins

• Importance / Function: allows molecules that can’t pass through the lipid bilayer (like glucose or ions) to enter/exit the cell

• Example / Situation: glucose enters cells via a glucose transporter protein

💡 = “helped” passive transport

Osmosis

• Definition: diffusion of water across a semipermeable membrane

• How it works: water moves from high → low water concentration (or low → high solute concentration)

• Importance / Function: balances water inside/outside the cell → maintains homeostasis

• Example / Situation: plant roots absorb water from soil; water moves into red blood cells in the body

💡 = water moving to where it’s needed

Glycoprotein

• Definition: protein with a carbohydrate chain attached

• Location: cell membrane

• Function / Importance:

  • Acts as an ID tag so cells can recognize each other

  • Helps with cell communication

  • Plays a role in the immune system (recognizing friendly vs. foreign cells)

• Example / Situation: blood types (A, B, AB, O) are determined by specific glycoproteins on red blood cells

💡 = cell’s ID badge for recognition & communication

Glycolipid

• Definition: lipid with a carbohydrate chain attached

• Location: cell membrane

• Function / Importance:

  • Acts as a recognition marker (like glycoproteins)

  • Helps cells stick together

  • Maintains stability of the membrane

• Example / Situation: glycolipids on red blood cells help determine blood type and allow immune recognition

💡 = lipid + sugar → recognition & stability

Membrane Proteins – Process

• Transport proteins: move molecules in/out (ex: glucose channel)

• Receptor proteins: receive signals (ex: insulin receptor)

• Enzymes: speed up reactions

• Structural proteins: give support & connect cells
  💡 Quick tip: Membrane proteins = workers of the cell gate

Cytoplasm

• Definition: jelly-like fluid inside the cell that surrounds organelles

• Composition: mostly water + salts + proteins

• Function / Importance:

  • Holds organelles in place

  • Site of many chemical reactions (like glycolysis in cellular respiration)

  • Helps transport materials within the cell

  • Site of Anaerobic Respiration

  • Liquid portion is called Cytosol

• Example / Situation: like the “soup” where all the ingredients (organelles) float and reactions happen

💡 = the cell’s soup where reactions happen

Endoplasmic Reticulum

• Definition: network of folded membranes near the nucleus

• Types:

  • Rough ER: has ribosomes → makes & transports proteins

  • Smooth ER: no ribosomes → makes lipids, detoxifies, stores calcium

• Function / Importance: pathway for making, folding, and moving molecules in the cell

• Helps build essential molecules (proteins & lipids), moves them around, keeps the cell healthy.

• Where is it? Found in the cytoplasm, right next to the nucleus.

• Example / Situation: like a factory assembly line → Rough ER builds proteins, Smooth ER makes lipids & cleans toxins

💡 ER = cell’s factory → Rough = proteins, Smooth = lipids & detox

Rough ER

• What it is: Folded membranes in the cytoplasm, covered with ribosomes (looks rough)

• What it does: Makes, modifies & transports proteins; sends them out or to the membrane

• Importance: Essential for growth, repair, enzymes, hormones, transport

• Where: Cytoplasm of eukaryotic cells, abundant in protein-making cells

• Example: Pancreas cells → make insulin
  💡 = protein factory (ribosomes are the workers)

Smooth ER

• Definition: type of ER without ribosomes

• Functions / Importance:

  • Makes lipids → used for cell membranes

  • Detoxifies chemicals

  • Stores calcium for cell signaling

• Example / Situation: like a cell’s oil & cleaning department → produces fats for membranes and removes toxins

💡 = lipid factory → builds membranes + detox + calcium storage

Golgi Apparatus

• Definition: stack of flattened membranes in the cell

• Function / Importance:

  • Modifies, sorts, and packages proteins and lipids from the ER

  • Prepares molecules for transport inside/outside the cell

• Example / Situation: like a post office or shipping center → labels packages (proteins/lipids) and sends them to their destination

💡 = cell’s shipping & packaging center

Ribosomes

• Definition: small organelles that make proteins

• Location:

  • Free in cytoplasm: make proteins for the cell itself

  • Attached to Rough ER: make proteins for export or membranes

• Function / Importance:

  • Build proteins by linking amino acids together (protein synthesis)

  • Site of protein synthesis

• Example / Situation: like a cell’s kitchen, cooking up proteins needed for the cell or to send elsewhere

💡 = protein factories of the cell

Endocytosis

• Definition: process where the cell engulfs substances to bring them inside the cell

• How it works:

  • Cell membrane wraps around material → forms a vesicle → brings it into the cytoplasm

• Function / Importance: lets the cell take in nutrients, liquids, or large molecules

• Example / Situation: white blood cells engulf bacteria to fight infection; cells take in large nutrients

💡 = cell “eating” or “drinking” things

Exocytosis

• Definition: process where the cell releases substances to the outside

• How it works:

  • Vesicle containing molecules fuses with the cell membrane → contents are expelled

• Function / Importance: removes waste, sends out hormones or proteins

• Example / Situation: pancreas cells release insulin into the blood; neurons release neurotransmitters

💡 = cell “spitting out” or exporting things

Vesicles

• Definition: small membrane-bound sacs in cells

• Function / Importance:

  • Transport proteins, lipids, or waste within or out of the cell

  • Can store materials temporarily

• Example / Situation:

  • Carry proteins from Rough ER → Golgi Apparatus → cell membrane

  • Transport neurotransmitters in neurons

• Relation to Endo/Exocytosis: vesicles are the “packages” brought in or sent out

💡 = cell’s delivery trucks or packages

Phagocytosis

• Definition: type of endocytosis where the cell engulfs large particles or cells

• How it works: cell membrane wraps around a particle → forms a phagosome → particle is digested

• Function / Importance: allows the cell to eat bacteria, debris, or dead cells → important for immune defense

• Example / Situation: white blood cells engulf bacteria to fight infection

💡 = cell “eating” big stuff like bacteria

Pinocytosis

• Definition: type of endocytosis where the cell engulfs liquids or dissolved substances

• How it works: cell membrane folds inward → forms a vesicle → brings fluid into the cell

• Function / Importance: lets the cell take in nutrients or extracellular fluids

• Example / Situation: cells in the intestine absorb nutrients dissolved in water

💡= cell “drinking” liquids

Mitochondria

• Definition: double-membrane organelle known as the cell’s powerhouse

• Function / Importance:

  • Produces ATP (energy) through cellular respiration

  • Breaks down glucose and other nutrients to release energy

• Structure:

  • Outer membrane: protects organelle

  • Inner membrane (cristae): folded → more surface area for energy production

  • Matrix: fluid inside where reactions occur

• Example / Situation: muscle cells have many mitochondria → need lots of energy for movement

💡 = energy factory of the cell

Lysosomes

• Definition: small organelles containing digestive enzymes

• Function / Importance:

  • Surrounds and break down waste, damaged organelles, and foreign particles

  • Helps recycle materials for the cell

• Structure: membrane-bound sac

• Example / Situation: white blood cells use lysosomes to digest engulfed bacteria

💡 = cell’s recycling & cleanup crew

Nucleus

• Location: Inside the cytoplasm of the cell

• What it does:

  • Gives the cell shape & support

  • Moves organelles and vesicles

  • Helps the cell move/divide

  • (like a skeleton + highway for transport)

  • Overall framework of cells

  • Structures: Microtubules, microfilaments, intermediate filaments

  • Example: Moves vesicles around the cell like a conveyor belt

💡 = the cell’s skeleton + transport system inside the cytoplasm

Microfilaments

• Definition: thin protein fibers in the cytoskeleton made of actin

• Function / Importance:

  • Maintain cell shape

  • Part of Cytoskeleton + Smallest/thinnest fibers

  • Help with cell movement (like crawling or changing shape)

  • Assist in cytoplasm streaming and cell division

• Example / Situation: white blood cells use microfilaments to move toward infection sites

💡 = thin threads that shape the cell and help it move

Intermediate fibers

• Definition: medium-thickness protein fibers in the cytoskeleton

• Function / Importance:

  • Provide mechanical strength

  • Help maintain cell shape

  • Medium thickness fibers

  • Anchor organelles in place

• Example / Situation: skin cells have strong intermediate filaments to withstand stretching

💡 = sturdy ropes that support and stabilize the cell

Microtubules

• Definition: thick, hollow protein tubes in the cytoskeleton made of tubulin

• Function / Importance:

  • Maintain cell shape

  • Largest/thickest fibers

  • Act as tracks for organelle and vesicle movement

  • Form cilia, flagella, and spindle fibers during cell division

• Example / Situation: vesicles use microtubules like highways to reach different parts of the cell

💡 = cell’s highways + structural support

Cytoskelton structure

• Microfilaments: thin, flexible fibers → shape + movement (actin)

• Intermediate Filaments: medium thickness → strength + anchor organelles

• Microtubules: thick hollow tubes → shape, transport, cilia/flagella, cell division

💡 = framework of microfilaments + intermediate filaments + microtubules

Centrosome - (micrograph structure of this pictured below)

• Definition: region near the nucleus that organizes microtubules

• Function / Importance:

  • Controls microtubule growth

  • Forms spindle fibers during cell division

  • Helps maintain cell shape and structure

  • Plays important role in cell divison + can only be seen during CD

  • General location of this is idenitifed by the centrioles

• Example / Situation: during mitosis, centrosomes pull chromosomes apart using spindle fibers

💡 Quick tip: Centrosome = cell’s microtubule organizer & division helper

Centrioles

• Definition: cylindrical structures made of microtubules

• Location: found in the centrosome

• Function / Importance:

  • Help organize spindle fibers during cell division

  • Assist in forming cilia and flagella

• Example / Situation: during mitosis, centrioles help pull chromosomes apart

💡 = cell’s spindle organizers + cilia/flagella helpers

Cell extension

• Definition: structures that stick out from the cell surface to help with movement or sensing

• Types:

  • Cilia → short, hair-like, move substances across cell surface (ex: in respiratory tract)

  • Flagella → long, tail-like, move the whole cell (ex: sperm)

  • Microvilli → tiny finger-like folds, increase surface area for absorption (ex: intestines)

• Importance: help cells move, sense, or absorb nutrients

💡 Quick tip: Cilia = sweep, Flagella = swim, Microvilli = absorb

Cilia

• Definition: short, hair-like extensions on cell surface

• Function: move substances across the cell surface

• Shorter + more numerous than flagella

• All of __ have sensory functions

• Location / Example: lining the respiratory tract → sweep mucus & dust out of airways

• Importance: keep airways clear; help movement in some cells

💡 = tiny hairs that sweep

Microvilli

• Definition: tiny finger-like projections on cell surface

• Function: increase surface area for absorption

• Location / Example: found in small intestine → absorb nutrients from food

• Importance: make absorption faster and more efficient

💡 = “absorption fingers”

Flagella

• Definition: long, tail-like extension of a cell

• Function: moves the entire cell

• Only found on human sperm cells

• Location / Example: sperm cell → flagellum helps it swim to the egg

• Importance: allows mobility in certain cells

💡 = “tail for swimming”

Cell Process Movement

1. Signal → Cell gets a signal to move (chemicals, environment, etc.).

2. ATP provides energy → Needed for movement.

3. Cytoskeleton = engine

   • Microtubules → act like tracks that guide cilia & flagella.

   • Microfilaments → help the cell crawl or change shape.

4. Movement types:

   • Cilia → microtubules inside beat back & forth → move mucus/dust (like oars).

   • Flagella → microtubules whip tail-like → move the whole cell (like a fish tail).

   • Microvilli → supported by microfilaments → don’t move, but increase absorption (like a sponge).

Importance: lets cells move substances, travel (sperm), or absorb nutrients (intestines).

💡 Cytoskeleton = engine → powers cilia, flagella, microvilli.

• Cilia = oars paddling water, Flagella = fish tail swimming, Microvilli = sponge soaking up nutrients

Nucleus

• Definition: control center of the cell

• Function: stores DNA (genetic info) and controls cell activities (growth, metabolism, protein synthesis)

• Site of transcription

• Structures inside:

  • Nuclear envelope → protects nucleus, controls what enters/leaves

  • Nucleolus → makes ribosomes

  • Chromatin → DNA + proteins

• Importance: without it, the cell can’t function or reproduce

💡 = cell’s brain (controls & stores DNA)

Chromatin vs Chromosomes

Definition: loose, uncoiled form of DNA + proteins

• Function: allows easy access to DNA for transcription & replication

• When: found when the cell is not dividing

Chromosomes

• Definition: tightly coiled, condensed form of DNA

• Function: keeps DNA organized & safe during cell division

• When: visible only when the cell is dividing

• Both are located inside the nucleus

💡 Quick tip: Chromatin = relaxed (normal life), Chromosomes = condensed (cell division)

Nucleus enveleope

• Definition: double membrane that surrounds the nucleus

• Structure:

  • Inner membrane: supports nucleus structure

  • Outer membrane: continuous with rough ER, may have ribosomes

• Function:

  • Protects DNA

  • Controls what enters and leaves the nucleus via nuclear pores

• Location: around the nucleus

💡 = nucleus’ protective barrier + gatekeeper

Nucleous

• Definition: dense structure inside the nucleus

• Function / Importance:

  • Makes ribosomal RNA (rRNA)

  • Assembles ribosome subunits to send to the cytoplasm

• Location: inside the nucleus, floating in nucleoplasm

• Example / Situation: think of it as a ribosome factory inside the nucleus

💡= ribosome-making factory in the nucleus

Cell connections

• Definition: structures that link cells together in tissues

• Types & Functions:

  • Tight junctions: seal cells → prevent leaks (ex: lining of intestines)

  • Desmosomes: anchor cells → resist stretching (ex: skin)

  • Gap junctions: channels → allow communication & molecule exchange (ex: heart cells)

• Importance: maintain tissue integrity, communication, and protection

💡 = bridges & gates between cells

Densosomes

• Definition: strong cell-to-cell anchoring junctions

• Structure: protein fibers on outer surface interlock with fibers of neighboring cells

• Function / Importance:

  • Hold cells together

  • Resist stretching and mechanical stress

• Permeability: not fully sealed, some substances can pass

• Location / Example: skin, heart tissue

• Analogy: like spot welds or Velcro keeping cells tightly connected

💡 = “interlocking anchors” for strength + some permeability

Gap Junctions

• Definition: channels that electrically and physically connect neighboring cells

• Structure: gaps/tunnels that join the cytoplasm and fuse plasma membranes

• Function / Importance:

  • Allow ions, nutrients, small molecules, and signals to pass directly between cells

  • Enable rapid communication and coordination (ex: heartbeat)

• Location / Example: cardiac muscle and some smooth muscle

• Analogy / Quick tip: tiny tunnels or bridges that connect cells for communication
  = cell-to-cell tunnels for communication

Tight Junction

• Definition: seal neighboring cells together to prevent leaks

• Structure: proteins fuse plasma membranes at contact points

• Function / Importance:

  • Create a barrier that blocks movement of substances between cells

  • Maintain tissue integrity and control what enters/exits

• Location / Example: lining of intestines → prevent digestive fluids from leaking

• Analogy / Quick tip: Tight junctions = waterproof seal between cells

Cell Life Cycle

• Definition: series of stages a cell goes through from formation to division

• Main Phases:

  1. Interphase – cell grows, performs normal functions, and prepares for division

     • G1: growth

     • S: DNA replication

     • G2: preparation for mitosis

  2. Mitotic Phase (M phase) – cell divides

     • Mitosis: division of nucleus (prophase, metaphase, anaphase, telophase)

     • Cytokinesis: division of cytoplasm → 2 daughter cells

• Importance: ensures growth, repair, and replacement of cells

• Example / Situation: skin cells constantly divide to replace dead cells

💡 = grow, copy DNA, divide

Interphase

• Definition: the longest phase of the cell cycle where the cell grows and prepares for division

• Subphases:

  • G1: cell grows, performs normal functions

  • S: DNA replication (copies genetic material)

  • G2: prepares for mitosis, makes organelles & proteins needed for division

• Importance: ensures the cell is ready to divide accurately and efficiently

• Example / Situation: skin cells growing and copying DNA before dividing

💡 = cell’s prep & growth stage

M Phase

• Definition: phase of the cell cycle where the cell actually divides

• Subphases:

  • Mitosis: division of the nucleus

    • Prophase, Metaphase, Anaphase, Telophase

  • Cytokinesis: division of the cytoplasm, forming 2 daughter cells

  • Cell divides through creating new offsprings/daughters cells

• Importance: ensures each new cell gets a complete set of DNA and organelles

• Example / Situation: skin cells divide to replace dead cells

💡 Quick tip: M Phase = the “splitting” stage of the cell cycle

DNA Replication

• Definition: process of copying DNA before cell division

• Location: occurs in the nucleus during S phase of interphase

• Function / Importance:

  • Ensures each daughter cell gets an exact copy of DNA

  • Maintains genetic continuity

• Process (simplified):

  1. Helicase unwinds the DNA double helix

  2. DNA polymerase builds new complementary strands (A + T / C + G)

  3. Two new complete identical DNA molecules are formed

• Example / Situation: skin cells replicating DNA before mitosis

💡 = copying the cell’s instruction manual

Central Dogma

• Definition: the flow of genetic information in a cell

• Process:

  1. DNA → RNA (Transcription)

  2. RNA → Protein (Translation)

• Function / Importance:

  • DNA stores information

  • RNA carries the instructions

  • Proteins perform cell functions and structure

• Example / Situation: DNA in your cells codes for insulin protein through transcription and translation

💡 = DNA → RNA → Protein

Why is DNA Replication so important?

• If there’s a problem in DNA, then there will also be a problem in RNA —— leading to mutations in proteins

• Because proteins are used structurally and functionally in the body, which can cause body wide problems

When interphase completes cell divison can begin..

• Concept: Once interphase (growth + DNA replication) is complete, the cell has enough resources and copied DNA to begin cell division (M Phase).

• Importance: ensures accurate division so each daughter cell gets a complete set of DNA and organelles.

Cellular Respiration

• Definition: process by which cells break down glucose to produce energy (ATP)

• Location: occurs in cytoplasm (glycolysis) and mitochondria (Krebs cycle + electron transport chain)

• Purpose / Importance: provides energy for all cell activities

• Process (simplified):

  1. Glycolysis – glucose → pyruvate + 2 ATP (cytoplasm)

  2. Krebs Cycle – pyruvate → CO₂ + 2 ATP + electron carriers (mitochondria)

  3. Electron Transport Chain – electrons → 34 ATP + water (mitochondria)

• Examples / Situation: powers muscle contraction, nerve signals, and active transport

💡 = turning sugar into usable energy (ATP)

Mitosis

• Definition: division of the nucleus to produce two identical daughter cells (diploid)

• Location: occurs in the nucleus during M phase of the cell cycle

• Purpose / Importance: ensures each new cell gets a complete set of DNA

• Vast majority of cells undergo this type of replication

• Phases (simplified):

  1. Prophase – chromosomes condense, spindle forms

  2. Metaphase – chromosomes line up in the center

  3. Anaphase – sister chromatids are pulled apart

  4. Telophase – nuclear envelope reforms around separated DNA

• Example / Situation: skin cells dividing to replace dead cells

💡 = copying and splitting DNA for growth & repair

Meiosis

• Definition: type of cell division that produces gametes (sperm or egg) with half the DNA of the parent cell

• Results in four genetically unique haploid daughter cells

• Location: occurs in reproductive organs (ovaries and testes)

• Purpose / Importance: ensures genetic diversity and correct chromosome number in offspring

• Phases (simplified):

  1. Meiosis I – homologous chromosomes separate → 2 cells

  2. Meiosis II – sister chromatids separate → 4 haploid gametes

• Example / Situation: sperm and egg cells formation for sexual reproduction

💡 = making gametes with half the DNA

Prophase

• Definition: first stage of mitosis

• Key Events / Structures:

  • Chromosomes condense and become visible

  • Spindle fibers start forming from centrosomes

  • Nuclear envelope begins to break down

• Function / Importance: prepares chromosomes for alignment and separation

• Example / Situation: skin cell preparing to divide

💡 = chromosomes condense, spindle forms, nuclear envelope disappears

Metaphase

Definition: second stage of mitosis

• Key Events / Structures:

  • Chromosomes line up at the cell’s equator (metaphase plate)

  • Spindle fibers attach to chromosome centromeres

• Function / Importance: ensures each daughter cell will get an identical set of chromosomes

• Example / Situation: skin cell lining up chromosomes before being pulled apart

💡 = chromosomes line up in the middle

Anaphase

• Definition: third stage of mitosis

• Key Events / Structures:

• Centrosome of each chromosome splits to form two chromatids

  • Sister chromatids are pulled apart toward opposite poles of the cell

  • Spindle fibers shorten to move the chromatids

• Function / Importance: ensures each daughter cell receives an identical set of chromosomes

• Example / Situation: skin cell separating its DNA before division

💡 Quick tip: Anaphase = sister chromatids are pulled apart

Telophase

• Definition: last stage of mitosis before the cell splits

• Key Events:

  • Chromosomes loosen back into chromatin

  • Nuclear envelope forms around DNA

  • Spindle fibers disappear

• Function: gets the cell ready to divide into two daughter cells

• Example: skin cell finishing division

💡 = DNA relaxes, nuclei form, ready to split

Cytokinesis

• Definition: division of the cytoplasm after mitosis

• Key Events:

  • Cell membrane pinches in (animal cells) or cell plate forms (plant cells)

  • Two daughter cells are formed, each with its own nucleus and organelles

• Function / Importance: completes cell division so each cell can function independently

• Example / Situation: skin cell splitting into two new cells

💡 = cytoplasm divides, forming two new cells

True or false? During Mitosis one diploid parent cell divides to form two identical diploid daughter cells

True — During mitosis, one diploid parent cell divides to form two identical diploid daughter cells with the same number of chromosomes as the parent.

Similarites vs Differences between Mitosis and Meiosis

Similarities:

1. Both are types of cell division

2. Both replicate DNA before dividing

3. Both go through stages: prophase, metaphase, anaphase, telophase

Differences:

• Purpose:

  • Mitosis → growth, repair, asexual reproduction

  • Meiosis → produce gametes for sexual reproduction

• Number of divisions: Mitosis = 1, Meiosis = 2

• Number of daughter cells: Mitosis = 2, Meiosis = 4

• Chromosome number: Mitosis = diploid, Meiosis = haploid

• Genetic variation: Mitosis = identical, Meiosis = unique

• Location: Mitosis = body cells, Meiosis = reproductive organs

💡 Mitosis = 2 identical cells, Meiosis = 4 unique gametes