IB BIO Unit 1 - Cell Biology

Outline Cell Theory

1. All living things are made up of cells
2. All living cells come from pre-existing living cells
3. The cell is the most basic unit of life
- There are always exceptions that come with cell theory
- There is debate about how the original cell came to be without spontaneous generation

7 Functions of Life

1. Metabolism
2. Homeostasis
3. Growth
4. Reproduction
5. Response
6. Excretion
7. Nutrition

Outline SA:V ratio rules

The higher the surface area to volume ratio the more efficient a cell is. More surface area means more transportation of nutrients and other substances in and out of the cell. Cells can die when the volume is too much for the surface area because the nutrients and other materials can't move around the cell fast enough.

How are villi, microvilli, alveoli and nephrons similar?

They provide large surface area for molecular exchange.

What does a surface area to volume ratio graph look like - draw it

What is a negative side effect that comes from increased surface area to volume ratio?

Increased surface area can result in an increase of HEAT LOSS

What are the different categories of stem cells?

1. Multipotent - grows up into cells of a closely related family from which it is derived
2. Pluripotent - can grow/differentiate into almost any cell (embryonic)
3. Totipotent - Can grow/differentiate into any type of cell

What are the 2 different types of cells and their "kingdoms"?

Prokaryotic (2)
- Eubacteria
- Archaebacteria

Eukaryotic (4)
- Animalia
- Plantae
- Protista
- Fungi

What is the major difference between Prokaryotic and Eukaryotic cells?

Procaryotic = no membrane bound nucleus
- often unicellular organisms

Eukaryotic = membrane bound nucleus
- often multicellular

What is the prokaryotic cell wall made of?

Peptidoglycan

Draw, Label and annotate a prokaryotic cell?

Nucleoid = region of cytoplasm where the DNA resides
Genophore = circular DNA
Plasmids = autonomous circular DNA molecules that may transfer between bacteria
Slime Capsule = a thick layer used for protection against desiccation (drying out) and phagocytosis
Flagella = tail - long projections containing a motor protein that enables movement
Pilli = hair-like extensions that enable adherence to surfaces (attachment pili) or mediate bacterial conjugation (sex pili)
Cytoplasm
Cell wall - peptidoglycan
Cell membrane

How to most prokaryotic cells replicate?

Binary Fission

Draw, Label and annotate a Animal cell

Draw, Label and annotate a Plant cell

What are the differences between a plant cell and an animal cell?

Plant cells

* Cell wall
* Chloroplasts
* large central vacuole
* fixed shape
* carbs are stored as starch

Animal cells

* no cell wall
* no chloroplasts (often more mitochondria - muscle)
* vacuoles are small and there are multiple
* no fixed shape
* carbs are stored as glycogen

What is a polar molecule?

A molecule in which one end of the molecule is slightly positive, while the other end is slightly negative. Can mean that there is no overall charge.

Outline the structure of a phospholipid

Two distinct regions:
Hydrophilic head with a polar central phosphate group
Hydrophobic tail with two non-polar fatty-acid chains

What is the cell membrane made up of? How does it work?

Phospholipid bilayer

-phospholipids spontaneously arrange to form a bilayer in the
presence of water.

-The water loving heads face outwards to interact with the polar liquid environments (mostly water), while the water fearing (or lipophilic) tails face inwards.

Meaning of Amphipathic?

There are regions of both hydrophobic and hydrophilic areas present

What are the properties of the phospholipid bilayer (cell membrane)?

Semipermeable - restrict the passage of many substances
Fluidity:
- The phospholipids move within the
bilayer
- The fatty acid lipid tails are held
together by weak hydrophobic
interactions

Membrane will continuously break and
reform allowing for some larger
molecules to enter/leave (endocytosis /
exocytosis)

What is endocytosis?

Endocytosis is the process of the cell membrane engulfing materials and entering them into the cell

What are the two types of endocytosis?

Phagocytosis and pinocytosis

What is phagocytosis?

"cell eating"

What is pinocytosis?

"cell drinking"

What is exocytosis ?

The process of excreting materials out of the cell membrane

involves secretor vesicles(transportation membrane bound organelles)

Singer-Nicolson model

= Fluid mosaic model

phospholipid bilayer with membrane proteins and cholesterol imbedded within the phospholipids

Davson-Danielli model

= protein sandwich

phospholipid bilayer covered by membrane protein layer on both the intracellular and extracellular regions

Intracellular

inside the cell

Extracellular

outside the cell

What is the universal solvent?

Water

Hypotonic Solution

Hypoosmotic - more solutes in solution - water coming in

Isotonic Solution

an equal concentration of solutes in one solution compared to another solution

Hypertonic Solution

Hyperosmotic - less solutes in solution - water leaving

Osmolarity

is a measure of solute concentration, as defined by the number of osmoles of a solute per liter of solution (osmol/L)

Semi-permeability

The amphipathic nature of the membranes make it
semi-permeable for SMALL, NON-POLAR molecules to freely pass. - PASSIVE DIFFUSION

Passive diffusion

diffusion that doesn't require ATP - goes along the concentration gradient

goes through amphipathic bilayer

Selectivity

Protein channels may SELECTIVELY allow LARGE, or POLAR molecules to pass depending on the needs of the cell

Active diffusion

diffusion that requires ATP - goes against the concentration gradient

2 kinds of Passive Transport

Simple and facilitated

Simple Diffusion

- no ATP required
- goes along the concentration gradient
- small nonpolar species are able to move freely through the membrane

Facilitated Diffusion

- ATP is NOT required when going against concentration gradient
- larger and or polar species pass through protein channels or
use carrier proteins to pass through the membrane
- If using carrier proteins, active transportation can occur!!(usage of atp)

BIG IDEA - protein channels - CARRIER proteins can go against concentration gradient and use ATP

Proteins in cell membrane

1. integral membrane proteins
- protein channels
- carrier proteins
2. peripheral membrane proteins

Protein channels

- integral lipoproteins which contain a pore via which ions may cross from one side of the membrane to the other

- only select for specific ions

- much faster rate of transport than carrier proteins

- only move molecules along a concentration gradient (i.e. are not used in active transport)

Carrier Proteins

- integral glycoproteins bind a solute and undergo a conformational change to move the solute across the membrane

- only bind a specific molecule via a recognition site

- slower rate of transport than channel proteins

- May also move molecules against concentration gradients in the using ATP (active transport)

Abiogenesis

The theory that the first cells must have arisen from non-living material

Exceptions/problems with current cell theory

- multinucleated cells (striated muscle cells, fungal hyphae and giant algae (some types)

- continuous cytoplasm of some large cells that aren't seperated into smaller cells

- viruses

- 'First' cell without the theory of spontaneous generation

Spontaneous generation

a debunked theory that suggests that the first cell came from spontaneous generation of the correct materials that formed a cell

Endosymbiotic theory

* 2 billion years ago a large bacteria cell 'ate' a bacteria cell
* formed a symbiotic relationship
* bacteria involved in the mitochondria (providing ATP)
reasons:
* bacteria same size as mitochondria
* mitochondria also divide by fission (bacteria cells do)
* mitochondria divide independent of host cell
* mitochondria have own ribosomes
* mitochondria have own DNA (more similar to prokaryotic cells)
* mitochondria have two membranes on exterior - consistent with engulfing process

Louis Pasteur Test

Tests spontaneous generation
- conclusion: bacteria can't spontaneously appear in sterilized nutrient broth

State the phases of the cell cycle

Interphase
1. G1 phase
2. Synthesis phase
3. G2 phase

Mitosis
1. prophase
2. metaphase
3. anaphase
4. telophase

cytokinesis

Interphase is the _________ phase in the cell cycle

longest

G1 phase

- major growth in the cell
- cell is the smallest it will ever be

S phase

- DNA duplicates
- once all chromosomes have been replicated cell enters its second growth phase called G2

Cytoskeletal filaments

network of interlinking protein filaments

- microtubules (major component of cytoskeleton)

help cell with shape, organization of the cell and spindle microtubules/fibers play a major role in cell division

G2 phase

- cell grows and makes preparations for mitosis
- organelles double
- DNA begins to condense from chromatin to chromosomes
- microtubules may begin to form

Histones

DNA proteins

Nucleosomes

A nucleosome consists of a molecule of DNA wrapped around a core of eight histone proteins (an octamer)

Solenoid

coiled string of nucleosomes attached

Looped domains

looped solenoid

Supercoiling

1. DNA wraps around histones forming nucleosomes (groups of 8 histones)
2. Nucleosomes wrapped into solenoid
3. solenoids group together in looped domains
4. final coiling occurs to produce the chromosome

HAPPENS THROUGHOUT G2 and PROPHASE

Centromere

The center component that holds together eukaryotic sister chromatids

after separation the individual chromosomes has its own centromere

Prophase

- nuclear envelope disintegrates and nucleoli disappear
- mitotic spindle completely forms during prophase
- centromere of each chromosome attaches to the spindles
- centroSOMES move towards the opposite poles of the cell as a result of the lengthening microtubules

Metaphase

- chromosomes move to middle of cell (referred to as metaphase plate)
- chromosomes centromeres lie on the plate
- chromosomes movement arise as a result of the action of the spindle
- centreSOMES are ate opposite ends

Anaphase

- typically shortest stage in mitosis
- sister chromatids are split
- chromosomes move to opposite sides of cell
- movement result of shortening microtubules
- each pole has a complete identical set of chromosomes

Telophase

- chromosomes at each pole
- a nuclear membrane begins re-form around each set of chromosomes
- chromosomes start to elongate and form chromatin
- spindles disappear
- the cell is elongated for cytokinesis

Animal Cytokinesis

cleavage furrow forms (contractile ring of microfilaments), pinches and forms two cells

Plant cytokinesis

vesicles align in the middle of the cell, forms cell plate, cell plate attaches to wall of parent cell, new cell wall formed, two cells formed

Phosphorylation

attachment of phosphate group to a molecules or an ion - this transmits signals throughout the cell

side note: common in regulating protein function

\
image relates to cyclin - up next

Cyclins - what are they and what do they do?

Cyclins are a family of regulatory proteins that control the progression of the cell cycle

Cyclins activate *cyclin dependent kinases (CDKs)*, which control cell cycle processes through phosphorylation

* When a cyclin and CDK form a complex, the complex will bind to a target protein and modify it via phosphorylation
* The phosphorylated target protein will trigger some specific event within the cell cycle (e.g. centrosome duplication, etc.)
* After the event has occurred, the cyclin is degraded and the CDK is rendered inactive again

G0 phase?

G0 is a non-growing state that can at times occurs between G1 and S phase

cells will pause between the G1 and S phase due to inactivation of the CDK enzymes - entering the G0 phase

some cells such as nerve and muscle cells, never progress beyond the G0 phase

Chromatin

loose DNA - easily accessible for DNA replication

Chromatid

replicated DNA strands
in pairs - sister chromatids
only referred to during mitosis

Chromosome

DNA supercoiled
can be replicated (1) or replicated (2)

Humans have _____ chromosomes in the cell?

46

Mutagens

can change genetic material of the organism

Carcinogenes

mutagen capable of causing cancer

Oncogenes (2 types)

potential to cause cancer

proto-oncogenes
- promote cell growth and proliferation(cell cycle)

tumor suppressor genes
- repress cell cycle progression and promote apoptosis
- if mutated - deactivate - result in cancer

when healthy oncogenes work together in cell cycle

Metastasis

spread of cancer form one location (primary tumor) to another forming a second tumor

* same cell type as primary - affects the type of treatment required

Benign tumor

tumor may remain in OG location (primary location)

Malignant

tumor that may spread/invade neighboring tissues

Pumps

example: sodium potassium

Why create gradients?

Potential energy = build of usable energy that will erupt = creating larger conc. of energy

What is the role of cholesterol in the cell membrane?

helps with structural integrity of the cell membrane

provides some rigidity to the cell

overall allows the fluidity of the cell without breaking apart

helps with temp changing fluidity of cell