Biology- Unit 1 AOS 1

Chapter 2-3 of Units 1 Biology covers cells (Eukaryotic and Prokaryotic), Organelles, Cell shape and Size, The Plasma Membrane, Passive and Active transport, and tonicity on cells.

The cell theory states that?

• all organisms are made up of one or more cells

• all cells come from pre-existing cells

• cells are the smallest and most basic unit of life

Eukaryotic and Prokaryotic cells

• Eukaryotic

  • contains membrane bound organelles

  • contains nucleus

  • multi or unicellular

  • linear DNA

• Prokaryotic

  • no membrane organelles (including nucleus)

  • always unicellular

  • circular DNA

Organelles?

• structure of a cell with a specific function

Rough Endoplasmic Reticulum (RER)

• Produce and Modifies proteins

• Studded with ribosomes

Nucleus

• Double membrane that protects and confines DNA

• Controls cell growth, reproduction, and production of ribosomes.

Ribosomes

• Made up of ribosomal RNA

• Forms and synthesises proteins

Golgi apparatus

• modifies and packages proteins for export by cell

Lysome

• Breaks down cell waste and toxins

cell membrane

• Semipermeable barrier between a cells intercellular and extracellular environment

Mitochondria

• Site of aerobic cellular respiration

• Generates energy for cell

Mitochondria internal structure

Outer membrane, highly folded inner membrane to create a low volume space for cellular respiration.

• folds within the mitochondria increasing surface area - more efficient energy production

Cytoskeleton

• Network of proteins filaments

• help cells maintain shape, and movement.

Smooth Endoplasmic Reticulum (SER)

• produces lipids

Cell wall (plant cell)

• provides structure and protection to plant cell

Chloroplast (plant cell)

• Site of photosynthesis

  • Generating energy for plant cells through converting light energy to chemical energy (sugar)

Cellular respiration

• Is the breaking down of sugars to create energy

  • Aerobic cellular respiration - with oxygen

  • Anaerobic cellular respiration - without oxygen

Equation for aerobic cellular respiration

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (as ATP)

Glucose + Oxygen = Carbon Dioxide + Water + ATP

Equation for photosynthesis

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Light energy + Carbon Dioxide + Water = Glucose + Oxygen

Why are cells so small?

• Giving them a larger SA: V ratio

• Benefits:

  • Efficient and effective exchange of materials from extracellular environment (etc. import of water/ oxygen)

  • Intracellular transport of molecules are faster (smaller travel distance)

What increases the cells SA:V ratio

• Out-foldings for better absorption.

• If the cells main function is absorption

The plasma membrane is?

• phospholipid bilayer

  • embedded with proteins, carbohydrates and cholesterol

Phospholipid molecule components

• Phosphate head

  • Polar

  • hydrophilic (water loving)

• Fatty acid tails

  • non-polar

  • hydrophobic (dislikes water)

The cell membrane is also know as?

• The fluid mosaic structure

  • As components within the membrane (etc. phospholipids, proteins, carbohydrates, cholesterol) can move and shift giving it fluidity.

Role of proteins in cell membrane

• Makes the cell semi permeable

• channels and pumps certain substances through the membrane

Types of proteins within membrane

• Integral

  • apart of the membrane

• Transmembrane

  • spans the entire membrane

• Peripheral

  • attach onto membrane

Role of cholesterol in cell membrane

• Regulates fluidity and flexibility of membrane

Role of carbohydrates in cell membrane

• Aids in cell to cell communication

Passive and active transport and energy

• Passive

  • requires no energy

  • includes: simple diffusion, facilitated diffusion, osmosis.

• Active

  • Requires energy

Simple diffusion

• Type of passive transport

• small and hydrophobic molecules diffusing across the cell membrane by moving down concentration gradient.

  • High concentration - to low concentration.

Facilitated diffusion

• Type of passive transport

• Hydrophilic molecules moving through a cell membrane with the aid of a membrane protein.

Protein channels and Carrier proteins (facilitated diffusion)

• Protein channel

  • transmembrane protein pore within membrane, enabling transport of large and polar molecules.

• Carrier proteins

  • Bind to specific hydrophilic substances and undergo conformational change to transport molecule across membrane.

Osmosis

• Type of passive transport

• Transport of a solvent (typically water) through the cells membrane from a region of low solute (high water) to a region of high solute (low water)

Hypertonic and effect on cell

• When there is higher solute concentration (outside cell) than the cells cytoplasm, causing water to leave the cell.

  • cell will shrivel, caused plasmolyse

Hypotonic and effect on cell

• When there is low solute concentration (outside of a cell) than the cells cytoplasm, causing water to enter cell.

  • cell will bloat and grow, plant cell called turgid, animal cell called lysed

Isotonic and effect on cell

• When there is an equal solute concentration (outside the cell) to the cells cytoplasm.

  • cell will stay the same, animal cell normal, plant cell called flaccid.

Active transport

• Movement of dissolved substance against the concentration gradient (low to high concentration) with energy,

• for substance to come across the membrane with a carrier protein.

Process of active tranpsort

• target molecules binds to a ‘specific’ protein pump.

• conformational change then occurs when energy is released from the reaction of ATP to ADP plus 1 phosphate.

• Molecule then pushed through protein pump and released on other side of membrane.

Types of Bulk transport and molecules involved

• Exocytosis and Endocytosis = types of bulk transport

• Involves groups of molecules and large molecules

Endocytosis

• Part of plasma membrane encloses specific materials.

• Membrane then “pinches” off, forming a vesicle, moving into cytosol of cell.

Exocytosis

• Vesicles within cell fuses with the plasma membrane

• Vesicle then releases its contents out of the cell.

Differences between passive and active transport

• Active requires energy, whereas passive does not.

• Active transport molecules go against their concentration gradient, whereas in passive molecules go with their concentration gradient.

Molecules involved in active, passive and facilitated transport

• Active transport

  • sodium and potassium ions.

• Passive transport (diffusion)

  • oxygen, Carbon Dioxide molecules

• Facilitated diffusion

  • Ions, glucose, amino acid molecules