all exam questions

• Exceptions to cell theory

  • Skeletal muscle fibers are larger/have many nuclei/are not typical cells
  • Fungal hyphae are (sometimes) not divided up into individual cells
  • Unicellular organisms can be considered acellular because they are larger than a typical cell/carry out all functions of life
  • Some tissues/organs contain large amounts of extracellular material e.g. vitreous humor of eye/ mineral deposits in bone/ xylem in trees
• Statement of cell theory: all living things/most tissues are composed entirely of true cells
• Extracellular component


  e.g. plant cell wall/cellulose/interstitial matrix/basement membrane/glycoprotein/bone matrix

  
• Functions of extracellular component


  • Strengthens/supports the cell/plant (against gravity)
  • Prevents the entry of pathogens
  • Maintains the shape of plant cells
  • Allows turgor pressure/high pressure to develop inside the cell
  • Prevents excessive entry of water to the cell
  • Helps cells to stick together/adhere
  • Needed to hold cells/tissues together
  • Forms interstitial matrix / forms basement membrane to support single layers of cells
  • Forms (part of the) filtration membrane in the glomerulus
• Surface area to volume ratio

  Small cells have larger ratio (than larger cells)/ratio decreases as size increases<|>Surface area/membrane must be large enough to absorb nutrients/oxygen/substances needed<|>Surface area/membrane must be large enough to excrete/pass out waste products<|>Need for materials is determined by (cell) volume<|>Cell size is limited (by SA/Volume ratio)/cells divide when they reach a certain size
• Reference to diffusion across/through membrane/surface area
• Differentiation


  Development in different/specific ways<|>Cells carry out specialized functions/become specialized<|>Cells have all genes/could develop in any way<|>Some genes are switched on/expressed but not others<|>Position/hormones/cell-to-cell signals/chemicals determine how a cell develops<|>A group of differentiated cells is a tissue
• Stem cells


  Undifferentiated cells<|>Embryo cells are stem cells<|>Stem cells can differentiate in many/all ways / are pluripotent/totipotent<|>Differentiation involves expressing some genes but not others<|>Stem cells can be used to repair/replace tissues/heal wounds
• Ultrastructure of Escherichia coli

  1. Cell wall

  2. Plasma membrane

  3. Cytoplasm

  4. Pilus/pili

  5. Flagellum/flagella

  6. 70S ribosomes

  7. Nucleoid / naked DNA

  
• Approximate width 0.5 μm / approximate length 2.0 μm
• Organelles in plant cell cytoplasm

  1. Rough endoplasmic reticulum

  2. Free ribosomes

  3. Golgi apparatus

  4. Mitochondrion

  5. Chloroplast

  6. Vacuole

  7. Nucleus

  8. Lysosome

  9. Smooth endoplasmic reticulum
• Ultrastructure of liver cell

  1. (Plasma) membrane

  2. Nucleus

  3. Mitochondria(ion)

  4. Rough endoplasmic reticulum

  5. Golgi apparatus

  6. Ribosomes

  7. Lysosome

  
• Functions of organelles


  Lysosome: hydrolysis/digestion/break down of materials (macromolecules)<|>Golgi apparatus: synthesis/sorting/transporting/secretion of cell products<|>Rough endoplasmic reticulum: site of synthesis of proteins (to be secreted)/ intracellular transport of polypeptides to Golgi apparatus<|>Nucleus: controls cells activities/mitosis/replication of DNA/transcription of DNA (to RNA)/directs protein synthesis<|>Mitochondrion: (aerobic) respiration/generates ATP
• Differences between plant and animal cells

  • Plant cells have cell walls, animals do not
  • Plant cells have plastids/ chloroplasts, animals do not
  • Plant cells have a large central vacuole, animals do not
  • Plant cells store starch, animal cells store glycogen
  • Plant cells have plasmodesmata, animal cells do not
  • Plant cells have fixed shape / more regular shape
  • Animal cells have centrioles, plant cells do not
  • Animal cells have cholesterol in the cell membrane, plant cells do not
  • Animal cells are more rounded
• Differences between prokaryotic and eukaryotic cells

  • Prokaryotic: Naked/loop of DNA, Eukaryotic: DNA associated with protein/histones/nucleosomes/DNA in chromosomes
  • Prokaryotic: DNA located in cytoplasm/nucleoid/no nucleus, Eukaryotic: DNA located within a nucleus/nuclear membrane
  • Prokaryotic: Membrane bound organelles absent, Eukaryotic: Membrane bound organelles present
  • Prokaryotic: 70S Ribosomes, Eukaryotic: 80S Ribosomes
  • Prokaryotic: Same plasma membrane structure as Eukaryotic cells, Eukaryotic: Same plasma membrane structure as Prokaryotic cells
  • Prokaryotic: Cell wall is composed of peptidoglycan/not composed of cellulose/not composed of chitin, Eukaryotic: Cell wall is composed of cellulose/chitin/not composed of peptidoglycan
  • Prokaryotic: Mitochondria absent, Eukaryotic: Mitochondria present
  • Prokaryotic: Pili present, Eukaryotic: Pili absent
  • Prokaryotic: Plasmids (sometimes) present, Eukaryotic: Plasmids absent
  • Prokaryotic: Flagella solid, Eukaryotic: Flagella flexible/membrane-bound
• Structure of cell membrane

  1. Phospholipids with hydrophilic heads and hydrophobic tails

  2. Phospholipid bilayer

  3. Proteins in the bilayer

  4. Transmembrane and peripheral/extrinsic proteins

  5. Glycoproteins

  6. Cholesterol

  7. Glycolipids

  8. Thickness shown as 10 nm/ + or - 2 nm

  
• Phospholipid structure


  Hydrophobic tail/hydrophilic head<|>Head made from glycerol and phosphate<|>Tail made from two fatty acids<|>Saturated/ unsaturated fatty acid (in tail)
• Arrangement of phospholipids in membrane

  Phospholipids form a bilayer<|>Heads face outside the membrane/ tails face inside the membrane/ hydrophic interior/ hydrophilic exterior of membrane<|>Phospholipids held together by hydrophobic interactions<|>Phospholipid layers are stabilized by interaction of hydrophilic heads and surrounding water

  
• Properties of phospholipids


  • Phospholipids allow for membrane fluidity/ flexibility
  • Fluidity/ flexibility helps membranes to be (functionally) stable
  • Phospholipids with short fatty acids/ unsaturated fatty acids are more fluid
  • Fluidity is important in breaking and remaking membranes (e.g. endocytosis/ exocytosis)
  • Phospholipids can move about/ move horizontally/ "flip flop" to increase fluidity
• Cell Division


  1. DNA replication

  2. DNA transcription

  3. Enzyme/protein synthesis

  4. Biochemical reactions/example of a biochemical reaction

  5. Cell respiration

  6. Growth

  7. Organelles replicated
• Relationship between amino acids and dipeptides

  1. Condensation/dehydration synthesis: water produced (when two amino acids joined)

  2. Hydrolysis: water needed to break bond

  3. Dipeptide --> amino acids - hydrolysis occurs

  4. Amino acids --> dipeptide - condensation occurs
• α-D-glucose


  Molecule of α-D-glucose
• β-D-glucose


  Molecule of β-D-glucose
• Amino acid


  Molecule of amino acid
• Fatty acid


  Molecule of fatty acid
• Ribose


  Molecule of ribose
• Water


  • High specific heat capacity
  • Large amount of heat causes small increase in temperature
  • High latent heat of vaporization
  • Large amount of heat energy needed to vaporize/evaporate
  • Hydrogen bonds between water molecules make them cohesive/stick together
• Water


  Polar molecules, good solvent
• Surface tension of water


  Allows some organisms (e.g. insects) to move on water's surface
• Polarity/capillarity/adhesion of water


  Helps plants transport water
• Water as solvent


  Capable of dissolving substances for transport in organisms
• Water's thermal properties (high heat of vaporization)

  Excellent coolant
• Ice floats


  Lakes/oceans do not freeze, allowing life under the ice
• Water's buoyancy


  Supports organisms
• Water's structure


  Turgor in plant cells/hydrostatic pressure
• Water as habitat


  Place for aquatic organisms to live
• Carbohydrates for energy storage

  Stored as glycogen (in liver)<|>Short-term energy storage<|>More easily digested than lipids so energy can be released more quickly<|>More soluble in water for easier transport
• Lipids for energy storage

  Stored as fat in animals<|>Long-term energy storage<|>More energy per gram than carbohydrates<|>Lipids are insoluble in water so less osmotic effect
• Functions of lipids


  • Energy storage/source of energy/respiration substrate
  • (Heat) insulation
  • Protection (of internal organs)
  • Water proofing/cuticle
  • Buoyancy
  • (Structural) component of cell membranes
  • Electrical insulation by myelin sheath
  • (Steroid) hormones
  • Glycolipids acting as receptors
• Functions of proteins


  • Storage - zeatin (in corn seeds)/casein (in milk)
  • Transport - hemoglobin/lipoproteins (in blood)
  • Hormones - insulin/growth hormone/TSH/FSH/LH
  • Receptors - hormone receptor/neurotransmitter receptor/receptor in chemoreceptor cell
  • Movement - actin/myosin
  • Defense - antibodies/immunoglobin
  • Enzymes - catalase/RuBP carboxylase
  • Structure - collagen/keratin/tubulin/fibroin
  • Electron carriers - cytochromes
  • Pigments - rhodopsin
  • Active transport - sodium potassium pumps/calcium pumps
  • Facilitated diffusion - sodium channels/aquaporins