cell biology review

Cell Theory

The theory that states all living things are composed of cells, the cell is the basic/smallest unit of life, and all cells come from pre-existing cells.

Inductive Reasoning

A type of reasoning where specific observations are used to form a general conclusion, as seen in the development of the cell theory.

Deductive Reasoning

A type of reasoning that uses a general premise to form a specific conclusion, allowing predictions about newly discovered organisms based on cell theory.

Total Magnification

The calculation of the microscope's total magnification, given by the formula TOTAL MAGNIFICATION = OCULAR × OBJECTIVE.

Microscopy Skills

Skills that include making temporary mounts of cells and tissues, staining, measuring sizes, focusing with coarse and fine adjustments, and calculating actual size and magnification.

Subcellular Components

Parts of a cell that are not alive and do not perform the functions of life.

Living Organisms

All living things that are composed of cells.

Basic Unit of Life

The cell, which is the smallest unit that can perform all life processes.

Spontaneous Generation

The concept that cells can arise from non-cellular matter, which has been disproven as all cells come from pre-existing cells.

Evidence Supporting Cell Theory

Biologists have observed that all forms of life contain at least one cell and that subcellular components do not perform life functions.

Microscope Focusing Steps

1. Center the slide under the objective lens. 2. Use the lowest power objective lens. 3. Adjust the coarse focus knob to bring the stage up. 4. Adjust light source and diaphragm. 5. Use fine adjustment for perfect focus.

Mechanical Stage Controls

Controls used to move the microscope slide to center the image in the field of view.

Ocular Lens

The lens you look through in a microscope, which contributes to total magnification.

Objective Lens

The lens on a microscope that is closest to the specimen, which also contributes to total magnification.

Coarse Focus Knob

The knob used to make large adjustments to the focus of the microscope.

Fine Focus Knob

The knob used for making small adjustments to the focus of the microscope.

Light Source

The part of the microscope that provides illumination for viewing the specimen.

Diaphragm

The part of the microscope that controls the amount of light reaching the specimen.

Temporary Mounts

Preparations made to observe cells and tissues under a microscope.

Staining

The process of applying dyes to specimens to enhance contrast in microscopy.

Eyepiece Graticule

A measuring device used in the eyepiece of a microscope to measure the size of specimens.

Scale Bar

A graphical representation used in microscopy images to indicate the size of the specimen.

Photographs in Microscopy

Images taken through a microscope to document observations of specimens.

Predictions from Theories

Using deductive reasoning to make predictions about characteristics of newly discovered organisms based on established theories.

Cell Theory Predictions

The ability to predict that a newly discovered organism consists of one or more cells based on cell theory.

Temporary wet mount

A method to prepare and stain a microscopic sample for observation.

Cell structures drawing

The process of illustrating cell structures seen with a microscope using sharp, carefully joined lines and straight edge lines for labels.

Drawing Materials

All drawings should be done with a sharp pencil line on white, unlined paper. Diagrams in pen are unacceptable because they cannot be corrected.

Positioning

Center drawing on the page. Do not draw in a corner to leave room for labels.

Size

Make a large, clear drawing; it should occupy at least half a page.

Labels

Use a ruler to draw straight, horizontal lines. The labels should form a vertical list and be printed (not cursive).

Technique

Lines are clear and not smudged. Avoid 'feathery' pencil lines and gaps. Do not include shading or coloring.

Scale

Include a labeled scale bar that indicates estimated size of the sample, with the correct number of digits and unit.

Accuracy

Draw what is seen; not what should be there. Avoid making 'idealized' drawings and only show what is necessary for understanding.

Field of view diameter measurement

Measure the field of view diameter of a microscope under low power.

Method 1 for measuring field of view

Place a transparent metric ruler under the low power objective lens of a microscope to measure the diameter of the field of view on low power magnification.

Final written number

Any measurement should have only ONE estimated value in the final written number.

Title of drawing

The title should state what has been drawn and what lens power it was drawn under, for example, phrased as: drawn as seen through 400X magnification.

Title formatting

Title is informative, centered, and larger than other text. The title should always include the scientific name (which is italicized or underlined).

Drawing clarity

Avoid making unnecessary reproductions of the entire contents of a microscopic field; focus on essential details.

Low power plans

When drawing low power plans, do not draw individual cells; show only the distribution of tissues.

High power drawings

When making high power drawings, draw only a few representative cells and indicate thickness of walls, membranes, etc.

Labeling technique

Labels should be printed clearly and not cursive.

Drawing size requirement

Drawings should occupy at least half a page to ensure clarity.

Ruler use for labels

Use a ruler to ensure straight lines for labels.

Drawing correction

Diagrams in pen are unacceptable because they cannot be corrected.

Field of view diameter

The diameter of the field of view under high power often cannot be measured directly and must be calculated using an equation.

Magnification

Magnification = Image Size / Actual Size

Quantitative observations

Measurements (Magnification, Image size, Actual Size)

Qualitative observations

Cell drawings

Resolution

The smallest interval distinguishable by the microscope, which corresponds to the degree of detail visible in an image created by the instrument.

Magnification (definition)

How much larger an object appears compared to its real size.

Compound Light Microscope

Uses multiple lenses to bend light and magnify images.

Benefits of Compound Light Microscope

Ease of use, less expensive to buy, can observe dead or living cells in color, cell movement can be studied, quick specimen preparation (minutes to hours), no need for high voltage electricity.

Limitations of Compound Light Microscope

Maximum magnification of about 1500X, low resolving power (0.25µm to 0.3µm).

Electron Microscope

Uses electron beams focused by electromagnets to magnify and resolve.

Benefits of Electron Microscope

Magnification of 100,000X to 300,000X, high resolving power (0.001µm).

Limitations of Electron Microscope

Expensive to use, requires cells to be killed and chemically treated, no movement can be seen, without stain or dye, no color can be seen, high voltage electric current is required, specimen preparation usually takes few days.

Fluorescent stains

Generate particularly bright images to visualize cell structures.

Immunofluorescence

A technique that uses fluorescently stained antibodies to bind to specific target proteins within a cell.

Freeze-fracture

A technique that involves rapid freezing of cells and then fracturing them along lines of weakness, including through the center of membranes.

Cryogenic electron microscopy

An electron microscopy technique used to determine the structure of molecules at near atomic-level resolution by freezing a solution with the molecule of interest and bombarding it with a beam of electrons.

Typical cells

Have DNA as genetic material and a cytoplasm composed mainly of water, enclosed by a plasma membrane composed of lipids.

Plasma membrane

Every cell has a membrane barrier separating the interior from its surroundings. The membrane is a bilayer formed from phospholipids as a consequence of their hydrophobic and hydrophilic regions.

Cytoplasm

Cytoplasm is the gelatinous liquid that fills the inside of a cell. It is composed of water, salts, and various organic molecules. These dissolved substances are needed to carry out the metabolic processes required to keep the cell alive.

DNA

All living organisms use DNA as the genetic material.

Ribosomes

In both prokaryotes and eukaryotes, ribosomes catalyze the synthesis of polypeptides. Prokaryotes have smaller (70s) ribosomes, while eukaryotes have larger (80s) ribosomes.

Cell wall

Provides structure and prevents the cell from bursting when it takes up water.

Nucleoid

Main DNA of the cell, found freely in the cytoplasm, not enclosed in a membrane. DNA is a single loop and is not wrapped around proteins (termed 'naked').

Naked DNA

Prokaryotic cell DNA is 'naked,' which means that the DNA is not associated with proteins.

Homeostasis

All life has a maintenance of homeostasis. Living organisms keep their internal environments within a certain range despite changes in their external environment.

Metabolism

The set of life-sustaining chemical reactions in organisms.

Nutrition

The process of obtaining food necessary for health and growth.

Movement

The ability of an organism to change its position or location.

Excretion

The process of removing waste materials from the body.

Growth

The process of increasing in physical size.

Response to Stimuli

The ability of an organism to respond to changes in its environment.

Reproduction

The biological process by which new individual organisms are produced.

70s ribosomes

Ribosomes found in prokaryotes that are smaller than those found in eukaryotes.

80s ribosomes

Ribosomes found in eukaryotes that are larger than those found in prokaryotes.

Gel-like fluid substance (cytosol)

Mostly water with many dissolved molecules, site of metabolic reactions.

Prokaryotic cell structure

Includes components such as cell wall, plasma membrane, cytoplasm, naked DNA in a loop, and 70S ribosomes.

Gram-positive eubacteria

A type of prokaryotic cell structure required for understanding prokaryote cell structure.

Single loop DNA

DNA in prokaryotes that is not wrapped around proteins and is found freely in the cytoplasm.

Histone proteins

Proteins that DNA wraps around in eukaryotic cells, which is not the case in prokaryotic cells.

Viruses

Lack metabolism, a reason they are not considered to be self-sustaining life.

Enzymes

A type of protein that catalyze metabolic reactions.

External energy sources

Some organisms use these (usually the sun) to synthesize carbon compounds from simple inorganic substances.

Carbon compounds

Some organisms use these obtained from other organisms to synthesize the carbon compounds that they require.

Human excretion

Primarily occurs via lungs and kidneys.

CO2 excretion

Humans breathe out CO2.

Plant excretion

In many plants, excretion occurs via leaves, roots and stem.

Oxygen in photosynthesis

An excretory product of photosynthesis that diffuses out of pores in leaves called stomata.

Unicellular organism excretion

Occurs through the cell membrane.

Chlamydomonas

Single celled organisms that excrete waste via diffusion directly through their cell membrane.

Development

The transformation of the organism through its lifespan.

Single celled organism response

Even single celled organisms can recognize what is going on around them, and respond to changes in the environment.

Sexual reproduction

Involves two parents and the fusion of sex cells from each parent.

Asexual reproduction

Involves only one parent and produces offspring that are all genetically identical to the parent.

Prokaryotic cell structures

Identifiable in light and electron micrographs as nucleoid region, prokaryotic cell wall, nucleus, mitochondrion, chloroplast, sap vacuole, Golgi apparatus, rough and smooth endoplasmic reticulum, chromosomes, ribosomes, cell wall, plasma membrane and microvilli.