Cells

Cell Theory

1. All living things are composed of cells.

2. The cell is the smallest functional unit of life.

3. New cells come from division of preexisting cells.

Prokaryotic Cell

The oldest and simplest (unicellular) type of cell. Does not store DNA in nucleus, because it doesn’t have one. Does not have membrane-bound organelles.

Eukaryotic Cell

Have DNA in the form of chromosomes in a nucleus and have membrane-bound organelles.

Nucleus

The control center of the cell. Stores cell’s DNA and contains instructions for the traits of organisms and construction of proteins. Has a porous nuclear envelope, allowing proteins, RNA, and other molecules to move from nucleus into cell.

Cytoplasm

Area outside the nucleus that contains the cell organelles and where the nucleus’ instructions are carried out.

Rough Endoplasmic Reticulum

Covered with ribosomes which are responsible for assembling proteins.

Smooth Endoplasmic Reticulum

Makes membrane lipids and detoxifies drugs.

Golgi Apparatus

Modify, sort and package proteins from the rough ER for storage in the cell or export outside the cell.

Lysosomes

Organelle filled with enzymes that allow it to digest proteins, lipids, and carbs into smaller molecules.

Vacuoles

Stores water, proteins, and carbohydrates.

Mitochondria

Enclosed by two membranes and is the site of cellular respiration. Converts chemical energy stored in food into an energy compound the cell can use (ATP).

Chloroplasts

Contains chlorophyll and captures energy from sunlight to convert it into chemical energy (photosynthesis).

Cytoskeleton

Network of protein filaments that helps maintain cell shape and aid in movement.

Microtubules

Hollow structures like centrioles in animal cells.

Cell Membrane

All cells have this and it regulates what enters and leaves the cell, i.e. selectively permeable. Provides support and protection and keeps the cell in homeostasis.

Phospholipid Bi-layer

A flexible, double-layered sheet that has proteins embedded which allow it to act as channels and pumps that move materials across the membrane. Carbohydrates attached to the proteins act as ID cards, allowing them to be identified.

Factors That Affect Membrane Permeability

Size, solubility in lipids, ion charge, and presence of carrier proteins. “Large and Charged”

Simple Diffusion

A passive process involving the movement of molecules from an area of high concentration to low; occurs because of constant molecular movement and collision.

Facilitated Diffusion

A passive process where carrier proteins assist the diffusion of materials, e.g. glucose.

Osmosis

The movement of water through a selectively permeable membrane from low to high solute concentration.

Hypertonic

High solute concentration outside of cell so water moves from the inside to outside cell (follows solute).

Hypotonic

High solute concentration inside cell, so water moves from outside to inside cell.

Isotonic

Same concentration so water moves in both directions equally.

Active Transport

An active process that includes the movement of molecules (atoms) against the concentration gradient (from low to high). Carried out by membrane proteins (pumps), i.e. sodium potassium pump.

Endocytosis

Surrounding a substance with some of the cell membrane and then, bringing it into the cell, within a vacuole.

Phagocytosis

Endocytosis for solidos

Pinocytosis

Endocytosis for liquids.

Exocytosis

The reverse of endocytosis, the removal of a substance through a vacuole.

Cell Wall

Cell walls are found in plants, algae, fungi, and many prokaryotes. It provides support and protection for the cell.

Surface Area to Volume Ratio

The more surface area ta the same volume allows for a better exchange of materials, i.e. nutrients, wastes, oxygen, CO₂, and water. Diffusion pathways are shorter and are thus more efficient.

Why Do Cells Divide?

Growth of organisms, SA:Vol, and to replace dead / damaged cells.

Mitosis

The division of nucleus (DNA); occurs in eukaryotic somatic (non-reproductive) cells.

Cytokinesis

Duplication and division of the cytoplasm.

Chromosomes (DNA)

Carry all the genetic information (traits) for the organism in the bases of the DNA. They are made of chromatin (DNA twisted around histone proteins). Chromatin coils to form chromatid.

Interphase

The longest part of the cell cycle. The cell’s nucleus and nucleolus are clearly visible and chromosomes have not appeared.

G₁ (First Gapphase)

Cell growth; right after cell division. Prepares to replicate DNA.

S (synthesis) Phase

DNA replicates.

G₂ (Second Gapphase)

Replication of cell organelles (to prepare for division) and synthesis of other cell components.

Prophase

Nuclear membrane, nucleus, and nucleolus start to disappear. Spindle fibers and centrioles appear (plants don’t have centrioles) and chromosomes are clearly visible.

Metaphase

Chromosomes are lined up at the center of the cell (metaphasoplate) after attaching to the visible spindle fibers.

Anaphase

The chromosomes (sister chromatids) are pulled (at the centromeres) to the opposite poles of the cell. Each chromatid is now a single chromosome and each side gets an exact copy of each chromosome.

Telophase

Nuclear membrane, nucleus, and nucleolus reappear. Chromosomes and spindle fibers start to disappear, and mitosis is complete at this point.

Cytokinesis

The division of cellular organelles and cytoplasm, in plant cells, the Golgi Apparatus (body) secrete a cell plate in the middle of the cell.