Question

unit1: instructional sequence④
how does the structure of cells allow for the different forms of life?
explain how molecules are transported across membranes & identify as passive or active
a. diffusion
b. facilitated diffusion
c. osmosis
d.active transport
e. endocytosis
f. exocytosis
identify the characteristics of a cell membrane.
hydrophilic heads
hydrophobic tails
show diffusion, facilitate diffusion and active transport
label the parts of

Explanation:

Step1: Structure - life relationship

The structure of cells, with features like the presence of organelles, cell - membrane composition, and genetic material, provides the basis for different life - sustaining functions. For example, the presence of a nucleus in eukaryotic cells allows for more complex regulation of gene expression compared to prokaryotes without a nucleus, enabling a wider range of life forms.

Step2: Molecule transport across membranes

a. Diffusion

Diffusion is the passive movement of molecules from an area of high concentration to an area of low concentration across a semi - permeable membrane. It does not require energy input as it follows the concentration gradient. For example, oxygen and carbon dioxide can diffuse across the cell membrane.

b. Facilitated diffusion

This is also a passive process. It uses transport proteins (carrier or channel proteins) to move molecules (such as polar molecules and ions) across the membrane. The molecules still move down their concentration gradient, so no energy is used. For instance, glucose can enter cells via facilitated diffusion.

c. Osmosis

Osmosis is the passive movement of water molecules across a semi - permeable membrane from an area of lower solute concentration to an area of higher solute concentration. It is driven by the water potential gradient and does not require energy.

d. Active transport

Active transport is an energy - requiring process (using ATP) that moves molecules against their concentration gradient, from an area of low concentration to an area of high concentration. For example, the sodium - potassium pump in cell membranes actively transports sodium ions out of the cell and potassium ions into the cell.

e. Endocytosis

Endocytosis is an active process where the cell membrane invaginates to form a vesicle and engulfs substances (such as large molecules, particles, or even other cells) from the extracellular environment. It requires energy for the membrane to move and form the vesicle.

f. Exocytosis

Exocytosis is the reverse of endocytosis. It is an active process where vesicles inside the cell fuse with the cell membrane and release their contents (such as secreted proteins or waste products) to the extracellular environment. Energy is needed for the vesicle - membrane fusion and movement.

Step3: Cell membrane characteristics

The cell membrane is a phospholipid bilayer with hydrophilic heads (attracted to water) and hydrophobic tails (repelled by water). It also contains proteins (integral and peripheral), cholesterol, and carbohydrates. The membrane is semi - permeable, allowing some substances to pass through while restricting others. It is fluid - mosaic in nature, with the components able to move laterally within the membrane.

Step4: Labeling cell parts

(This would require a visual analysis of the provided cell diagram. Without seeing the full details of the diagram, a general answer is given.) The cell parts could include the nucleus (containing DNA), mitochondria (power - house of the cell for energy production), ribosomes (site of protein synthesis), endoplasmic reticulum (involved in protein and lipid synthesis), Golgi apparatus (modifies, sorts, and packages proteins and lipids), lysosomes (contain digestive enzymes), etc.

Answer:

The structure of cells allows for different forms of life through specialized organelles, a semi - permeable membrane for molecule transport, and genetic material for inheritance.
Diffusion, facilitated diffusion, and osmosis are passive transport mechanisms; active transport, endocytosis, and exocytosis are active transport mechanisms.
The cell membrane is a phospholipid bilayer with hydrophilic heads and hydrophobic tails, and is semi - permeable and fluid - mosaic.
The cell parts in the diagram (to be labeled) include nucleus, mitochondria, ribosomes, etc.