Important Information from Unit 1 and 2 of VCE biology

The cell theory

All organisms are composed of one or more cells, cells are the basic unit of structure and organisation in organisms, and all cells come from pre-existing cells.

Prokaryotic cells

Large SA:V ratio (beneficial for diffusion), single cell (unicellular), no membrane bound organelles or defined nucleus, cell wall, and DNA is a single and circular chromosome. Some have flagella or pili for movement. Small 1-10um.

organelles - cytoplasm, ribosomes, plasma membrane, genetic material.

eg. Bacteria and archaea.

Prokaryotes - Archaea (the extremophiles)

Unicellular

Found in volcanic vents, the Dead Sea, alkaline soils, and ocean floor

Anaerobic (don’t tolerate oxygen well)

Prokaryotes - Bacteria

Unicellular

Most are aerobes, some can be anaerobic.

Eukaryotic cells

Membrane bound organelles that have specialised functions, membrane bound nucleus, and DNA is inside the nucleus.

Multicellular, ability to form organ systems. large 10-1000um.

True nucleus DNA with multiple chromosomes condensed with histones (proteins that DNA wrap around).

eg. plants, fungi, animals, protists.

Eukaryotes - animal cell

Have 1 organelle that plant cells don’t, which is the centrioles.

Eukaryotes - plant cell

have 3 organelles that animal cells don’t have, which are chloroplasts, permanent large vacuole, and cell wall.

Compartmentalisation

Eukaryotes have membrane bound compartments (called organelles) inside the cell which perform specialised functions.

Allows processes that require different environments to happen at the same time. Makes the cell less vulnerable to changes in the external environment.

Plasma membrane (cell membrane)

Separates the interior of the cell from the outside environment.

found in prokaryotes and eukaryotes.

allows nutrients to enter the cell and waste the exit selectively.

has receptors that can communicate between other cells.

Nucleus

In eukaryotes, DNA and genetic information is contained in this.

Nuclear envelope

Surrounds the nuclear membrane

Nuclear pores

Allows nucleic acids in and out of the nucleus.

Nucleolus

Dense protein filled structure that creates ribosomal RNA and ribosomal subunits.

Ribosomes

The site of protein synthesis

One cell contains thousands of sub units (2 units joined together)

Found free in the cytoplasm or bound to rough endoplasmic reticulum

Found in eukaryotes and prokaryotes

Not membrane bound

Endoplasmic reticulum

Interconnecting system of thin membranes dividing the cytoplasm into compartments and channels - intercellular transporting system.

Rough endoplasmic reticulum (ER)

Has ribosomes attached, which makes proteins

Once proteins are made, they pass through the ER containing enzymes

Enzymes add sugar molecules to the proteins

Move into Golgi apparatus to be exported from the cell.

Smooth endoplasmic reticulum (ER)

Contains enzymes involved in the synthesis of molecules other than proteins (eg. phospholipids)

No ribosomes attached

Transport proteins, synthesis lipids and assist in producing the plasma membrane.

Golgi apparatus

Membrane bound

System of flattened membranes

Receive vesicles from the rough ER

Protein modification and final packaging of proteins before they are exported out of the cell (cell post office).

Mitochondria

Site of cellular respiration (energy producer - powerhouse of the cell)

Double membrane

Smooth outer membrane and highly folded inner membrane (creates a higher SA:V ratio)

Has its own circular DNA - passed down from the mother

Amount of this is relevant to the energy expenditure of the cell (eg. sperm cells have high numbers of this).

Lysosomes

The cell recycler

Membrane bound

Used in various cell processes such as the break down of unwanted matter

Contain digestive enzymes

Expels contents outside the cell (exocytosis)

Made by the Golgi apparatus

Only in animal cells.

Cytoplasm

Not organelles

All the content within the cell (organelles and cytosol)

Where chemical reactions are carried out

Cytosol

Not organelles

Fluid compartment of the cell that contains nutrients.

Cilia

Hair like structures on the surface of cells.

Flagella

Bacteria and sperm use this to swim/move.

Organelles

involved in specific functions, so their presence depends on the needs of the cell.

Cell wall

Provides structure and protection

In plants: cellulose (complex carbohydrate)

Plant, bacteria (peptidoglycan), fungi (chitin), and most algae have an additional one of this

Xylem

As cells age they die and loose their contents and create tube like cells- carry water from the roots to the leaves.

Chloroplast

Responsible for photosynthesis - converts light energy to chemical energy

Can move around the cell for optimal light absorption

Contains green pigment - chlorophyll

Thylakoid membranes are stacked many times to increase surface area.

Vacuole

Takes up majority of the cytoplasm in mature plant cells

Filled with fluid which serves as storage for sugars, minerals, water and proteins.