Cell Biology

What’s in Cells ?

Cells

The BASIC unit of living organisms.

Provide STRUCTURE and carry out certain FUNCTIONS

Eukaryotic Cells

  • Plants, animals, fungi, protists

  • 10 - 100 μm (micrometers)

  • An eukaryote is an ORGANISM made of eukaryotic cells

Prokaryotic Cells

  • Bacteria

  • 0.1 - 5.0 μm

  • A prokaryote is an ORGANISM made of prokaryotic cells

Prokaryotic cell properties

  • Single DNA loop

  • Do not have a nucleus

    • so GENETIC MATERIAL stores in a single DNA loop in CYTOPLASM

  • NO mitochondria

  • NO chloroplasts

  • NO nucleus

  • Some contain PLASMIDS (small rings of DNA)

    • replicate and move between cells to SHARE GENETIC INFO

Eukaryotic sub-cellular

  • Cell membrane - separates interior of cell to the environment outside, SELECTIVELY PERMEABLE (controls substances moving in & out of cell)

  • Cytoplasm - Jelly-like fluid, outside nucleus, where CHEMICAL REACTIONS take place

  • Nucleus - Contains the GENETIC MATERIAL (as chromosomes)

Prokaryotic sub-cellular

  • Plasmids - small RINGS of DNA, can replicate & move between cells to share GENETIC INFORMATION

Animal Cells

Sub-cellular structures:

  • Cell membrane

  • Nucleus

  • Ribosomes - responsible for PROTEIN SYNTHESIS (making proteins)

  • Mitochondria - where AEROBIC respiration occurs (uses glucose & oxygen to release energy)

  • Cytoplasm

    • e.g. -

      • Skin cells

      • muscle cells

      • blood cells

      • nerve cells

      • fat cells

Plant Cells

Sub-cellular structures

  • Cell membrane

  • Nucleus

  • Ribosomes

  • Mitochondria

  • Cytoplasm

  • Permanent vacuole - fluid filled sac, stores water, enclosed in a membrane, (can make up to 90% of plant cell volume) keeps the cell TURGID

  • Chloroplasts - contain chlorophyll, required for photosynthesis

  • Cell wall - surrounds the cell, (made of cellulose), strengthens the STRUCTURE of cell

Resolution - the ability to distinguish between two objects that are close together when magnified

1 milimeter = 1 × 10-3m

1 micrometer = 1 × 10-6m

1 nanometer = 1 × 10-9m

Cell Differentiation - the process where cells gain new, different SUB-CELLULAR structures, to let it perform a specific function. Cell —> specialized

methylene blue as stain

Plant & Animal Differentiation

Plants

  • Many can differentiate throughout their lives

  • They are always able to create new tissues

Animal

  • Differentiate early on in development (e.g. in embryo)

  • In mature animals, cells divide to replace cells & repair tissues

  • New tissues are rarely created by cell differentiation

Bacterial Cells

Sub-cellular structures

  • Plasmids

  • Cell wall

  • Cell membrane

  • Cytoplasm

  • Flagella (the tail)

  • Pili (the hairs)

Animal Cell Differentiation (in depth)

  • In embryos:

    • differentiation happens during an organism’s development

    • organisms start as ONE cell

    • These cells divide to form embryos that differentiate (they become specialised) to produce cells that can perform the body’s functions

  • In plants:

    • (Many) plant cells keep their ability to differentiate throughout their life

    • So, plants are able to create new tissues

  • Adult animals:

    • Cell differentiation is rare

    • Their cells mostly divide to replace cells and to repair tissues

    • NEW tissues are RARELY created

Sperm Cell

Sub-cellular structures

  • Flagellum - used for movement, allows sperm to travel towards the egg cell

  • Middle section - filled with mitochondria, provides the sperm with energy

  • Acrosome - at the tip of the head, contains digestive enzymes to penetrate egg cell

  • Head - contains the nucleus (combines with the egg cell's half of genetic material, to fertilize egg cell)

Nerve Cell

Nerve cells are specialized to transmit ELECTRICAL MESSAGES/SIGNALS around the body

Sub-cellular structures

  • Axon - electrical signals travel along the axon

    • Nerve cells have a long axon, increases the distance that signals can travel

  • Myelin sheath - A sheath made of MYELIN, surrounds the axon, stops nerve signals from LEAKING OUT OF THE CELL, increases the speed of transmission of signals

  • Dendrites - Branches of a new cell, several dendrites spread outwards from the cell body to transfer electrical messages to other neurons, electrical messages travel at synapses

Muscle Cell

Specialized, can produce force and motion

  • Mitochondria - energy for motion

  • Protein fibres - cab contract, allowing the muscle to move

Root Hair Cell

Specialized to allow plant to absorb more water

  • No chloroplasts

  • Long projections, increase surface area that the plant can use to absorb water & minerals

Xylem Cells

Specialized to transport water up the stem of a plant, into the leaves

  • open ended cells - allows water to move through

  • lignin - strengthens xylem cell walls