Additional Notes Homeostasis and Transport in the Cell

Addresses anchors not previously covered

Anchor A.4.1.3 – Describe how membrane bound cellular organelles (e.g. endoplasmic reticulum, golgi apparatus) facilitate the transport of materials within a cell.

• Proteins are made by the ribosomes on the Rough ER

• Are placed in sacs called vesicles. • The vesicles are then transported to the Golgi

where they are moved along, packaged and modified.

• The vesicles then move to the cell membrane and release the contents or transport the vesicle to another part of the cell where the protein is needed for the cell to function properly.

Anchor: A.4.1.1 – Describe how the structure of the plasma membrane allows it to function as a regulatory structure and/or a protective barrier for a cell.• Recall that the plasma membrane is made of two layers of

phospholipids and proteins.• Selectively permeable – limits entry of certain molecules• Exchange of materials is very specific• Glycoproteins and glycolipids embedded in the membrane act

as antennae to receive chemical messages from other cells• Cells need the correct balance of nutrients and ions, such as

calcium, magnesium, sodium, potassium and hydrogen to maintain homeostasis.

• The membrane regulates gas exchange, water balance, intake of nutrients and elimination of wastes to maintain homeostasis

Not all molecules can dissolve through the membrane easily. Factors that determine if they can move include:

• Polarity of molecule – Polar or nonpolar – Ex. Water and Ethanol are polar

• Size – large or small – Ex. Nonpolar gases that are small such as nitrogen and oxygen

• Electric charge - positive or negative – Ex. Ions H+ or Ca +2

Concentration gradient – the difference in concentrations across a distance – usually the difference on either side of the cell membrane.

• The membrane acts like a dam holding back water.• A great amount of potential energy is held back

behind the membrane just like the water behind a dam has a great potential to rush out if the dam is opened.

• The cell relies on this potential energy of the concentration gradient to get certain things across the membrane.

Anchor A.4.2.1 – Explain how organisms maintain homeostasis (e.g. thermoregulation, water regulation, oxygen regulation.

• Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different.– Vertebrates can regulate their body temperatures in

2 different ways

• Ectotherms – reptiles, fish and amphibians – warm body by absorbing heat from its surrounding. –Aquatic animals have body temperatures close to

the water temp. –Terrestrial (land dwelling) change location to get

more sun/shade as needed. Can’t live in very cold climates

• Endotherms – mammals and birds – have rapid metabolism which generates heat needed to warm body. Also have insulation such as hair, feathers, fat

• Water regulation (osmoregulation) is the control of water concentrations in the bloodstream which controls the amount of water available for cells to absorb. – Kidneys: mammals –

regulates the amount of water in body by adjusting the concentration of various salts in the blood. Also responsible for removing waste products of metabolism

– Contractile vacuoles: unicellular; Paramecium– contracts to squeeze out excess water, salts and CO2

Contractile vacuole

– Spiracles – Insects – openings on abdomen – can open & close

– Stomata – Plants – openings on leaf surface – can open & close

• Oxygen regulation O2 levels must be regulated according to activity level.

Lungs• Muscle contraction of

diaphragm to move air into highly branched tube-like passages• Passages end in millions of

alveoli – increases the surface area for gas exchange. Spread out, alveoli would cover the size of 2 large parking spaces!!

• Book lungs – spiders - similar to alveoli, but in tissue layers that are like pages in a book

– Gills – fish, aquatic worms, crustaceans

–Water contains dissolved oxygen – moves in by diffusion. Carbon dioxide moves out by diffusion.–Highly efficient–Large surface area –

many fine, threadlike filaments.

– Skin – earthworms – slime layer on outer surface – direct exchange – no special organs