IB Biology Topic 1

Cell Theory

1. All living things are composed of cells
2.The Cell in the fundamental unit of life
3. Cells only arise from pre-existing cells

Striated Muscle

Long Cells, (300 mm), multiple nuclei, questions cell theory

Acetate Fungal Hyphae

challenges idea that cell is a single unit, multi-nucleated, and continuous cytoplasm. Cell walls composed of Chitin

giant algae

challenges that notion that cells must be small, and simple in structure. Size of 5-100mm and complex in form.

response

Living things can respond to and interact with the environment

Homeostasis

The maintenance and regulation of internal cell conditions, e.g. water and pH

Growth

Living things can grow/change

excretion

removal of metabolic waste

reproduction

living things produce offspring, sexually or asexually

nutrition

feeding by either the synthesis of organic molecules (e.g. photosynthesis) or the absorption of organic matter

SA to Volume Ratio

A larger SA:Vol ratio can mean that a cell can act more efficiently. For every unit of volume that requires nutrients or produces waste. There is more membrane to serve it

How to maximize SA to Vol ratio?

Cells divide, They use membranes to carry out processes, organs will fold up to maximize the ratio

Rate of Metabolism

a function of mass/volume

emergent properties

when things are added more properties arise

specialized cells

All specialized cell and the organs constructed are from differentiation

Stem Cells

unspecialized cells that can differentiate into many cell types - Embryonic - Cord Blood - Adult (bone marrow)

Totipotent

Can differentiate into any cell

pluripotent

Can differentiate into many cells

multipotent

can differentiate into a few closely related cells

unipotent

Can regenerate,but only into associated cell type

Stagardt's Macular Distrophy

A recessive condition for the eyes, stem cells are treated to become retinal cells. Cells attach to the retina and improves central vision

Lukemia

Hematopoietic Stem Cells (HSCs) are harvested from bone marrow, peripheral blood or umbilical cord blood
Chemotherapy and radiotherapy used to destroy the diseased white blood cells New white blood cells need to be replaced with healthy cells. HSCs are transplanted back into the bone marrow HSCs differentiate to form new healthy white blood cells

Embryonic Stem Cell Structure

Prokaryote Cell Structure

approximately 0.5 μm

Prokaryotic Reproduction

Asexually through binary fission.

Steps of Binary Fission

1. Two loops attach to membrane
2. Elongation and pinches off
3. Two identical cells

Properties of Prokaryotes

Their DNA is not enclosed in within a membrane and forms on circular Chromosome
Their DNA is free; it is not attached to proteins
They lack membrane-bound organelles. Ribosomes are complex structures within the plasma membrane, but they have no exterior membrane
Their cell wall is made up of a compound called peptidoglycan
They usually divide by binary fission, a simple form of cell division
They are characteristically small in size, usually between 1 and 10 µm

Eukaryote Cell Structure

1 micrometer

Nucleus

Generally Spherical with a double membrane. Pores and holes are present. Contains Chromosomes.

Mitochondion

Has a smooth outer membrane. Folds are cristae. Variable Shape. Site of ATP production by aerobic energy

Free Ribosomes

80S ribosomes. No membrane, appear as dark granules in cytoplasm. Synthesizes proteins to function in cytoplasm.

Rough Endoplasmic Reticulum

Consists of Flattened membrane sacs (cisternae). Located near nucleus. 80S ribosomes are attached to outside of cisternae
rEr synthesizes transported proteins by vesicles to golgi for modification

Golgi Apparatus

Contains cisternae
No attached ribosomes
often sited close to plasma membrane
shorter and more curved than the rER. modifies proteins from the rER , the repackaged in vesicles

Vesicles

A single membrane with fluid
Small
Transport Materials inside cell

Lyosomes

Spherical with single membrane
Golgi vesicles
Digestive enzymes from breakdown of:
food
unwanted organelles
cell itself
High concentration of enzymes, cause this to stain heavily and hence appear dark on micrographs

Vacuoles

Single Membrane with fluid inside
Plant cells vacuoles are large and permanent often occupying cell volume
In animals vacuoles are smaller and used for various other reasons

Flagellum

Thin projection from cell surface. Contain microtubules
Used to move cell

Cillia

Thin projections from cell surface
Contain Microtubules
Used to either move cell or the move the fluids next to the cell

Microtubules

Small Cylindrical fibers
Have a variety of functions, part of flagella. Cell division

Centrioles

Nine triple miroctubules
manly found in animal cells not vascular plants of fungi

Chloroplast(plant only)

Many, but not all plant cells contain chloroplasts
Inside are thylakoids
Flattened membrane
Shape is variable,but usually ovoid
Site of photosynthesis and hence where glucose is produced
Starch grains may be present if photosynthesis is quick

Cell Wall (plants only)

extracellular secreted by plants
permeable
Strong
Hard to Digest

Ribosomes in Prokaryotic

70S

Ultrastructure

is all the structures of a biological specimen that are at least 0.1nm in their smallest dimension

Phospholipid Structure (Words)

Hydrophillic Head
Hydrophobic Tail

Emergent Property of Phospholipid

Heads are wet and tails are dry

Phospholipid Bilayer

is one way that the tails are removed from water

Plasma Membrane Structure

Integral Proteins

Permanently embedded many go all the way through and are polytopic, some are monotopic

Polytopic

Many Surfaces

Peripheral Proteins

Temporary association and are monotopic

oligosaccharide

sugar chain attached. Cell recognition by immune system as hormone receptors

T in Tracie

Transport

R in Tracie

Receptors

A in Tracie

Anchorage

C in Tracie

Cell Recognition

I in Tracie

Intercellular Joinings

E in Tracie

Enzymatic Activity

Transportation

Protein Channels and Pumps

Receptors

Peptide based hormones

Anchorage

Cytoskeleton attachments and extracellular matrix

cell recognition

MHC proteins and antigens

Intercellular joinings

Tight Junctions and plasmodesmata

Enzymatic Activity

Metabolic pathways

Cholestrol

Makes phospholipids pack more tightly and regulates fluidity and flexibility of memebrane.

What does presence of cholesterol do?

restricts movement. Disrupts regular packing of the hydrocarbon tails. This increases flexibility

Signer- Nicolson

Membrane proteins are varied in size and globular. Such proteins are unable to form continuous layers

Davson-Danielli

A protein-lipid sandwich. Proteins coat surface. Do not permeate the bylayer.

Falsification

The fracture occurs along lines of weakness, including the center of membranes.
The fracture reveals an irregular rough surface inside the phospholipid bilayer

Selectively Permeable

Some cannot pass through and different forces

Diffusion

Net movement of particles from high to low concetration.

Osmosis

When a cell is submurged water molecules pass through the cell from low to high solute concentration.

Hypertonic

Higher concentration of solutes

Isotonic

When the concentrations are equal on both sides

Hypotonic

lower concentration of solutes

Facilitated Diffusion

proteins recognize a particular molecule and help it move across the membrane.