IB Bio 10

• Cell Theory:

  1. All living organisms are composed of one or more cells
  2. Cells are the smallest units of life
  3. All cells come from pre-existing cells
• Prokaryotes

  • Arose first
  • All unicellular
  • Do not have membrane-bound nucleus (no compartmentalization)
• Eukaryotes

  • Have a nucleus
  • Evolved after prokaryotes
  • Some are unicellular and some are multicellular
  • Contain membrane-bound organelles (are compartmentalized)
• Plasma Membrane/Cell Membrane

  • Controls the movement of substances
  • Composed of phosphlipids
  • Partially permeable (allows things to pass through it)
• Cytoplasm

  • Fluid filled space containing dissolved substances, enzymes, and organelles
• Cytoskeleton

  • Gives structure
  • Network of fibers (microfilaments) extending throughout the cytoplasm
• Nucleus (control center)

  • Brain of the cell
  • Contains genetic information in the form of chromosomes <- made of DNA
• Mitochondria

  • In plants and animals
  • Has a double membrane
  • Uses glucose to make chemical energy (ATP) t power the cell's biochemical reactions
• Ribosomes

  • Produce protein
  • Appears as dark granules in the cytoplasm
  • Site of protein synthesis (e.g. enzymes)
• Rough Endoplasmic Reticulum (rER)

  • Consists of flattened membrane sacs
  • Located near the nucleus
  • Ribosomes attached to rER <- why it's rough
  • Synthesizes proteins
  • rER in muscles are involved in muscle contraction
• Smooth Endoplasmic Reticulum

  • No ribosomes present
  • Involved with synthesis of steroids and lipids
• Golgi Apparatus (Golgi Body)

  • Consists of flattened membrane sacs
  • Processes (modifies) + distributes proteins from rER, lipids from smooth ER and other substances (shipping center)
  • Repackages proteins in vesicles for secretion outside the cell
  • Secretes mucus
• Plant Cells have the same organelles as animal cells except for;

  • Flagella <- Movement
  • Cilia <- Movement
  • Centrioles <- Mitosis
  • Lysosomes<- Chemicals that break down
• Vacuoles

  • Single membrane with fluid inside
  • Stores ions and nutrients
  • Contains enzymes that break down macromolecules and cell wastes
  • In plant cells, vacuoles are large and permanent (Central vacuole)
  • In animal cells, vacuoles are small and temporary
• Cell Wall (Only in plant cells)

  • Around the cell membrane
  • Walls consist mainly of cellulose
• Cellulose

  • Permeable - does not affect transport in and out of cell
  • Strong - gives support to the cell and prevents the plasma membrane bursting
  • Hard to digest - Resistant to being broken down
  • Lasts a long time without need for replacement
• Chloroplasts

  • Found only in plant cells
  • Involved in photosynthesis
  • Contains chlorophyll (pigment that makes stuff green)
  • Absorbs light energy and uses it to produce glucose <- photosynthesis
• Animal Cells

  • No cell wall (only plasma membrane)
  • No chloroplasts
  • Vacuoles not present or small
  • Contains centrioles in a centrosome area
  • Cell is flexible with round shape
  • Does not have plastids
• Plant Cells

  • Cell wall and plasma membrane present
  • Chloroplasts present
  • Large central vacuole
  • Does not contain centrioles with a centrosome area
  • Cell is rigid with fixed (angular) shape
  • Has plastids
• Animal Cell Diagram

  
• Plant Cell Diagram

  
• Why cells divide

  1. Transport
  2. Overheating
  3. Growth
  4. Asexual Reproduction
  5. Tissue Repair
  6. Embryonic Development
• Transport - Cell Division

  • If a cell is too big than substances will not be able to move as quickly around the cell where needed
  • Waste products in big cells will accumulate since they are produced faster than removed
• Overheating - Cell Division

  • Larger cells require more energy
  • Production of energy in big cells releases heat which can lead to overheating
• Growth - Cell Division

  • Multicellular organisms increase their size by increasing their number of cells through mitosis
  • Otherwise the Surface Area: Volume (SA:VOL) ration would be too low
• Asexual Reproduction - Cell Division

  • Certain eukaryotic organisms may reproduce asexually by mitosis (e.g. vegetative reproduction)
• Tissue Repair - Cell Division

  • Damaged, infected, or dead cells need to be repaired
• Embryonic Development - Cell Division

  • A fertilized egg (zygote) will undergo mitosis and differentiation in order to develop into an embryo
• Cell Cycle: Describes the major phases of activity in the division of a cell
• Cell Cycle

  • In order for cells to divide, each chromosome needs to make a copy of itself (replicate) so that the new cell has the same genetic information
  • The identical copies are called sister chromatids who are held together by chromosomes
  • When the cell divides, the sister chromatids separate into two different cells
• Sister Chromatids: Duplicated chromosomes attached by a centromere (after anaphase (when separated) they should be referred to as chromosomes)
• Centromere: Part of a chromosome that links sister chromatids
• Centrioles: Organize spindle microtubules during cell division
• In animal cells two centrioles are held by a protein mass referred to as spindle fibers
• Chromatin: Uncoiled form of DNA
• Cell Cycle Phases:

  1. Interphase
  2. Mitosis
  3. Cytokinesis
• Interphase

  • Cells spend 80% of its time in this phase of the cell cycle
  • Very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm
• • G0: Resting phase where the cell has left the cycle and stopped dividing <- still carry out their normal functions
  • G1: Rapid growth and metabolic activity (protein synthesis, mitochondria replication, chloroplast replication)
  • S: DNA synthesis and replication
  • G2: Centrioles replicate (preparing for cell division), DNA is condensed and coiled into chromosomes
• Mitosis

  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase (two)
• Prophase

  • Chromatin condenses (coils more tightly) to form chromosomes
  • Nuclear membrane broken down/disappears
  • Centrosomes move toward opposite poles of the cell due to lengthening microtubules
  • Mitotic spindle start to form between two centrioles (centrosomes)