Cell Biology Notes

Cells

What are Cells?

• A cell is the smallest unit that can carry on all the processes of life.
• All organisms are made of cells.
• Organisms are made of several organ systems.
• Each organ system contains several organs.
• Each organ contains several tissues.
• Each tissue is made of cells.
• Cells contain small microstructures called organelles.

Animal vs Plant Cell

Typical Animal Cell

• Nucleus
• Mitochondria
• Cell membrane
• Cytoplasm
• Ribosomes

Typical Plant Cell

• Cell membrane
• Ribosomes
• Rough Endoplasmic Reticulum
• Cell wall (made from cellulose)
• Cytoplasm
• Permanent vacuole
• Chloroplast
• Nucleus
• Mitochondrion

Similarities: Features Found in Both Plant and Animal Cells

• Mitochondria:
  • An organelle that uses glucose and oxygen to make ATP (energy).
  • This process is called respiration.
• Cell surface membrane:
  • A partially permeable bilayer membrane separating the cell from the environment.
  • Made of lipid and protein.
  • Controls the movement of substances in and out of the cell.
  • Strong but flexible.
• Cytoplasm:
  • A jellylike substance made of mostly water and protein.
  • Metabolic reactions occur in it.
• Nucleus:
  • A spherical organelle that stores genetic material.
  • Contains DNA that codes for proteins.
  • Controls the activities of the cell such as cell division and protein synthesis.

Differences: Features found in only plant cells

• Cell Wall:
  • A rigid layer surrounding the cell made of cellulose.
  • Gives the plant its shape and prevents it from bursting.
  • Animals don’t have it.
• Chloroplasts:
  • Sacs which contain chlorophyll, a green pigment that traps sunlight for photosynthesis.
  • Animals don’t have it.
• Vacuole:
  • A large room in the center of the cell.
  • Stores sugars and salts and controls the movement of water in and out of the cell.
  • Animals have small vesicles, not a large vacuole.
• Plant cells store sugars as starch, while animal cells store sugars as glycogen.
• Animal cells have an irregular shape, but plant cells have a regular shape.

Types of Cells - Important to Know

Red Blood Cells

• Made in bone marrow.
• Carry O2 and CO2.
• No nucleus.
• Cell membrane
• Contain Haemoglobin
• Concave surface.

Muscle Cells

• Extremely rich in mitochondria.
• Produces heat.
• Contract and relax.

Ciliated Cells

• Hair-like appendages present.
• Acts like a brush, sweeps away dust and mucus (traps pathogens).
• Mucus is made by goblet cells.

Nerve Cells

• Detects and responds to stimuli.
• Carries electric energy/impulses.
• Cell membrane
• Cytoplasm
• Dendrite
• Nucleus
• Nerve ending
• Axon

Xylem Cells

• Dead cells containing lignin.
• Hard and rigid.
• Transport water and minerals.
• Thick cell wall containing lignin.
• Thin area of cell wall (pit).
• Space containing no cytoplasm.
• Gap where end wall of cell has been lost.

Sperm Cell

• Male reproductive cell.
• Nucleus and DNA in head
• Mitochondria in mid piece
• Acrosome in head.
• Fuses with egg cell to make a zygote.
• Has a tail to swim.