Unit 2 cells

Life functions/processes:

  • Metabolism → essential chemical reactions

  • Reproduction → reproduce, either asexually or sexually

  • Sensitivity → responses to external or internal stimuli

  • Homeostasis → maintenance of a stable internal environment

  • Excretion → removal of waste products

  • Nutrition → exchange of materials & gases w environment

  • Growth/movement → move and change shape or size

Unicellular

  • single cell organisms → only an organism if it can carry out the life processes

  • paramecium

    • unicellular organism

    • found in stagnant ponds

    • heterotrophs (feed on food particles found in environment)

    • move in all directions using cilia

  • Chlamydomonas

    • class of unicellular green algae

    • size from 10 to 30 µm in diameter

    • have a cell, wall, chloroplast, mitochondria, an ‘eye’ that detects light, 2 flagelas

Life Functions

Paramecium

Chlamydomonas

Metabolism

Breaking down nutrients from their env.→ rely on external sources for energy and carbon compounds

Flexible metabolism → can grow through heterotrophically (getting food from other organisms) or mixotrophically (making its own food or getting it from other)

Reproduction

Carries sexual and asexual reproduction → binary fission (asexual)

Carries sexual & asexual reproduction → binary fission & sexual repr.

Sensitivity

Detect changes in water temp. → go to warmer temperatures

Detect light changes using its eye spot → go to brighter region to increase photsynthesis

Homeostasis

Osmoregulation. A constant internal environment → collecting excess water in contractile vacuoles → expelling it through plasma membrane

Osmoregulation. A constant internal environment → collecting excess water in contractile vacuoles → expelling it through plasma membrane

Excretion

Metabolic waste collects in vacuoles → moves to anal pore → expelling waste into environment

Uses whole surface of plasma membrane →excrete waste products

Nutrition

Heterotroph → takes is food through vacuoles where digestion happens

Autotroph → uses large chloroplast for photosynthesis → produces food

Growth

After eating, it reaches a certain size and splits into 2 daughter cells

Producing organic molecules in photosynthesis→increases its size → split into 2 daughter cells

Movement

Cilia propels it due to changes in environment

Flagella rotates → moving towards better environment

Cell Theory

  • cell is the smallest unit of life

  • cells can only arise from pre-existing cells

  • all living things are composed of cells

Cell structures common to all cells

  • plasma membrane → outer border maintain chemical chemistry (Homeostasis)

  • cytoplasm → internal fluid that functions as a reaction medium for metabolic processes

  • DNA → coded instructions that function to control internal activities

atypical cell structure in eukaryotes

  • striated muscle fibers

    • Cells fuse to form long muscle fibers with multiple nuclei.

    • Surrounded by a continuous plasma membrane.

    • Challenges the idea that living things are made up of discrete cell units.

  • Aseptate Fungal Hyphae:

    • Filamentous structures (hyphae) used for growth and nutrient absorption.

    • Some hyphae have a continuous cytoplasm with multiple nuclei (no internal walls).

    • Challenges the idea that living structures are made of autonomous cells.

  • Sieve Element Cells (in plants):

    • Sieve elements form interconnected assemblies through plasmodesmata.

    • Lack nuclei and rely on companion cells for survival.

    • Challenges the idea that multicellular structures are made of independent cells.

  • Red Blood Cells:

    • Mature cells lack a nucleus and mitochondria.

    • Cannot replicate independently; new cells are produced in the bone marrow.

    • Challenges the definition of eukaryotic cells as they lack structures for autonomous survival.

Microscopes

  • Light microscopes

    • view living specimens in their natural colours

    • clarity can be improved via the use the of stains

  • Electron microscope

    • generate images at a much higher magnification & resolution

    • cannot view living specimens nor colors

      • Electron Beam 1: Transmission (TEMs)

        • cross section image

      • Electron Beam 2: Scanning (SEMs)

        • 3D image

Different Microscope techniques

  • Fluorescent stains and immunofluorescence →Absorb lights transmit a color -

  • Freeze fracture electron microscopy → freeze specimen then break to see what's inside the cell

  • Cryonic electron microscopy → taking detailed images of tiny biological structures by freezing them to preserve their natural state