Cells

Foundational Concept 2: Highly-organized assemblies of molecules, cells, and organs interact to carry out the functions of living organisms

Transport across a cell membrane

2A: Each cell in your body has a “membrane potential.” Think of it like rolling a ball to the top of a hill - once the ball is at the top, it is smooth sailing down. Similarly, this electric membrane potential allows ions to flow down a gradient of electrical energy (the inside of the cell is negative relative to the outside). We will discuss this concept as well as other mechanisms for movement of ions, water, and other molecules across cellular membranes.
Exercise
Transport across a cell membrane questions
Transport across a cell membrane questions
Article
Passive transport and active transport across a cell membrane article
11:50
How do things move across a cell membrane?
5:16
Passive Transport by Facilitated Diffusion
18:59
Diffusion and osmosis
Learn about diffusion, osmosis, and concentration gradients and why these are important to cells.
7:18
Glomerular filtration in the nephron
13:53
Sodium-potassium pump
How a sodium potassium pump can maintain a voltage gradient across a cell or neuron's membrane.
14:13
Secondary active transport in the nephron
Secondary active transport in the nephron.
8:59
Endocytosis and Exocytosis
Article
Phagocytosis
8:45
Membrane potentials - part 2
Find out how a cell that is permeable to one ion can become charged (either positive or negative) if there is permeability and a concentration gradient. Rishi is a pediatric infectious disease physician and works at Khan Academy.
8:22
Membrane potentials - part 1
Find out how a cell that is permeable to one ion can become charged (either positive or negative) if there is permeability and a concentration gradient. Rishi is a pediatric infectious disease physician and works at Khan Academy.
12:42
Permeability and membrane potentials
Find out why a cell that is permeable to multiple ions has a membrane potential that is influenced by the ion with the highest permeability. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Cell theory

Let’s go on a journey that starts with Robert Hooke and Anton van Leeuwenhoek hunched over their microscopes looking at cork and bacteria, respectively. These videos will guide you through the events that led us to the knowledge we have today about cells.
Exercise
Cell theory questions
Cell theory questions
11:14
History and development of cell theory

Eukaryotic cells

Unlike prokaryotes, eukaryotic cells have a nucleus and other membrane-bound organelles that allow the cell to compartmentalize different functions. These videos will provide an overview of eukaryotic cells and will take you through the structures and functions of the various organelles found within the plasma membrane.
Exercise
Eukaryotic cell questions
Eukaryotic cell questions
Article
Cellular organelles and structure
8:55
Characteristics of eukaryotic cells
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
6:05
The nucleus
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
15:11
Mitochondria
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
9:41
Endoplasmic reticulum and golgi apparatus
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
5:43
Lysosomes and peroxisomes
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
7:20
Epithelial and connective tissue
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.

Cytoskeleton

The cytoskeleton provides an internal framework for the cell, much like our skeleton helps support our body. In these videos, you will learn about the different filaments that comprise the cytoskeleton, and how these filaments provide structural support, create roadways for intracellular transport, and generate cellular motion.
Exercise
Cytoskeleton Questions
Questions pertaining to Cytoskeleton
6:28
Introduction to cytoskeleton
13:04
Microfilaments and intermediate filaments
3:27
Microtubules

Prokaryotes/bacteria

When you think about prokaryotes, disease-causing bacteria might come to mind. However, most prokaryotes are not harmful. Prokaryotes live symbiotically with many plants and animals and are key players in the global ecosystem. They are incredibly diverse and are found in the most extreme of environments. These videos will take you through a general overview of these amazing organisms.
Exercise
Prokaryotes Questions
Questions pertaining to Prokaryotes
7:41
Overview of Archaea, Protista, and Bacteria
7:25
Bacterial characteristics - Gram staining
6:59
Bacterial reproduction - Bacterial growth curve
4:26
Bacterial genetic recombination

Viruses

Viruses can cause sickness and disease, however they are not living entities. If they are not alive, then what are they? In this section, you will learn about the different types of viruses and how they survive, replicate, and spread inside a host organism.
Exercise
Virus structure and reproductive cycle questions
Questions pertaining to virus structure and reproductive cycle
Article
Are viruses dead or alive?
11:05
Virus structure and classification
5:11
Viral replication: lytic vs lysogenic
7:28
Retroviruses
5:01
Subviral particles: viroids and prions

Cellular division

Exercise
Cellular division questions
Cellular division questions
5:43
Cell cycle phases
Learn about the different "seasons" of a cell's life and how it grows with time. By Raja Narayan. Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
4:09
Cell cycle control
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
3:45
Loss of cell cycle control in cancer
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
10:27
Fertilization terminology: gametes, zygotes, haploid, diploid
How haploid gametes (sperm and egg cells) combine to form a diploid zygote with two sets of chromosomes.
9:35
Zygote differentiating into somatic and germ cells
Learn how a zygote, the single cell produced by fertilization, divides by mitosis to produce all the tissues of the human body (including germ cells, which can undergo meiosis to make sperm and eggs).
Article
Mitosis and meiosis
8:28
Interphase
Interphase of the cell cycle, including G₁, S, and G₂ phases.
12:12
Mitosis
Phases of mitosis: prophase, metaphase, anaphase, and telophase.
5:51
Comparing mitosis and meiosis
Comparison of the processes of mitosis and meiosis.
9:45
Phases of meiosis I
How homologous chromosomes separate into two sets. Prophase I, metaphase I, anaphase I, and telophase I.
10:58
Phases of meiosis II
How sister chromatids separate to form gametes. Prophase II, metaphase II, anaphase II, telophase II.
19:54
Embryonic stem cells
An overview of early development of a zygote to an embryo. Embryonic and somatic stem cells.
12:36
Cancer
An introduction to what cancer is and how it is the by-product of broken DNA replication.

Cellular development

What is the difference between a heart cell and a liver cell? Not only do they look different, but they obviously have different roles in our bodies. Yet, both of these cells have the same 23 chromosomes in their nuclei, so shouldn’t they be similar? These videos explain why a heart cell becomes a heart cell and not a liver cell.
Exercise
Cellular development questions
Questions pertaining to cellular development
11:54
Stem cells
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
6:37
Cellular communication
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
11:32
Mitochondria, apoptosis, and oxidative stress
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
8:31
Cellular specialization (differentiation)
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
10:53
Telomeres and cell senescence
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.
7:34
Cellular movement
Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video.

Embryology

Do you remember when you were just a sperm and an egg, or when you were just made up of 32 cells, or when you were a blastocyst attaching to your mom’s uterus? These videos should help jog your memory about the nine months before you came into this world as an human being.
Exercise
Embryology questions
Questions pertaining to Embryology
Exercise
Embryology questions 2
Questions pertaining to embryology
Article
Egg meets sperm
11:35
Egg, sperm, and fertilization
Article
Human embryogenesis
12:20
Early embryogenesis - Cleavage, blastulation, gastrulation, and neurulation
4:50
Implantation
4:25
Gestation
2:11
Germ layer derivatives