Cell Structure

Table of Contents

Organelles

  • Little organs that carry out specialized functions.
  • Cellular machinery.

Prokaryotic organelles

prokaryotic-organelles.png

  • Also called no membrane-bound organelles.
  • These are organelles that are not inside of a membrane of a cell.

Plasma/Cell Membrane

  • It seperates what's inside and outside of the cell.
  • They let some things through such as food and energy, but also defends itself from the environment and other cells.
  • It is made of phospholipid bilayer and the different types of proteins floating around it.
  • The cell membrane is semi-permeable.

Phospholipids

  • class of lipids that are major component of all cell membranes.

Cell Wall

  • Outer layer of Plasma/Cell Membrane.
  • Made up of peptidoglycan, a polymer of sugars and amino acids that creates a mesh-like layer around the cell.
  • Its function is to provide additional protection for the cell.

Plants

  • It is in the cellulous.

Fungi

  • contain chitin.

Capsule

  • The outermost layer of the cell that provides the cover for the cell wall.

Cytoplasm

  • The interior of the cell is called the Cytoplasm.
  • Specifically, the fluid within the membrane is called cytosol.
  • Its a jelly-like fluid where all inside components are floating around.

Components

  • Cytosol
  • Interconnected filaments & fibers.
  • storage substances.

Nucleoid

  • Similar to the nucleus in a eukaryotic cell, this holds genetic information about the cell.
  • The Ribosome is responsible for the DNA transcription to happen.

Plasmid

  • A small, extrachromosomal DNA that is physicall seperated from the cell's DNA.
  • It can replicate independently and is also vital for the survival of a cell or organism.

Ribosomes

  • Sites of protein synthesis.
  • They are responsible for protein production as a product of DNA transcription.
  • It does this by binding itself to mRNA (messenger RNA) to determine the correct sequence of amino acids.
  • The DNA translation provides the protein (that includes enzymes from the DNA) and DNA polymerase.
  • The process also provides hexokinase which has a role in metabolism that provides the energy needed for the cell to function.
    • You can compare this to mitochondria in the eukaryotic cells.

Flagellum

flagella.png

  • Plural-form Flagella.
  • Whip-like extensions that allows a cell to move.
  • Found on sperm cells.
  • A hairlike appendage that has a couple of functions for motility.
  • The bacteria uses their flagella to:
    • move in fluid (motility),
    • in response to changes in concentration of chemical (chemotaxis)
    • movement in response to light (phototaxis) or movement in response to oxygen levels (aerotaxis)
    • helps in colonizing and infecting host organisms.

Types

  1. Bacterial flagella
  2. Archaeal flagella

Cilia

  • Latin word for "eyelashes".
  • tiny hairs on the surface of certain cells.
  • move in a rhythmic, sweeping motion and serve to move particles or cells in your body.
  • cilia lining in respiratory tract.
  • Tracheal cells
  • Beat and drive air impurities or foreign particles and mucus up the trachea to the mouth
  • Short
  • Used to move substances outside human cells.

Eukaryotic organelles

Interior Structures

Endoplasmic Reticulum

  • also called ER.
  • network of interconnected membranes.
  • it helps move substances within cells.
  • Types
    • Rough Endoplasmic Reticulum

      rough_er.png

      • Ribosomes attached to surface
      • Manufacture proteins
      • Ribosomes not permanently attached to Rough ER
      • May modify proteins from ribosomes
    • Smooth Endoplasmic Reticulum

      smooth_er.png

      • No attached ribosomes
      • Has enzymes that help build molecules
      • Contains Lipids

Golgi Apparatus

golgi_apparatus.png

  • Sorts proteins made by the ribosomes and sends them to needed places in the cell.
  • "the cell's post office"
  • Packaging & shipping station of cell.

Lysosomes

  • organelles that are filled with digestive enzymes to remove waste and invading bacteria.
  • Cell's suicide bags.
  • Functions
    • Aid in cell renewal.
    • Break down old cell parts.
    • Digests invaders.

Vacuoles

  • fluid filled organelles enclosed by a membrane.
  • Membrane bound storage sacs
  • Store materials such as food, sugar, water, and waste products
  • More common in plants than animals.

Mitochondria

  • "powerhouse" of the cell.
  • release energy for the cell.
  • converts the energy stored in glucose into ATP for the cell.
  • bound by double membrane.

Chloroplasts

  • Primary organelles for

Photosynthesis - chlorophyll

  • captures light energy and converts it into chemical energy through the process of photosynthesis.
  • Solar energy capturing organelle
  • absorbs all other colors except green.
  • Photosynthesis
    • Used by plants and other organisms to convert light energy into chemical energy
    • Energy Transformation
    • Takes place in the chloroplast.
    • Makes cellular food called glucose.
    • Equation

      \(6CO_{2} + 6H_{2}O \xrightarrow{\text{Light}} C_{6}H_{12}O_{6} + 6O_{2}\)

Cytoskeleton

cytoskeleton.png

  • network of protein filaments, fibers and tubules.
  • Functions
    • mechanical support
    • anchor organelles
    • it helps in moving substances
  • Composition
    • Microfilaments
      • thinnest
      • composed of the protein actin.
    • Microtubules
      • composed of protein tubulin
      • It is involved in nucleic and cell division, organization of intracellular structure, and intracellular transport, as well as ciliary and flagellar motility
    • Intermediate filaments
      • maintain cell shape and help bind some cells together.

Comparison of Structure

  Bacterium Animal Plant
Exterior Structures      
Cell Wall ✓ ✗ ✓
Plasma Membrane ✓ ✓ ✓
Flagella (cilla) – ✗ [1]
Interior Structure      
Endoplasmic Reticulum ✗ ↑ ↑
Microtubules ✗ ✓ ✓
Centrioles ✗ ✓ ✗
Golgi Apparatus ✗ ✓ ✓
Nucleus ✗ ✓ ✓
Mitochondria ✗ ✓ ✓
Chloroplasts ✗ ✗ ✓
Chromosomes [2] [3] [3]
Ribosomes ✓ ✓ ✓
Lysosomes ✗ ✓ ✓
Vacuoles ✗ ✗ or – [4]
  • [1] Sperm of a few species possess flagella.
  • [2] A single circle of naked DNA.
  • [3] Multiple units, DNA associated with protein.
  • [4] Usually a large single vacuole in a mature cell.

References

Cells

(Cell Theory > Cells > Cell Structure)

  • Parenchyma
    • (Types of Cells > Parenchyma > Chlorenchyma)
  • Chloroplasts
    • (Eukaryotic organelles > Interior Structures > Chloroplasts)

Eukaryotic Cells

Prokaryotic cells

Prokaryotes

  • (Differences > Prokaryotes)

Eukaryotes

  • (Differences > Eukaryotes)

Date: August 03, 2023

Author: Paul Gerald D. Pare

Emacs 29.1 (Org mode 9.6.6)