Biology Pre-IB Term 1 / Summary 1.1 - 1.3

The Cell Theory

1. All living things are composed of cells

2. Cells are the smallest units of life

3. All cells come from pre-existing cells

What do all cells contain?

cytoplasm, a plasma membrane, genetic material, cell activities through chemical reactions and their own energy release system

What are the relative size of cells?

In order: Molecules, membranes, viruses, bacteria, organelles, eukaryotes

1nm, 10 nm, 100 nm, 1 um, 10 um, 10 - 100 um

Atypical Examples of Cell Theory

Red blood cells (no nucleus), Phloem sieve tube elements (no nucleus), Aseptate fungal hyphae (multinicleate in a filamentous structure), skeletal muscle cells (multinucleate).

The Functions of Life

•Metabolism: chemical reactions inside the cell, e.g. cell respiration to release E.

•Response: react to stimuli.

•Homeostasis: keep conditions inside the organisms within set limits.

•Growth: irreversible increase in size.

•Reproduction: produce offspring sexually or asexually.

•Excretion: getting rid of waste products of metabolism.

•Nutrition: obtaining food needed for E and growth.

Unicellular vs. Multicellular

Uni- 1 cell, responsible for ALL functions of life. e.g bacteria, paramecium

Multi- 2+ cells, differentiated to make different tissues to perform specialised functions

Prokaryotes

lack membrane-bound organelles (structures that perform a specific function)

What cell parts are in a Prokaryote?

Flagellum

Ribosomes

Pilli

Cell Wall

Cytoplasm

Nucleoid

Plasma Membrane

Eukaryotic cell

membrane-bound organelles

multicellular

Compare Eukaryote and Prokaryote cells

Prokaryote-

'smaller-10microns

'cell wall

'naked DNA (no protein)

'DNA free in cytoplasm

'Circular/closed loop DNA/chromosones

'some have plasmids

'1 chromosone

'no introns or extrons

'70S ribosomes

'no membrane bound organelles

'no mitochondria

Eukaryote-

'Larger, 100microns

'DNA w/ proteins/histones

'DNA in membrane bound nucleus

'Linear chromosones

'no plasmids

'multiple chromosones

'introns + extrons

'80S ribosomes

'membrane bound organelles

Compare a plant and animal cell

Plant:

Cell wall - made of cellulose for strength and support of the cell.

Chloroplasts - surrounded by two membranes and allow photosynthesis

Large vacuole - storage organelle

Store carbohydrates as starch.

Do not contain centrioles

Fixed, angular shape

No cholesterol in the cell membrane

Animal Cell:

No cell wall

No chloroplasts

Small vacuole

Store carbohydrates as glycogen

Contain centrioles

Flexible, round shape

Have cholesterol in the cell membrane

Identify the functions of life on a prokaryote cell

Excretion-plasma membrane

Reproduction - nucleus

Response- cillia

Metabolism- cytoplasm

Nutrition- vacuoles

Growth- Assimilation

Homeostasis - contractile vacuoldx

Light Microscope

enables examination of small objects not visible to the naked eye. It uses light rays and lenses to enlarge images. It has low resolution. Specimens may be alive or dead. They are relatively cheap.

Electron Microscope

uses electron beams to capture an image and enlarge it. Allows for high resolution 3D images. Much greater magnification power than a light microscope. Only dried and dead organisms are seen. Expensive.

Magnification

The size of an enlarged image

Resolution

The clarity of an image

The features of a microscope

Eyepiece

Coarse adjustment knob

Fine adjustment knob

High and low power objective lenses

Stage

Light

Magnification Formula

Magnification = measured length / scale bar label

Actual Size Formula

actual size = measured length / magnification

Measured Length Formula

Measured length formula = image size / magnification

Stem Cells

undifferentiated cells by expressing genes and not others

Can be used to treat leukemia, lymphoma and diabetes, and repair tissue/heal wounds

They are capable of differentiating into various cell types.

Plant stem cells are found in meristems

Animal stem cells are found in embryos, umbilical cord cells, and some adult cells (e.g. bone marrow)

Phospholipid Bilayer

Plasma membrane layers composed of phospholipid molecules arranged with polar heads facing the outside and nonpolar tails facing the inside.

Phosphate hydrophilic head

Fatty acid hydrocarbon lipid tails

Hydrophobic fatty acid tails

Saturated Fatty acids- straight chains - packing to form bilayers - reduces fluidity and permeability - however stronger and high melting point - thicker and high density

Unsaturated fatty acids - one or more kinks so packs together loosely - flexible - lower melting points

Ideal ratio of these depends on the temperature the cell experiences

The Fluid Mosaic Model

model that describes the arrangement and movement of the molecules that make up a cell membrane

highlights the structure of the membrane is flexibile, adaptable, and in motion

Integral proteins

permamently embedded inside the membrane.

Enzymes - sites for chemical reactions

Pumps - for active transport of molecules

if the integral protein goes all the way through the membrane, it is 'polytopic'

one surface penetrating is monotopic

Peripheral proteins

temporarily attatched/embedded to the outer layer of the membrane. Acts as receptors and 'recognises' other cells.

Monotopic

Cholesterol

makes the phospholipids pack more tightly and regulates the fluidity and flexibility of the membrane. It stabilises membranes at higher temperatures and preventing stiffening at lower temperatures.

Glycolipids and Glycoproteins

1 is carbohydrates (monodaccharide) linked to lipids (1 or 2 hydrocarbon chains) that fit into the hydrophobic core of a membrane

2 is conjugated proteins with carbohydrate as the non polypeptide component.

Protein part is embedded in the membrane. Carbohydrate part projecting out the exterior environment of the cell.

ROLE: cell to cell communication and cell recognition, and can allow adjacent cells to bind together forming a tissue.

Draw the fluid mosaic model of a membrane

It should contain:

-ion channel protein (with pore)

-peripheral protein

-cholesterol

-integral protein (polytopic)

-phospholipid bilayer

-glycoprotein and glycolipid

The methods of moving particles across membranes

1.Simple diffusion (PT)

2.Facilitated diffusion (PT)

3.Osmosis (PT)

4.Active transport (AT)

5.Endocytosis and exocytosis (AT)

Three solutions

1.Diluted solution (little solute, can dissolve more solute)

2.Concentrated solution (lot of solute, can dissolve little more)

3. Saturated solution (max solute, cannot dissolve any more, excess solute at the bottom)

{usually dissolved in an aqueous solution)

Diffusion

The passive net movement of molecules from regions of high concentration to low concentration

(higher concentration gradient = increased diffusion rate as molecules have more energy)

Osmosis

-The passive net movement of water molecules from regions of low solute concentration to high solute concentration, through a partially/selectively permeable membrane

-movement down a concentration gradient (but specifically the water molecules)

Facilitated Diffusion

The passive movement of specific molecules across cell membranes, faciliated by carrier proteins through a selectively permeable membrane (down the concentration gradient)

Comparison of diffusion and osmosis

Similarities - passive and down a concentration gradient

Differences - Diffusion is of solutes + membrane not needed

Osmosis considers water molecules only + partially/permeable membrane essential

Importance of osmotic control

to prevent damage to cells and tissues

hypertonic

osmosis- more water outside the cell

animal - shrivelled (crenated) - plasma membrane that develops indentations due to being bathed in a hypertonic solution

plant - plasmolysed - cell is flaccid/floppy - plasma membrane pulls away from cell wall

dehydration

isotonic

normal water balance inside and outside the cell (osmosis)

hypotonic

more water inside the cell than outside

animal - lysed (the cell membrane pops)

plant - turgid

turgor pressure - high pressure inside cell due to water entering (osmosis). This provides support and strength to a plant

Water potential

Measure of potential energy of water per unit of volume of water, relative to the potential energy of pure water at standard conditions.

In a hypertonic solution (lots of particles dissolved):

*osmolarity high

*water potential low

*solute concentration high

In a hypotonic solution (few particles dissolved):

*osmolarity low

*water potential high

*solute concentration low

passive transport

does not require energy. Down a concrentration gradient (high to low)

active transport

requires energy in the form of ATP. Against a concentration gradient using membrane protein pumps. Key for homeostasis in organisms.

Transmembrane (polytopic) proteins

recognises a particular molecule (thats large and polar and cant get across via diffusion) and helps it move across the membrane. The direction it moves is dependent on the concentration gradient.

Potassium channels

Voltage gated. Enable the facilitated diffusion of potassium out of the axon.

Sodium potassium pumps

active transport mechanisms that pump Na+ ions out of neurons and K+ ions in

ATP (adenosine triphosphate)

The wonder molecule. Used to power most cellular processes, such as active transport and DNA replication.

Exocytosis

the export of macromolecules from the cell. ATP is required. Active transport.

Endocytosis

The import of macromolecules (enter cell process).

ATP is required to make a vesicle this way.

Phagocytosis

the ingestion of solid molecules (when referring to endocytosis)

Pinocytosis

The ingestion of liquids and solutes (when referring to endocytosis)

Draw a diagram of endo and exo cytosis :)

Lable the vesicle forming/leaving.