Advanced Bio Topic 1

Cell Theory

• All living organisms are made up of basic units called cells

• organisms are either unicellular or multicellular

• new cells are formed by the division of pre-existing cells

unicellular

made of one cell

multicellular

made of many cells

Cell

the basic unit of life

Common features

• plasma membrane

• cytoplasm

• DNA

• Ribosomes

plasma membrane

the boundary of the cell, it regulates which substances enter and leave the cell

cytoplasm

made of fluid or cytosol, containing dissolved substances and tiny structures called organelles

properties of a cell

3 dimensional

vary in shape and size

microscopic

cytosol

the liquid component of the cytoplasm, excluding organelles and where biochemical reactions occur.

DNA

carries hereditary information and codes for the production of the cell’s proteins; found in a nucleus (except bacteria)

organelle

a structure within a cell with a specialized function

membrane-bound organelle

a cell enclosed by a lipid membrane. eukaryotic cells have membrane-bound organelles

eukaryotes

have membrane bound organelles and organisms can be either unicellular (protistans) or multicellular (fungi, animals, plants)

prokaryotes

a single-celled organism that does not have a nucleus or membrane-bound organelles (bacteria, archaea)

Categories of all living things

Bacteria, Archaea, Protista, Plantae, Fungi, Animalia

ribosomes properties

• Not membrane-bound

• Found in both prokaryotes and eukaryotes

• Free in cytoplasm or attached to RER

• Very small (seen with electron microscope)

• Made of rRNA

ribosomes

site of protein synthesis (made of RNA)

nucleus properties

Enclosed within a porous nuclear membrane, contains nucleolus, and are found in almost all eukaryotic cells

nucleolus

inner dark region of the nucleus where ribosomes are assembled

nucleus

stores dna, and controls the activity of the cell

Mitochondria properties

Made of rod shaped organelles which occurs in metabolically active cells.

Inner membrane folded to form cristae, surrounded by fluid called matrix

Mitochondria

The site of aerobic cellular respiration where energy is released for cell function in the form of ATP (from glucose).

Rough Endoplasmic reticulum properties

a system of membranes with ribosomes, connected to the nucleus and extending into the cytoplasm.

vesicles

sacs that are used to transport proteins between organelles or to the cell membrane

Rough ER

modifies and transports proteins across the cell

Smooth Endoplasmic Reticulum properties

A system of membranes like the RER but without ribosomes, that pinches off into vesicles to carry lipids around the cell.

Smooth ER

synthesises and transports lipids (fats)

Golgi Apparatus

sacs that modifies and package proteins and lipids from the ER into vesicles for secretion to other organelles or outside of the cell.

Lysosome

• A membrane-bound sac containing lysozymes which carry out intracellular digestion of old/damaged organelles and debris.

• Found in animal cells

Chloroplasts

• They are the site of photosynthesis where plants make glucose using light, CO2 and water.

• found in most plant cells

chloroplasts properties

an oval shaped structure contain green pigment called chlorophyll. inside are thylakoid discs, which are stacked together to form grana. the thylakoid membrane is surrounded by a fluid called the stroma.

Central Vacuole

• a liquid filled sac surround by a membrane called the tonoplast, which stores water, salts, sugars, amino acids and metabolic wastes

Plant Cell Wall

• made of a sugar called cellulose which provides structural support for the cell, enabling the cell to maintain shape.

• it surrounds the plant cells, outside the plasma membrane

Starch Grain

colourless, oval shaped structures which store glucose as starch.

central vacuole properties

• found in most plant cells, take up majority of space and assists with cell rigidity due to high water pressure

plasma membrane properties

a few nanometres thick, is a flexible structure, differentially permeable to certain molecules

phospholipid

the main component of a cellular membrane which consists of a glycerol molecule connected on one side by two fatty acid chains and on the other a phosphate group

phospholipid bilayer

a structure formed by phospholipids in water where the hydrophilic phosphate head faces outwards and the hydrophobic tail face inward creating a self-assembling, self healing bilayer that makes the cell membrane

hydrophilic head

the phosphate end of the molecule that is attracted to water, which is orientated faces outwards, made of phosphate and glycerol

hydrophobic tail

the fatty acid end of the molecule that is not attracted to water, in which they are orientated inwards, made of fatty acid

fluid mosaic model

a way of describing the cell membrane as a flexible layer with moving molecules that give it fluidity and a mosaic-like appearance.

membrane molecules

cholesterol, integral proteins, peripheral proteins

cholesterol

keeps the membrane stable when temperatures fluctuate and is partly hydrophilic and partly hydrophobic

integral proteins

they span the bilayer and often have a role in the transport of substances across the membrane

peripheral proteins

proteins that appear on one side of the bilayer which helps with cell signaling, support and communication

other membrane molecules

involved in the adhesion and communication between cells, with receiving signaling molecules as well as other roles

passive

not requiring energy

active

requiring energy

differentially permeable

only certain substances can pass through

diffusion

describes the passive movement of a molecule down a concentration gradient

concentration gradient

a difference in concentration between two regions

simple diffusion

occurs through the phospholipids of the membrane bilayer

equilibrium

reached when the net concentrations of a molecule on each side of the membrane are equal, where molecules keep moving back and forth but net movement stops

Can pass through lipid bilayer

oxygen, carbon dioxide, and other lipid-soluble molecules or small uncharged particles

Cannot pass through bilayer without assistance of proteins

ions (na+) and large water-soluble molecules (glucose)

facilitated diffusion

where the diffusion of ions, water-soluble or large molecules is aided across the membrane by a specific transport protein

channel proteins

form narrow hydrophilic pores through which substances can diffuse rapidly (channel does not move)

carrier proteins

change shape as they assist the transport of a substance to the other side of the membrane via diffusion. Once transport is complete the original shape of the carrier protein is restored

osmosis

the passive net movement of water molecules across a differentially permeable membrane from a region of low solute concentration to one of high solute concentration.

aquaporins

water moves into and out of cells through specific membrane proteins called aquaporins, however some can pass directly through bilayer due to their small size

isotonic environment

when the extracellular fluid has the same concentration of solutes as the intracellular fluid. a cell maintains normal shape, and there is no net movement of water across the membrane

hypotonic environment

when the extracellular environment has a lower solute concentration than the cell. water will enter the cell. water moves in

hypotonic environment in animal cell

this causes lysis where the cell bursts because its membrane cannot withstand the internal water pressure

hypertonic environment

where the extracellular environment has a higher solute concentration than the cell. the cell will lose water. can lose its ability to function if it becomes severely dehydrated (shrivels)

flaccid

when a plant cell is placed in a hypertonic solution and it loses water because the central vacuole collapses

plasmolysis

occurs when so much water is lost that the plasma membrane shrinks away from the cell wall