Lesson 1 - Life is Cellular

Cell Theory Scientists

Anton van Leeuwenhoek - the first to observe living microorganisms

Robert Hooke - observed a magnified piece of cork, coined the term “cells” to delineate the chambers inside

Theodor Schwann - proposed that all animals are made up of cells

Matthias Jakob Schleiden - proposed that all plants are made up of cells

Cell Theory

1. All living things are made up of cells.

2. Cells are the basic units of structure and function in living things.

3. New cells are produced from existing cells.

Microscopes

1. Light Microscopes - directs how light is reflected/transmitted into the eye to magnify the image seen

2. Electron Microscopes - uses an electron beam to scan or transmit into a specimen. Higher magnification power than light microscopes.

   1. Transmission Electron Microscope (TEM)

      1. Specimen observed cannot be alive, placed into a vacuum

   2. Scanning Electron Microscope (SEM)

      1. 3d

3. Micrograph - a photo of an object seen through a microscope

   1. Electron microscopes do not capture light, so light is not shown in electron micrographs

      1. Scientists may use “false-coloring,” which is editing an uncolored micrograph to show color

Organelles

Nucleus - a membrane that contains DNA

• Nucleolus - creates ribosomes (located in the very core of the nucleus)

• Nuclear pores - holes in the nucleus that ribosomes exit from

• Chromatin -

• Nuclear envelope -

Ribosomes - synthesizes proteins

• Can be free-floating in the cytoplasm

  • Can also make proteins, location/destination is just different

• Or attached; stuck to the rough endoplasmic reticulum

  • Proteins are then carried to the Golgi apparatus in vesicles

Rough endoplasmic reticulum - directly surrounds the nucleus

Golgi apparatus - series of stacked membranes that package and sort proteins

Vacuoles - storage container

• Most plant cells have a large central vacuole

Nucleoid - the region of a prokaryote that contains DNA; not a nucleus

Cell membrane - all cells have these; separates the insides of the cell from the external surroundings

• intracellular space (inside the cellular membrane)

• extracellular space (outside the cellular membrane)

Cytoplasm - all cells have these; the fluids inside a cell (outside the nucleus)

• made up of cytosol with other substances mixed in (sugars dissolved in it, proteins, etc.)

Cytoskeleton - internal framework of the cell

• involved in movement and cell division (for creation of the spindle)

• can be used as an internal highway

• made up of microtubules and microfilaments which are in turn made up of proteins

Chloroplasts - capture energy from sunlight and convert into food that contains chemical energy

• Endosymbiotic theory

Mitochondria - convert chemical energy from food into compounds the cell can use in a process called cellular respiration

Lesson 3 - Cell Transport

The cell membrane works to keep the cell in homeostasis, a consistent state of internal, physical, and chemical conditions an organism maintains. The cytoplasm inside a cell consists of cytosol, in which many other substances are suspended. In order to maintain homeostasis, the particles of these foreign particles should be evenly distributed throughout the cell. To achieve this, a process known as diffusion is carried out.

Diffusion is the process in which particles (usually solutes) move across a membrane. When it is stated that the diffusion is with the concentration gradient (see below paragraphs for more information), that means that the movement is from an area with higher concentration of particles to an area with less concentration of particles. Particles tend to do this because when they collide, they rebound and move off into another direction; in an area with more particles, they are more likely to collide and move away into an area with less particles.

In a cell maintaining homeostasis, there should be an equal concentration of particles inside and outside the cell membrane. This state is called equilibrium. In equilibrium, particles will continue to move across the cell membrane, but in such a way that they remain in equilibrium (because both sides are equally concentrated, the amount of cells leaving one side would equal the amount of cells entering that side). THe state of being in equilibrium, but still in movement, is called dynamic equilibrium.

Water molecules move to maintain homeostasis as well; an equilibrium of the concentration of a solution. This is why if a cell with a high solute concentration is placed in a solution with a lower solute concentration, the solvent part (for example, water) of the solution lower solute concentration will move into the cell so that their solute to solvent ratios are equal. This is why when placed in a hypotonic solution as described above (having a lower solute concentration than the cell placed into it), the cell will usually burst because of all the water entering it, and the cell will shrink when placed in a hypertonic solution. This phenomenon also occurs because the solutes cannot move through the membrane, but water can through aquaporins.

Plasmolysis is when a cell is placed in a hypertonic solution and shrinks away from the cell wall (due to loss of water to the outside solution).

When a plant cell is placed into a hypotonic solution, it will swell as stated above, but will not burst because of its cell wall. Instead, the cell goes into a turgid state and at some point, the turgor pressure within the cell becomes so high that water can no longer enter the cell, therefore working against osmosis. “The central vacuole stores water and maintains turgor pressure in a plant cell.”

There are varied types of diffusion, but can be organized into two groups: passive and active transport. Passive transport in a cell is diffusion in which the particles to not use energy from the cell for movement. Active transport in a cell is diffusion in which the particles do use energy from the cell for movement.

A type of passive transport is facilitated diffusion, in which certain proteins in the cell membrane act as channels or tunnels that “facilitate” the movement of particles across the cell membrane. This makes diffusion much faster; however, facilitated diffusion is specialized to certain molecules.

A specialized example of facilitated diffusion is osmosis. It is difficult for water molecules to pass through the cell membrane through typical diffusion because of the hydrophobic segment of the lipid bilayer. The lipid bilayer is a component of the cell membrane with a hydrophilic (literally “water-loving”) exterior and a hydrophobic (“water-fearing”) interior. In order for water molecules to easily move across the cell membrane, certain proteins called aquaporins perform facilitated diffusion, allowing H2O molecules to move through them with ease.

When asked to predict where water molecules would move in a situation where both sides of the membrane have a solution of sugar and water, the molecules will move towards the area with a higher concentration of solutes (in this case, the sugar is the solute; water is a solvent).

Active transport is used when cells must move particles against the trend of the concentration gradient (“when the concentration of particles is higher in one area than another. In passive transport, particles will diffuse down a concentration gradient…”). Unlike in passive transport, active transport requires energy. Active transport is typically carried out by transport proteins found in the membrane known as protein pumps for smaller particles, and for larger particles is carried out in "processes known as endocytosis and exocytosis...[which] sometimes involves changes in the shape of the cell membrane" (eText: Cell Transport).

In endocytosis, (taking in large particles through active transport), materials are consumed by pockets in the cell membrane that end up breaking off from the membrane into the cytoplasm as a vesicle or vacuole. In exocytosis (ejecting large particles through active transport), materials are released in a similar way; they are taken in by the cell membrane then broken off, but this time are released into the exterior rather than the interior of the cell.

Homeostasis

To maintain homeostasis, unicellular organisms…

1. grow

2. respond to the environment

3. transform energy (cellular respiration, photosynthesis, etc.)

4. reproduce (cell division, etc.)

Specialized Cells

1. Animal cells

   1. Red blood cells

      1. Carry oxygen to other cells and pick up waste CO2

      2. Do this by using hemoglobin, a protein

2. Plant cells

   1. Chloroplasts

      1. Protists (algae) can have this too

   2. Vascular tissue (animals do not have this but they do have a vascular system)

      1. Carries water and food throughout the plant

Levels of organization, least to most

cell → tissue → organ → organ system

ex:

neuron → nerve tissue → brain → nervous system

Cellular Communication

• reflexes, responses, reactions

• communicate by releasing chemicals