Cell Structure & Function Flashcards
What is cell theory
3 main components:
All organisms are made of cells
Cells are the basic units of life
Cells come from pre existing cells that have multiplied
What is the theory of evolution
It suggests that there is a ‘survival of the fittest’ approach, because the ‘fittest’ organisms - those most suited to their environments are the ones that are able to reproduce most successfully, and are more likely to pass on their traits to the next generation
What are cells?
Cells are the smallest structural and functional unit of the human body. They can specialise.
What happens when a group of specialised cells perform a single job?
It forms a tissue
What happens when a group of tissues carry out a particular function in the body?
Forms an organ
What happens when a group of organs which have related functions come together?
It creates an organ system such as the respiratory system
Discuss the relationship between cells, tissues and organs
We start off as one cell, and end up at around 37 trillion. Cells come together and specialise to form tissue such as muscle tissue. When a group of tissues carry out a particular function in the body, it forms organs, and these organs can come together to form organ systems
cells < tissue < organ < organ systems
What are the 4 different types of tissues?
Epithelial tissue
Connective tissue
Muscle tissue
Nervous tissue
What is epithelial tissue?
This consists of tightly packed sheets of cells which cover surfaces - including outside of the body, and inside the body (such as lining body cavities). For example, outer layer of skin and lining of small intestine
It’s main function is for protection, however, at different parts of the body it could serve different purposes
What is connective tissue?
It is the tissue that connects/separates/ supports(in terms of structure) to all the other types of tissue in the body. It is in between other tissues
It consists of cells surrounded by a fluid called the extracellular matrix, which is made up of protein fibres like collagen and fibrin in a solid, liquid substance
It can also help store fat, help move nutrients and other substances between tissues and organs, and also assists in repairing damaged tissue
What is muscle tissue?
This is composed of cells which have the ability to shortern or contract in order to produce movements of the body part. It is essential for keeping the body upright and for it to move
In other words, it is what enables us to move
What are the 3 main types of muscle tissue
Skeletal
Cardiac
Smooth
What is skeletal muscle tissue?
These are muscle tissues attached to bones by tendons, and allows us to control movements. It is striated (striped muscle)
What is cardiac muscle tissue?
It is only found in the walls of the heart. It is also striated, but it an involuntary muscle tissue
The cardiac muscle is responsible for the contractility of the heart and, therefore, the pumping action. The cardiac muscle must contract with enough force and enough blood to supply the metabolic demands of the entire body.
What is smooth muscle tissue?
It is found in walls of blood vessels, as well as walls of the digestive tract, uterus, urinary bladder. It isn’t striated, and it’s involuntary
The role of the smooth muscles is to control the involuntary movement of most organs present in the body. They provide smooth, steady contractions to enable the movement of substances (i.e. food in the digestive tract)
What is nervous tissue?
It is involved in sensing stimuli - external or internal cues - and processing and transmitting information. It consists mainly of two types of cells; neurons / nerve cells and glia cells.
The nervous system regulates and controls body functions and activity.
What do the neurons do?
They are the basic functional unit of the nervous system, and they generate electrical signals to allow neurons to convey info quickly over long distances
What are examples of different organ systems? (12)
Cardiovascular
Digestive
Skeletal
Lymphatic
Endocrine
Integumentary
Muscular
Nervous
Reproductive
Respiratory
Urinary
Immune
What is the cardiovascular system?
Function is to transport oxygen, nutrients, and other substances to the cells and transports wastes, carbon dioxide, and other substances away from the cells; it can also help stabilize body temperature and pH
What is the digestive system?
Function is to process foods and absorbs nutrients, minerals, vitamins, and water
What is the skeletal system?
Function is to support and protects soft tissues of the body; provide movement at joints; produce blood cells; and stores minerals
What is the lymphatic system?
Function is to defend against infection and disease and transfers lymph between tissues and the blood stream
What is the Endocrine system
Function is to provide communication within the body via hormones and directs long-term change in other organ systems to maintain homeostasis
What is the integumentary system
Function is to provide protection from injury and fluid loss and provides physical defense against infection by microorganisms; involved in temperature control
What is the muscular system
Function is to provide movement, support, and heat production
What is the Nervous system
Function is to collect, transfer, and process information and directs short-term change in other organ systems
What is the reproductive system?
Function is to produce gametes—sex cells—and sex hormones; ultimately produces offspring
What is the respiratory system
Function is to deliver air to sites where gas exchange can occur
What is the urinary system
Function is to remove excess water, salts and waste products from the blood and body and controls pH
What is the immune system
Function is to defend against microbial pathogens - disease causing agents and other diseases
Explain how all the organ systems are interlinked.
All organ systems have to work together to keep the body functioning properly. For example, when exercising, the respiratory system and the circulatory system work closely to deliver oxygen to cells to get rid of the CO2 the cells produce. Only when both systems work together can there be successful gas exchange.
On top of this, at all times, the nervous system also sends messages via neurons to various functions of the organ systems –> systems working together well
What is meant by the scale of the body?
Micro, meso, macro levels
What is meant by the complexity of the body?
All systems are interconencted
What is meant by the dynamic nature of the body?
Multiple processes occurring simultaneously
Describe the anatomical position
It involves a person standing still, facing straight with feet pointed forward, as well as palms towards the front
What are the different body directions we need to know? (10)
Superior
Inferior
Anterior
Posterior
Lateral
Medial
Dorsal
Ventral
Distal
Proximal
What are body directions?
These are terms used to describe various parts of the body with reference to other parts. I.e. the head is superior to the feet
What does superior mean for body directions?
Above (e.g. head is superior to the heart)
What does inferior mean for body directions?
Below (e.g. feet are inferior to the head)
What does Anterior mean for body directions?
Toward the front of the body in the anatomical position (e.g. the nose is anterior to the ears)
What does posterior mean for body directions?
Toward the back of the body (e.g. The ears are posterior to the nose)
What does lateral mean for body directions?
Away from the median plane of the body (e.g. the shoulder is lateral to the head)
What does medial mean for body directions?
Toward the median plane of the body (e.g. the head is medial to the shoulder)
What does dorsal mean for body directions?
Equivalent of posterior
What does Ventral mean for body directions?
Equivalent to anterior
What does Distal mean for body directions?
Further away from the core/trunk than another reference point (e.g. elbow is distal to the shoulder)
Note: proximal and distal are only used with limbs, because these limbs could end up changing positions while moving (i.e. not a head)
What does proximal mean for body directions?
Closer to the core/trunk than another reference point (e.g. shoulder is proximal to the elbow)
Note: proximal and distal are only used with limbs, because these limbs could end up changing positions while moving (i.e. not a head)
What are the 3 anatomical body planes?
Transverse
Frontal/ coronal
Sagittal / latteral
What is the transverse plane?
It is a plane which cuts a bit above your waist, and kind of ‘separates’ superior from inferior
(See book for more info)
What is the frontal / coronal plane
It is a plane which cuts horizontally through your body, and kind of ‘separates’ anterior from posterior
(See book for more info)
What is the saggital / lateral plane
It is a plane which cuts vertically through your body, and kind of ‘separates’ medial from lateral
(See book for more info)
What % of a male is made up of fluids?
fluids = 60%
solids = 40%
What % of a female is made up of fluids
fluids = 55%
solids = 45%
Determine the proportions of the total body fluid for intracellular fluid (ICF) and extracellular fluid (ECF)
2/3 of total body fluid is ICF
1/3 of total body fluid is ECF
What are the different components of extracellular fluids?
80% of it is interstitial fluid, and 20% of it is blood plasma
What are the compartments of the body / fluid compartments?
Intracellular fluids and extracellular fluids
Here body fluids can be discussed in their specific fluid compartments
Explain Intracellular fluids (ICF)
It lies within the cell and includes all fluid enclosed in cells by the plasma membrane.
The ICF is ~60% of total water in the human body
It is the principal component of cytoplasm
Fluid volume tends to be stable as the amount of water in living cells is closely regulated
There has to be a balance in ICF, too much fluid or too little are both harmful to the cell
This fluid is located within the cell membrane and contains water, electrolytes and proteins. K, Mg and phosphate are the three most common electrolytes in the ICF
Explain extracellular fluids
It includes body fluid which isn’t contained in a cell.
Accounts for the other 1/3 of the body’s water content. Approx 20% of the ECF is found in plasma.
It can be split up into plasma and interstitial fluid
The primary function of the ECF is the exchange of substances between the cells and the rest of the body. The fluid acts as a medium for the essential exchange of dissolved gases, nutrients, and electrolytes.
The cerebrospinal fluid which bathes the brain and spinal cord are also considered components of the ECF compartment
What is interstitial fluid?
This is the fluid which is between the cells. It doesn’t include blood plasma, because it is just the liquid between cells
Typically formed from the substances that are realeased from the blood capillaries
What is plasma?
Plasma carries water, salt and enzymes. It is the liquid portion of blood. (92% of it is made up of water)
It transports a range of materials, including blood cells, proteins, electrolytes, nutrients etc.
The main role of plasma is to take nutrients, hormones, and proteins to the parts of the body that need it. Cells also put their waste products into the plasma. The plasma then helps remove this waste from the body. Blood plasma also carries all parts of the blood through your circulatory system.
Explain the concept of surface area for organs in the body. Give an example related to lung alveoli and villi/microvilli
In our organs, we need to maximise the surface area. This involves the idea of ‘packing’ where the tissues in the organs are packed closely to create a dense organ, but with high surface area. All these structures get folded up –> still a lot of SA.
For example, although the lung alveoli may seem small, their overall SA is around 100m^2 –> enables good respiration, thus SA is very important for organs
Also, in the guts and kidneys, the villi can help absorb the nutrients and other necessary things due to an increase in surface area –> important
The main idea is that no matter how large (areawise) our various organs are, they can all be packed into a small volume, which forms many of our organs
Explain the importance of surface area to volume ratio of cells.
As the cell gets bigger (radius wise), the S;V ratio decreases due to the volume rising higher than the surface aarea. Thus, the lower S:V ratio makes the exchange of resources and energy harder and harder
S.A. limits how many nutrients can come in. Thus a high S:V ratio ensures that the exchange of resources are done easier / efficiently.
What is an organelle?
It is a subcellular structure that has one or more specific jobs to perform in the cell
What are the different structures/features of a cell and organelles?
Cytoplasm
Plasma membrane / Cell membrane
Nucleus + Chromatin + Nucleolus
Endoplasmic Reticulum (Rough & Smooth)
Ribosomes
Golgi body / Golgi apparatus
Mitochondria
Lysosome
Cytoskeleton (cilia and flagellum)
What is the cytoplasm - what is its function?
It is the jelly like material inside of the cell, where most organelles float in, such as the nucleus, ribosomes etc.
It assists in dissolving solutes (particles in the cell such as carbs and proteins), as well as help moves material around the cell
It also provides support for the cell
What is the cell membrane - what is its function?
It is composed of a bilayer of lipids and proteins.
Lipids are made up of a hydrophilic (phosphate) head and hydrophobic tail. Thus, the lipid heads are attracted to water molecules of both the intracellular and extracellular environments
The cell membrane is semi permeable - only specific materials may enter and exit through pores and protein channels.
The job of the cell membrane is to allow materials to enter/exit the cell. O2 and H2O can simply pass through the bilayer, however larger molecules/charged particles/polar particles may only be able to go through protein channels
Important to note that the cell membrane remains fluid. The lipids and proteins arent locked in place
What is the nucleus - what is its function?
It is the largest and most prominent organelle, and it stores all genetic instructions for manufacturing proteins. It controls cell activity and is considered the ‘control center’
Inside the nucleus, there is chromatin and a nucleolus.
The nucleus is surrounded by a membrane called the nuclear envelope which consists of two adhacent lipid bilayers with a thin fluid space between them
Spanning the nuclear envelope are nuclear pores. These are tiny passageways for the passage of proteins, RNA and solutes between the nucleus and cytoplasm
What is chromatin?
This refers to the long strands of DNA. It holds info to make proteins
What is a nucleolus?
It makes ribosomes through production of RNA. Once synthesised, new ribosomal units exit cell nucleus through nuclear pores
What is the endoplasmic reticulum?
There are two types; smooth and rough ER
It is a system of channels continuing with the nuclear membrane, covering the nucleus and composed of the same lipid bilayer material
It provides passages throughout much of the cell who’s function is transporting, synthesising and storing materials
The winding structure results in a large membranous surface which supports its function
The endoplasmic reticulum (ER) is a dynamic organelle responsible for many cellular functions, including the synthesis of proteins and lipids, and regulation of intracellular calcium levels.
What is the Rough ER - what is its function?
the function of the RER is to receive ribosomes from the nucleus. It’s function is to transport protein making ribosomes.
Once proteins are made, they are enclosed by a vesicle (cellular envelope that is used to transport materials from one place to another), which is then transported to the golgi body
What is the Smooth ER - what is its function?
Meanwhile, the Smooth ER has no ribosomes (hence smooth). It assists in detoxification - breaks down toxins.
It also mainly produces lipids (phospholipids), cholestrol and hormones and steroids. Also making fats
Thus, cells that produce large quantities of hormones such as female ovaries and male testes contain large amounts of smooth ER due to increased hormone production
What are ribosomes - what are the functions?
Created by nucleolus, and is transported to the rough ER. The function of ribosomes are to make proteins (gathers amino acids and connects them into a long chain –> forms proteins)
What is the golgi body/apparatus - what are the functions?
Job is to receive, modify, sort and package proteins in a vesicle so that they can be transported around. It accepts vesicles of proteins from rough ER.
The golgi body makes final changes to the protein, and then the protein created is put in another vesicle and is released, and fuses with the cell membrane and goes where its needed.
Golgi has to distinct sides, each with a different role. One side receives products in vesicles. These products are sorted through the apparatus and released and repackaged in a new vesicle out the other end.
The vesicle migrates to cell surface and fuses to cell membrane where the ‘cargo’ is secreted
What is the mitochondria - what is its purpose?
Purpose is to create ATP in a process called cellular resipiration (used for energy)
It contains its own DNA
Consists of outer and inner lipid bilayer membrane
Oxygen required for cellular respiration
What are lysosomes - what is its purpose?
Contains powerful digestive enzymes. Jobs include to break down food (i.e. protein broken into amino acids)
Highly acidic organelle for waste breakdown and disposal
It also works to kill pathogens (white blood cells)
Has the option to do autolysis which basically destroys the dying cell (or for damage cells)
What is the cytoskeleton?
Like the bony skeleton supports the human body structurally, the cytoskeleton helps cells maintain structural integrity. Fibrous proteins provide structural support
This is necessary for cell motility (cell migration), cell reproduction and transport of substances within the cell
Three types of protein based filaments:
microfilaments
Intermediate filaments
microtubules
What are microtubles?
These are the thickets of all the protein based filaments, and it maintains cell shape + structure and resists compression of the cells, and plays a part in positioning the organelles within the cell. They also make up the cilia and flagellum which are responsible for movement of cells
What are flagella / flagellum?
This is larger than cilia, and is specialised for cell locomotion. This includes the sperm cell that must propel itself
What is cilia?
There are numerous of them in each cell. They have short hair like extensions
Found on many cells of the body, including epithelial cells that line the airways of the respiratory system. They move rhythmically, beat constantly and move waste such as dust, mucus and bacteria up the airways
What are microfilaments?
This is a thinner shape of cytoskeletal filament. Actin which is a protein that forms chains in the primary component of the microfilaments.
Responsible for muscular contraction
What are intermediate filaments?
These are intermediate in thickness between microtubules and microfilament. It is made up of a protein called keratin which are wound together. Responsible for maintaining cell shape and structure. These RESIST tension
How can a unicellular organism survive and function in isolation?
This is through performing the tasks needed for survival by itself. I.e, functions of life:
Metabolism
Growth
Nutrition
Response
Reproductive
Homeostasis
Excretion
An example of this is a paramecium
How can a paramecium survive in isolation?
This is because it can do the functions of life by itself. For example, excretion is controlled by plasma membrane which controls entry and exist of substances, including expulsion of waste
Nutrition is controlled by food vacules which contain the organisms paramecium consumes
Metabolic pathways happen in cytoplasm
Growth, after consuming biomass from food, it gets larger until it divides
What is diffusion
It is when the net movement of a substance travels down its concentration gradient.
What does it mean to travel down a concentration gradient? Give an example
A substance will move from a high concentration to a low concentration (mainly for water)
Whenever a substance exists in greater concentration on one side of a semipermeable membrane, any substance that can move down its concentration gradient will do so
I.e. O2 generally diffuses into cells because its more concentrated outside of them, and CO2 typically diffuses out of cells because it is more concentrated inside of them.
What happens to net movement at equilibrium?
Equal to zero
What is passive transport?
Passive transport is a type of membrane transport that does not require energy to move substances across cell membranes
What is active transport?
the movement (as across a cell membrane) of substances from regions of lower concentration to regions of higher concentration by the use of energy.
In other words, it requires ATP/energy to move a substance across a membrane, against the constant gradient
I.e. against the concentration gradient
Is diffusion a passive or active transport?
It is passive transport because it is going down the gradient
What are factors affecting diffusion rate?
Distance (Increased distance –> decreased diffusion rate)
Temp (Increased temp –> increased diffusion rate)
Characteristics of solvent (dense solvent –> decreased diffusion rate)
Characteristics of substance travelling (mass increased –> decreased diffusion rate)
WHat is osmosis?
It is the diffusion of water through a semipermeable membrane like cells. It works through passive transport.
Thus, high water concentration –> low water concentration
Note:
High water concentration = low solute concentration
Low water concentration = high solute concentration
Thus, the water tends to also go from a low solute concentration to a high solute concentration
How can water travel through membranes?
Simple osmosis in lipid bilayer or through aquaporins
What are aquaporins?
These are known as water channels. They only allow for water not any othe ion to go into them. It is the main method for water to move in and out of a cell. They are integral membrane proteins, and form pores in the cell membrane
They can also assist in minimizing amount of water lost
For water to travel at a fast rate across the membrane, it passes through aquaporins
What is tonicity?
Amount of solute in a solution
What does hypertonic mean?
Higher solute concentration than another intracellular solute concentration –> shrink (too little water)
What does hypotonic mean?
Lower solute concentration than another intracellular solute concentration –> swelling (too much water)
What does isotonic mean?
Equal solute concentration on both sides
What are the proteins that conduct active transport called?
They are called pumps, as they force molecules or ions to move from an area of low concentration to high concetration (against conc. gradient)
What is the Na-K pump / NAK ATPase (sodium potassium pump)?
The job is to move sodium ions out of the cell and potassium ions into the cell.
How does the NAK ATPase work?
The pump has a binding site for 3 sodium and 2 potassium ions. The sodium ions come from intracellular, and the potassium ions are extracellular.
AFter 3 Na+ is positioned in the protein, an ATP molecule is split, releasing phosphate which is binded to a location on the exterior of the carrier protein/pump , causing it to change shape from open to intracellular to open to extracellular.
As a result, this releases the 3 Na+ attached to the pump and takes in 2K+ ions before causing the pump to change shape again
Ultimately, 3 Na+ is released, and absorbs 2K+
However, this causes a negative (because amount of ions coming in is not proportional to the amount of ions going out) ELECTRICAL/ELETROCHEMICAL gradient
What is the electrical/electrochemical gradient. Why is it so important?
It is a difference in electrical charge across a space.
This is important as various cellular processes, including the generation of nerve impulses uses the electrical gradient.
This is thus especially important for neurons
In fact, to further boost the negative electircal gradient, channel proteins allow for passive transport of K+ out, further bringing down the electrical gradient
What is facilitated diffusion?
This is where proteins in the membrane assist with facilitating passive diffusion. Some are transport proteins, and acts as channels
Some transport proteins might change shape
These transport proteins assist with diffusion as they help with molecules which might be too big or polar or charged to cross the membrane, and thus need help from a transport protein
The proteins facilitate substances to go through
What is endocytosis?
It is the process of a cell ingesting material by enveloping it in a portion of its cell membrane, and then pinching off that portion of the membrane. Once pinched off, the portion of membrane and its contents become an independent, intracellular vesicle
Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested materials.
extracellular –> intracellular
Example of endocytosis
Phagocytosis is the endocytosis of a large particle. Many immune cells use phagocytes for pathogens
Pinocytosis brings fluid containing dissolved substances into a cell through membrane vesicles
Receptor related endocytosis is endocytosis of a portion of the cell membrane that contains many receptors for a certain substance. Once the surface receptors have bound sufficient amounts of the specific substance, the cell will envelope the cell membrane containing the receptor-ligand complexes
What is exocytosis
It is the process of a cell exporting material using vesicular transport
Many cells manufacture substances that need to be secreted. These substances are packed into membrane bound vesicles within the cell
When the vesicle membrane fuses with cell membrane, the vesicle releases its contents into the interstitial fluid, and the vesicle membrane then becomes part of the cell membrane
(i.e. involves the discharge of vesicle content from intracellular to extracellular space), and results in the incorporation of new proteins and lipids into the cell membrane
intracellular –> extracellular
How do neuron action potentials work?
https://www.khanacademy.org/test-prep/mcat/organ-systems/neuron-membrane-potentials/a/neuron-action-potentials-the-creation-of-a-brain-signal
