AP Biology - Cell Structure and Function

Surface area-to-volume ratio

There needs to be space for the cell to make exchanges from the inside of the cell to the outside and vice versa.

Prokaryotic cells

Simple cells, bacteria + archaea. Have cytoplasm, nucleoid, ribosomes. Some have cell wall, plasma membrane, flagella and a capsule. The only membrane is the plasma membrane.

Light microscopes

These can magnify the size of an organism up to 1000 times. Ex: compound microscopes in labs.

Electron microscopes

Can see the detailed parts of a cell

Eukaryotic cells

Complex cells, fungi, protists, plants, animals. Have organelles.

Plasma Membrane

Made up of a phospholipid bilayer. Regulates the movement of material in and out of the cell. Has some proteins inserted in it.

Phospholipid Bilayer

The hydrophobic fatty acid tails are on the inside and the hydrophilic phosphate heads are on the outside.

Peripheral Proteins

Proteins found on the inner or outer part of the membrane.

Integral Proteins

Amphipatic proteins bound to plasma membrane. Hydrophilic bits extend out of the cell or into the cytoplasm, whereas hydrophobic parts are with the fatty acid tails.

Transmembrane Proteins

Integral proteins that go all the way through the membrane

Fluid-Mosaic Model

Each layer of phospholipids can move and it has different proteins + carbohydrate chains going through the membrane.

Adhesion Proteins

Form pathways between cells

Receptor Proteins

Places for items to land to arrive into the cell

Transport Proteins

These pump solutes using ATP across the cell membrane

Channel Proteins

Protein that channels certain molecules through the cell membrane

Cell Surface Markers

Help the cell recognize other cells and bond to other cells

Carbohydrate Side Chains

Attached to some proteins, only on the outside of the cell membrane

Nucleus

Typically largest organelle in the cell. Gives instructions for the cell to reproduce. Home of DNA, where it is organized into chromosomes, also has the nucleolus where ribosomes are made.

Chromosomes

How DNA is organized within the nucleus

Nucleolus

Produces ribosomes from ribosomal RNA (rRNA)

Ribosomes

Place where proteins are made. There are two subunits, large one + small one. Made up of rRNA + proteins, can either be free floating or attached to endoplasmic reticulum

Endoplasmic Reticulum

Helps with transport within the cell. Is continuous channel. Divided into rough and smooth sections.

Rough Endoplasmic Reticulum

Attached to the nucleus, has ribosomes in it. Typically proteins are made there and then shipped across the cell.

Smooth Endoplasmic Reticulum

No ribosomes, makes lipids, hormones, steroids + decomposes toxic chemicals

Golgi Complex

Helps process proteins. Packages products in vesicles, then distributes. Also helps producing lysosomes. The structure looks like stacks of flattened sacs

Vesicles

Little sacs that the final products of the golgi complex get packaged in.

Mitochondria

Often said to be the powerhouse of the cell. Produces ATP, has two membranes and the inner membrane has cristae. Most of ATP production done in the cristae.

adenosine triphosphate

Most common energy molecule in the cell, also known as ATP

Cristae

Folds in the inner membrane, where most ATP production happens

Lysosomes

Carry digestive enzymes inside them, which they can use to destroy things that are no longer important to the cell. Also helpful in apoptosis

Apoptosis

Programmed cell death

Centrioles

Small cylindrical structures that are in pairs that are typically found within microtubule organizing centers. During cell division, these produce microtubules, which pull apart the replicated chromosomes

Microtubule Organizing Centers

Also known as MTOCs, where centrioles are found.

Vacuoles

Fluid-filled sacs that store water, food, wastes, salts or pigments. Have lots of functions in plant cells.

Peroxisomes

Detoxify certain things and produce hydrogen peroxide while detoxifying. Can also break down hydrogen peroxide into oxygen + water. Common in kidneys + livers in animal cells.

Cytoskeleton

Shape of cell is determined by this. Structure of protein fibers

Microtubules

Made up of protein tubulin, help with centroiles, cilia + flagella.

Microfilaments

Made up of protein actin. The monomers of actin are broken and apart and rejoined to help these grow/shrink. These help during cytokinesis, muscle contraction + formation of pseudopodia extensions while the cell’s moving.

Cilia

Small furs that help organisms move

Flagella

Whiplike structure that helps organisms move

Euglena

Moves due to its flagella

Paramecium

Moves due to its cilia

Cell Wall

Made up of cellulose, only occurs in plant, protists, fungi + bacteria, outside of plasma membrane. In fungi, made out of chitin

Chitin

Modified polysaccharide, what fungi’s plant walls are made out of.

Chloroplasts

Double membrane, have chlorophyll, which makes them green

Central Vacuole

The largest organelle in the plant cell

Cell Sap

What fills the central vacuole and should be present in mature plants

Homeostasis

How organisms keep a stable environment

Semipermeability of plasma membrane + size and charge of the particles wanting to get across

What does the ability of molecules to move across the cell membrane depend on?

Facilitated Transport

What a substance uses to cross the cell membrane if it is hydrophilic. Falls under passive transport. Needs channels to let the molecules move through the membrane

Aquaporins

Channels that are only used for water

Simple Diffusion

If molecule is hydrophobic, just drifts through the cell membrane.

Facilitated Diffusion

When a channel protein or something similar is required in order for a molecule to get through the cell membrane

Passive Transport

Whenever a molecule is moving through diffusion, no actual energy going into the process

Osmosis

Water diffusing through the cell membrane. Water wants to move from a place with high concentration to low concentration. Solvent moves towards equilibrium.

In diffusion, the membrane is permeable to solute, in osmosis, it isn’t

What is the key difference between diffusion and osmosis

Tonicity

The water gradients

Isotonic

Solute concentration is the same on both sides of the membrane

Hypertonic

Higher solute concentration outside the cell

Hypotonic

Lower solute concentration outside the cell

Water Potential

Also known as Ψ, measure of potential energy in water. Two different factors that affect it, pressure potential and solute potential

It lowers the water potential, which means that water is less likely to leave the solution and water is more likely to add to the solution

What does adding a solute do to the water potential of a solution?

Active Transport

Movement of the solute from the location with lower solute concentration to the location with higher solute concentration.

Sodium-Potassium Pump

Takes out 3 sodium ions, brings in two potassium ions. Uses ATP to move ions across the cell membrane

Primary Active Transport

Directly moves something uses ATP

Secondary Active Transport

Whenever something is transported using the energy generated by the movement of another substance

Resting Membrane Potential

Difference in charge between the inside and outside of the cell. The inside of the cell is always a little negative

Endocytosis

Whenever molecules that want to get into the cell are too big, so the entire cell engulfs the molecule, by the cell membrane forming a pocket, which will turn into either a vesicle or a vacuole.

Pinocytosis

Cell takes in liquids through endocytosis

Phagocytosis

Cell takes in solids through endocytosis

Receptor-Mediated Endocytosis

When a molecule attaches to a receptor, then the cell membrane folds around the receptor and the molecule and brings the molecule into the cell

Clathrin

Protein which lines endocytic pits.

Bulk Flow

Transport into the cell that comes because of pressure

Dialysis

Diffusion of solutes across a membrane that selects what to get through

Exocytosis

When a cell ejects something out, reverse endocytosis