Cells, Tissues, and Systems Vocabulary
Cells, Tissues, and Systems
Unit Overview
Cells
Basic unit of life.
Plant and animal cells are eukaryotic.
Membranes enable specialization.
Tissues
Groups of specialized cells.
Structure determines function (e.g., muscle tissues with many mitochondria).
Systems
Perform specialized functions.
Organs and tissues working together.
Focus on digestive, circulatory, and respiratory systems in animals.
Skill Sets
Working with a micro viewer and microscope.
Memorizing terms and diagrams.
Drawing diagrams (biological, cell, mitosis, etc.).
Major Concepts
Membranes allow for specialization and differentiation of function.
Structure determines function.
DNA contains all genetic information; maintaining DNA integrity is crucial during cell division.
Cells and Cell Division
Cell Theory
All living things are made of one or more cells.
The cell is the simplest unit that can carry out all life processes.
All cells come from other cells.
Cell Types
Eukaryotic
Complex cells with:
a membrane-bound nucleus that houses DNA, along with various organelles such as mitochondria and the endoplasmic reticulum.
Examples:
Plant Cells: Cells that possess a rigid cell wall, chloroplasts for photosynthesis, and large central vacuoles for storage and maintaining turgor pressure.
Animal Cells: Cells that lack a cell wall, contain smaller vacuoles, and usually have more complex lysosomal and Golgi apparatus structures for processing and transporting proteins.
Prokaryotic.
Simple cells that lack a membrane-bound nucleus, typically smaller in size, and possess ribosomes and a single circular DNA molecule.
Organelles
Specific parts within a cell with specific functions.
Nucleus
Contains most of the genetic information (some in mitochondria and chloroplasts).
Contains one or more nucleoli.
Surrounded by the nuclear envelope, a double membrane separating the nucleus from the cytoplasm.
Nuclear Envelope
A double membrane that encloses the nucleus, separating its contents from the cytoplasm.
Nucleolus
Appears as a mass of densely stained granules and fibers.
Protein subunits of ribosomes are made here and then exported to the cytoplasm for assembly.
Ribosomes
Organelles that carry out protein synthesis.
Two types:
Free ribosomes: suspended in the cytoplasm.
Bound ribosomes: attached to the outside of the endoplasmic reticulum or nuclear envelope.
Endoplasmic Reticulum (ER)
An extensive network of membrane-covered channels that transport materials made in the cell.
Connected to the nucleus.
Golgi Apparatus
Flattened sacs (looks like a stack of pita bread) that sort and package proteins and other molecules for transport out of the cell.
Sacs are not interconnected, unlike the ER.
Lysosomes
Consist of digestive enzymes enclosed in a membranous sac.
Help break down ingested substances, releasing nutrients to the cell.
Mitochondria
Organelle with membranes where energy is released from glucose to fuel cell activities.
Chloroplasts
Photosynthesizing organelles which convert light energy to chemical energy (sugars).
Found in plant cells only.
Cell Wall
Tough, rigid structure that surrounds the plant cell’s membrane.
Protects the plant cell and maintains its shape.
Cell Membrane
Separates the inside of the cell from the outside environment.
Controls the flow of materials into and out of the cell.
Cytoplasm
Includes the cytosol (liquid part), organelles, and other life-supporting materials.
Vesicles
Membrane-covered sacs that transport and/or store materials inside the cell.
Help materials cross the cell membrane to enter or leave the cell.
Vacuoles
Contain water and other materials; used to store or transport smaller molecules.
Plant cells have one large vacuole, while animal cells have many small vacuoles.
Cytoskeleton
Helps the cell maintain its structure and provides tracks for vesicles and organelles to move.
Made of filaments and tubules that provide a framework for the cell.
Typical Animal Cell
May include microvilli and flagellum, though not normally present in most cells.
Figures
Figure 2: Typical Plant Cell.
Unique to Plant Cells
Chloroplasts.
Central vacuole and tonoplast.
Cell wall.
Plasmodesmata.
Cell Reproduction
Cell Reproduction: Process in which new cells are formed.
Types of Cell Reproduction:
Asexual Reproduction (Mitosis)
Focus of the course
One parent cell becomes two "daughter" cells
Daughter cells have the exact same genetic information as the parent cell
Occurs in multicellular organisms’ somatic (non-sex) cells
Also occurs in single-cell organisms (e.g., bacteria)
Sexual Reproduction (Meiosis)
Two parents mate to produce offspring
Offspring receive ½ of genes from each parent
Genetic information is a mix of both parents
Occurs in multicellular organisms’ sex cells
Basic Vocabulary
Genome: The whole of the genetic information of an organism
Gene: A heritable factor that controls a specific characteristic
A specific sequence in the DNA (composed of DNA)
Codes for a protein
Chromosome: A thick threadlike, gene-carrying structure found in the nucleus
Condensed version of chromatins
Chromatin: Thin threadlike, gene-carrying structure found in the nucleus
Loose version of chromosome
As a cell prepares to divide, its chromatin coils up, forming compact, distinct chromosomes
Sister Chromatids: Two exact same DNA molecules (formed by DNA replication) that are attached by a centromere
After the two sister chromatids separate during anaphase of cell division, each chromatid is referred to as a chromosome
Cell Cycle of Asexual Reproduction in Multicellular Organism
DNA replication (chromosome forms 2 sister chromatids)
Mitosis (Prophase, Metaphase, Anaphase, Telophase)
Cell division – Cytokinesis occurs
Cell Cycle
Sequence of events from the time a cell is first formed from a dividing parent cell until its own division into two cells.
Consists of:
Interphase
Mitotic Phase
Mitosis
Cytokinesis
Interphase
Accounts for ~90% of cell cycle (NOT a stage of mitosis)
Cell performs its various functions and when many biochemical reactions occur (via transcription and translation)
G1 phase: Cells grow in size
S phase: DNA replication occurs (cell still grows)
G2 phase: Preparation for cell division (cell still grows)
Mitotic Phase
Accounts for ~10% of cell cycle
Consists of:
Mitosis
Nucleus and its contents (i.e., chromosomes) divide and are evenly distributed to two identical nuclei
Unique to eukaryotes
Required for:
Growth of organism
To replace damaged cells
To reproduce asexually
Cytokinesis
Cytoplasm divides in two, creates two new identical cells
Mitosis
Prophase
The chromatin fibers become super coiled, condensing into chromosomes
The duplicated chromosome appears as two identical sister chromatids joined together at the centromere
Spindle begins to form - composed of the centrioles and the microtubules that extend from them.
A pair of centrioles move towards opposite poles
Nuclear membrane begins to disappear
Metaphase
Nuclear membrane has disappeared
Centrioles have moved to opposite poles of the cell
Chromosomes have moved to the equator of the cell
The sister chromatids of every chromosome are attached to the spindle microtubules on opposite poles
The centromeres begin to divide
Anaphase
The centromeres have split
The spindle microtubules pull the 2 sister chromatids of a chromosome apart to form 2 chromosomes
each chromatid is now considered a chromosome
The 2 chromosomes begin moving toward opposite ends of the cell, as their microtubules shorten
By the end of the anaphase, the two ends of the cell have an equivalent number of chromosomes
Telophase
The 2 sets of chromosomes have reached the opposite poles of the cell
A nuclear membrane reappears around each set of chromosomes
Chromosomes uncoil and become less and less visible
Spindle microtubules break down
Cytokinesis
The division of the cytoplasm occurs to make 2 daughter cells
Cleavage furrows form
The cell is pinched in at the cleavage furrows until 2 cells are formed. Animal cells
Plant cells
A cell plate forms at the equator of the cell
A cell wall and cell membranes replace the cell plate
2 cells are formed
Differences in Cell Division between Animal and Plant cells
Plant Cells
No centrioles
A cell plate forms during cytokinesis and is later replaced by cell membranes & cell wall to divide 1 cell into 2
Animal Cells
Centrioles are found at both poles of the cell
Cleavage furrows form at the equator of the cell and cause the cell to be pinched in until 2 cells are formed
Limits of Cell Size, Control and Death
Limitation to Cell Size
Cells are small and cannot grow indefinitely – when they reach a max size, they will stop growing and may then divide
If a cell becomes too large, it becomes problematic because the surface area to volume ratio becomes too small
A large cell would use up materials a lot faster than it would be able to take in materials
Check Points
Vital to normal growth and development
Ensures accuracy
There are 3 main check points
At each checkpoint, there are special proteins that stop the cycle if there are problems
Checkpoints are at the beginning of the G1, S, and G2 phases
The first checkpoint after mitosis is the most important
Cell division will not continue if:
There are not enough nutrients to support cell growth
DNA is damaged
DNA has not replicated
Cell Death
Sometimes cells do not enter the cell cycle and instead, die because they are damaged
When cells die, the contents of the cell leak out and irritate surrounding cells
Cause swelling and redness in that body part
Cell Suicide
Sometimes cells break down in an organized way
Their contents can be used by other cells
Cell suicide is programmed into cells, by “suicide genes”
Cells die and breakdown when the cells are threats to the organism
When DNA is damaged
When cells are infected by a virus
Cancers and Tumours
Cancerous cells are cells that divide uncontrollably
DNA is damaged
Does not leave the cell cycle to die
A clump of cancerous cells is called a tumour
can grow in any organ
can grow to a large size and can spread to other parts of the body and grow uncontrollably there
cancer = diseases caused by the uncontrolled growth of tumours
tumours reduce the effectiveness of other cells and tissues
take up space
use up nutrients needed by normal cells
make extra waste
cancerous cells don’t attach to a surface like normal cells do
this cause cancer to spread
most normal cells undergo 20 to 30 rounds of cell division
after this, programmed suicide occurs to prevent mutation
cancerous cells contain an enzyme called telomerase which causes these cells to continue to divide even when the DNA has mutated
Causes of Cancer
Carcinogens are mutagens that cause cancer
Examples of carcinogens: Asbestos, tobacco smoke, and human papillomavirus (HPV)
Sometimes DNA mutation in cells occurs randomly and checkpoints are missed – causing cells to become cancerous
Chromosomes
Chromosomes exist in pairs
One chromosome from each parent
Every plant and animal has a specific number of chromosomes in the nucleus of every cell
Humans have 46 chromosomes per cell (23 from mom, 23 from dad)
Chickens have 78 chromosomes per cell (39 from hen, 39 from rooster)
Corns have 20 chromosomes per cell (10 from egg, 10 from pollen)
DNA
The structure of DNA was discovered in 1953 by scientists James Watson, Francis Crick, and Rosalind Franklin
Composed of 4 types of building block molecules:
Adenine, Thymine, Cytosine, Guanine
Cell Transport
Solution = solute + solvent
Solute is dissolved in the solvent
Sugar (solute) in water (solvent)
(solute) in blood (solvent)
Solutes are dissolved in water found in the cell
Examples:
Many solutes move in/out of cells
Diffusion = movement of particles from a region of high concentration to a region of low concentration
Over time, particles will spread out evenly
Equilibrium is reached when there is an equal concentration of particles in all areas
Examples of solutes that move in/out of cell via diffusion:
Small lipids
Alcohol
There are 75-100 trillion cells in an adult human body
There are different cells that do different things
Stem cells are unspecialized, undifferentiated cells
Stem Cells
Stem cells are unspecialized animal cells that can produce various specialized cells.
Early in development, human embryos have totipotent stem cells
Can become any kind of cell in the body
As the embryo develops, stem cells become pluripotent stem cells
Capable of producing less types of cells
Later in development and after birth, humans have only adult stem cells
Can produce only specific kinds of cells
Eg: skin stem cells to repair skin, bone stem cells to repair bone
Uses of Stem Cells in Medicine
Stem cells have major medical potentials
Can potentially produce cells that have been damaged
Ex: Bone marrow can produce blood cells in an animal where blood cells have been damaged
Embryonic Stem Cells = cells found in embryos that are less than a week old
Very useful totipotent cells for research
Under lab conditions, can divide for 1 year without differentiating, then potentially differentiate to different types of cells using different chemicals
Ethical problem: taken from in-vitro (from lab) fertilized eggs and using them destroys the embryo
Are embryos “human”?
Researchers have found ways to transform adult stem cells into pluripotent stem cells
Eg: skin stem cells → pluripotent stem cells by using chemicals
Differentiation of Cells
Factors that influence differentiation of cells from stem cells are:
Contents of cell’s cytoplasm
Contents of cytoplasm may differ in each daughter cell after mitosis
Ex: one daughter cell may have a larger vacuole than the other
Environmental conditions
Presence/absence of certain nutrients could cause different cells to develop differently
Other conditions such as temperature could cause differentiation
Ex: Siamese cats: cells that develop at cool temp produce dark hair → tips of cats feet, tail ears, and nose are cooler, these parts have darker hair
Influence of neighboring cells
Substances produced by neighboring cells could diffuse to the cells and influence differentiation
Similar cell conditions form similar cells
Cells that experience similar conditions become specialized to do similar jobs
Tissues are formed from similarly specialized cells
Contaminants can cause abnormal development
Chemical and radiation contaminants can cause abnormal differentiation
Ex: 1 legged frogs
Plant Cells
Plants also have stem cells - called meristematic cells
Meristematic cells are active throughout the life of a plant
Found in:
tips of roots
stems
in a layer in the stem called cambium
Cell Specialization and Tissues
All cells contain the basic characteristics required for life, and as such, contain the typical parts of the cell, however, to efficiently accomplish certain bodily functions, cells will specialize.
Specialized cells have physical and chemical differences that allow them to perform very specific tasks.
How then do cells specialize/differentiate?
Differentiation of Cells
Factors that influence differentiation of cells from stem cells are:
Contents of cell’s cytoplasm
Contents of cytoplasm may differ in each daughter cell after mitosis
Ex: one daughter cell may have a larger vacuole than the other
Environmental conditions
Presence/absence of certain nutrients could cause different cells to develop differently
Other conditions such as temperature could cause differentiation
Ex: Siamese cats: cells that develop at cool temp produce dark hair → tips of cats feet, tail ears, and nose are cooler, these parts have darker hair
Influence of neighboring cells
Substances produced by neighboring cells could diffuse to the cells and influence differentiation
Similar cell conditions form similar cells
Cells that experience similar conditions become specialized to do similar jobs
Tissues are formed from similarly specialized cells
Contaminants can cause abnormal development
Chemical and radiation contaminants can cause abnormal differentiation
Ex: 1 legged frogs
Tissues
Groups of cells (specialized) that function together to perform specialized tasks.
There are 4 main tissues in all animals:
Epithelial, muscle, nerve, connective
Plant Tissues
There are 4 types of tissues in plants:
epidermal tissue
vascular tissue
ground tissue
meristematic tissue
Meristematic Tissue
unspecialized tissue that is able to divide by mitosis
found in several locations of the plant
responsible for growing new parts of the plant
Epidermal Tissue
forms the protective outer covering of the plant
the epidermal tissue on top and underside of the leaf is clear and thin
allows the exchange of materials and gases into and out of the plant
stomata – specialized guard cells that form a tiny opening is where this happens
allows , water vapor, and to move into or out of the leaf
most stomata are found on the underside of the leaf
Ground Tissue
most of the plant is made from ground tissue
function depends on where it is found in the plant
in stem: provides strength and support
in roots: stores food and water
in leaves: where photosynthesis occurs
Photosynthesis: literally translated into “making food from light.” The process whereby plants absorb light energy, as well as and water, and produce oxygen and sugars (basic food building blocks): (ground tissue in stems)
Vascular Tissue
two types:
Xylem – responsible for the movement of water and minerals from roots up the stem to the leaves where they are used for photosynthesis
Phloem – transports sugar produced during photosynthesis from leaves to other parts of the plant where it is used to provide energy
Organs and Organ Systems
An organ is an organized group of two or more tissue types that performs a specific function (i.e.: heart, brain, lungs, etc.).
Generally, but not always, organs function within a single organ system only.
An organ system consists of one or more organs and other structures that work together to perform specific bodily function(s) (i.e.: cardiovascular, nervous, respiratory, etc.).
There are dozens of different organs within the human body; the focus will be on the systems and the roles particular organs play in these systems.
There are 11 organ systems that work together in the human body:
Circulatory System – transports blood, nutrients, gases, and wastes throughout the body
Digestive System – takes in and breaks down food, absorbs nutrients and removes solid waste from the body
Respiratory System – exchanges gases in lungs
Excretory System – removes liquid waste from the body
Immune System – protects and defends the body against infections
Muscular System – works with bones to move parts of body
Endocrine System – makes and releases hormones to keep various body systems in balance
Reproductive System – involved in producing offspring
Integumentary System – creates a waterproof barrier around the body, includes skin, hair, nails
Nervous System – detects changes in the environment and signals changes to the body which then responds
Skeletal System – supports and works with muscles to move parts of the body
The focus of this course will be on the digestive, circulatory, and respiratory systems.
Digestive System
Pathway of food:
In mouth – mechanical breakdown by teeth, then by chemical breakdown by enzyme amylase in saliva
Food is swallowed through the pharynx
Passes into muscular tube called the esophagus
Walls of the esophagus contract and relax, pushing small chunks of food into the stomach
Food enters stomach
Epithelial tissue in the stomach secretes gastric juices that continue to chemically break down the food
Enzyme pepsin is found in the gastric juice; it breaks down proteins
Hydrochloric acid is also found in the gastric juice.
provides an acidic environment for pepsin to work properly
Stomach lining also secretes mucus, which protects the stomach wall from breaking down because of the gastric juices
Churning of stomach muscles mechanically breaks down food further
After digestion in the stomach, food is in liquid form.
Liquid form of food enters the sphincter, a round muscle at the bottom of the stomach
The sphincter contracts and relaxes, moving food into the small intestine.
Small intestine further digests food, then absorbs nutrients from the fully digested food.
The first meter of the small intestine is called the duodenum – this is where most digestion of food takes place
Organs such as the pancreas, liver, and gallbladder release more digestive enzymes into the duodenum to chemically digest the food
When the digested food moves into the remaining parts of the small intestine, interior folds called villi and microvilli absorb the nutrients and water into the bloodstream
The villi and microvilli increase surface area to maximize nutrient and water absorption
Remaining food moves into the large intestine
Large intestine includes colon, rectum, anus
The large intestine is shorter but has a larger diameter than the small intestine
The large intestine contains bacteria (i.e.: E. coli) that helps with final digestion and producing essential vitamins such as vitamin K
Water, vitamins, and various salts from the digested food are absorbed by the large intestine into the bloodstream
Waste and undigested food are removed through the anus as feces
Circulatory System
Key words
Pulmonary: lungs
Atria: upper chambers
Ventricles: lower chambers
Veins & vena cava: vessels that bring blood to the heart
Arteries & Aorta: vessels that bring blood out of the heart
The walls of the left ventricle are thicker than those of the right ventricle
Need thick powerful muscles in the left ventricle to pump blood to the body
Aorta = largest blood vessel
Need a large size to pump oxygen-rich blood to the body
Path of Blood
Blood is collected in the atria via veins
Atria walls contract, blood is pumped from the atria to the ventricles via opened atrio-ventricular valves
Semi-lunar valves are closed to prevent blood from flowing to arteries while the ventricle fills up with blood
Ventricle walls contract, causing a rise in blood pressure
High blood pressure causes atrio-ventricular valves to close to prevent backflow of blood to atria
High blood pressure also causes semi-lunar valves to open to allow blood to be pumped from ventricles to arteries
As blood leaves ventricles, pressure inside the ventricles drops and ventricles stop contracting
The semi-lunar valves close to prevent backflow of blood from arteries to ventricles
Types of Blood Vessels
Artery
Wall: thick, able to withstand high blood pressure
Vein
Wall: thin, able to be pressed flat by adjacent muscles to help move blood along
Capillary
Wall consists of one layer of adjoining epithelial cells
Capillary beds = areas where branches of capillaries are close to one another
Capillaries bring blood into close contact with tissues to bring in and nutrients and to remove and wastes from the tissues
Respiratory System
Function of the respiratory system: obtain oxygen and release carbon dioxide
Air Pathway
Air enters through the nostrils (air is filtered by nose hair)
↓ nasal cavity (air is warmed, humidified, and sampled for odors)
↓ pharynx
↓ larynx
↓ trachea (aka windpipe)
↓ bronchi (there are 2, each leads to 1 lung)
↓ bronchioles
↓ alveoli (clusters of air sacs with very large surface area, surrounded by capillaries)
Ventilation Mechanism
Inhaling
External intercostals muscles contract, cause ribcage to move up and out
Diaphragm contracts, causing it to become flat and move down
Causes an increase in the volume of the thorax
Pressure inside the thorax drops below atmospheric pressure
Air flows into the lungs (down air pressure gradient from outside the body) until pressure inside = atmospheric pressure
Exhaling
Internal intercostals muscles contract, causing ribcage to move down and in
Abdominal muscles contract, pushing the diaphragm up
Causes a decrease in the volume of the thorax
Pressure inside the thorax rises above atmospheric pressure
Air flows out of lungs until pressure inside = atmospheric pressure
Elastic recoil of lungs helps exhalation
Alveolus for Gas Exchange
Gas exchange occurs in alveoli of lungs
Alveoli are very small
Many (millions of) alveoli provide a large total surface area
A thin, single layer of flattened cells on the wall of each alveolus decreases the distance that gases need to diffuse across
A moist lining on the alveolus wall allows gases to be dissolved in the water
A dense network of capillaries (tiny blood vessels) surrounds the alveolus to remove brought in from the rest of the body and to transport to the rest of the body.
Hemoglobin, the protein found in red blood cells, picks up from the alveoli to transport to the rest of the body
Plant Organs
There are 4 organs in plants
Roots
Leaves
Stem
Flower or fruit
Roots
Anchor plant in soil
Collect water from surrounding and transport it to the stem and store food made in other parts of the plant
The center of the root is made up of ground tissue and vascular tissue
The bottom of the root is covered with protective epidermal tissue known as the root cap
Below the epidermal tissue is the meristematic tissue
Leaf
Tissues in leaf work together to perform photosynthesis
Vascular tissue carries water for photosynthesis from root up the stem to the leaf
Vascular tissue carries sugar produced to the rest of the plant
, and excess water exit through openings in leaf epidermal tissue (stomata)
These openings are controlled by guard cells
Most of the leaf is made up of specialized ground tissue called mesophyll where photosynthesis takes place
Stem
Performs 2 major functions:
Transports water and nutrients throughout plant
Supports leaves and flowers
Epidermal tissue provides a protective covering and allows the exchange of gases and water
Also secretes a waxy substance known as the cuticle that forms a protective coating and reduces water loss
Ground tissue provides the stem with strength and support
Vascular tissue transports substances around the plant
Flower
The reproductive structure of the plant
The main function is to produce seeds through sexual reproduction
Contains:
Male organs: stamens
Each stamen consists of a filament with an anther at the tip
Anther produces male sex cells called pollen
Female organs: pistil
Consists of the ovary, style, and stigma
Female sex cells are called eggs, located in the ovary
When the pollen and egg unite, the fertilized egg becomes a seed
In some plants, seeds are surrounded by flesh and are called fruit, and in other plants, seeds have no fleshy covering but are encased in a hard shell
Plant Organ Systems
Has 2 organ systems:
Shoot system
Everything above ground
Stem, leaves, buds, flowers, fruits
Root system
Everything underground and aerial roots (above-ground roots)
Transpiration
Transpiration is the evaporation of water through the stomata in the leaves,
allows water to move from roots to the leaves
How it Works
As each water molecule evaporates, it creates a transpiration pull on the adjacent water molecules, which pulls the water up the xylem to the leaves
Once the water reaches the leaf, the water is moved from the xylem into the ground tissue
The leaves lose a lot of water because of evaporation through the stomata
This evaporation allows transpiration pull and water is continuously drawn up the stem