Cells. Cell Theory All organisms are composed of one or more cells Cells are the smallest units of...

Cells

Cell Theory

• All organisms are composed of one or more cells

• Cells are the smallest units of life

• All cells come from pre-existing cells

Functions of Life

• Metabolism – all chemical rxn occur in organism

• Growth – grows in any amount

• Reproduction – cells with offspring

• Response – seek survival

• Homeostasis – consistent internal environment, pH and temp

• Nutrition – intake of energy

Order of Size in a Cell

• Organelles* Largest

• Bacteria

• Membrane

• Viruses

• Molecules Smallest

How can we see these things?

• Light Microscope

• Electron Microscope

*Limiting Cell Size

• Surface area – intake of nutrients

• Volume – energy, waste

*Cell Reproduction

• Maintain life

• Pass down genes

• Replace dead cells

• Genes are segments of DNA on a chromosome

Types of Cells

• Bacteria*

• Animal*

• Plant*

*Mitochondria vs. Chloroplasts

• ATP formation

• Double Membrane

• Its own DNA

• Ribosomes

• Mitochondria has crista

• Chloroplast has granum

Stem Cells

• Stem cells are cells that retain the ability to divide and differentiate into various cell types.

*Prokaryotic Cells

• Cell wall

• Plasma membrane

• Flagella

• Pili

• Ribosomes

• Nucleoid

*Eukaryotic Cells

• Larger and more complex than prokaryotic cells

• Endoplasmic reticulum*

• Ribosomes* Lysosomes

• Golgi apparatus*

• Mitochondria

• Nucleus

• Chloroplasts

• Centrosomes

• Vacuoles

*Magnification

• A student observes a cell and draws it, using a high power lens of a light microscope. The diameter of the drawing is 10mm. The actual diameter of the cell is 10μm. What is the magnification of the drawing?

• Magnification=size of image ÷ size of specimen

*Cell Division

• The Cell Cycle

• Mitosis

*The Cell Cycle

• Interphase• G1 phase• S phase• G2 phase

• Mitosis• Prophase• Metaphase• Anaphase• Telophase

• Cell division

• Cytokinesis• Cell division

*Tumour

• Cells that multiply rapidly form a solid mass of cells is called a tumour.

• Damage or error occur within the cell will cause this to happen

Interphase

• Longest phase in the cell cycle• G1, S, G2 G1 is known as “Gap phase one” or “the growth phase one” where cell increases in mass with increase number of organellesS phase is the “Synthesis phase” where main part of replication occurs, replication of chromosomesG2 is known as “Gap phase two” or “growth phase two” where there is an increase in volume and mass in the form of increase of organelles are development of chromosomes and microtubules begin to form for preparation for mitosis

Mitosis

• Mitosis is also known as the “M phase”

• There are four phases in mitosis• Prophase• Metaphase• Anaphase• Telophase Tip: P-Mat is an easy way of memorizing this order

Prophase

• The chromatin fibers become more tightly coiled to form chromosomes

• The nuclear envelope disintegrates and nucloli disappears

• The mitotic spindle begins to form and is complete at the end of prophase

• The centromere of each chromosome has a region called the kinetochore that attaches to the spindle

• The centrosomes move toward opposite poles of the cell due to lengthening microtubules

Metaphase

• The chromosomes are moved to the middle or equator of the cell. Known as the metaphase plate

• The chromosome’s centromeres lie on the plate

• The movement of chromosomes is due to the action of the spindle which is made of microtubules

• The centrosomes are now at the opposite poles

Anaphase

• This is usually the shortest phase of mitosis. It begins when the two sister chromatids of each chromosome are split

• These chromatids, now chromosomes, move toward the opposite poles of the cell

• The chromatid movement is due to shortening of the microtubules of the spindle

• Because the the centromeres are attached to the microtubules, they move towards the poles first

• At the end of this phase , each pole of the cell has a complete, identical set of chromosomes

Telophase

• The chromosomes are at each pole

• A nuclear membrane envelope begins to reform around each set of chromosomes

• The chromosomes smart to enlongate to form chromatin

• Nucleoli reappear

• The spindle apparatus disappears

• The cell is elongated and ready for cytokinesis

*Cytokinesis

• Cytokinesis is not part of mitosis but follows after mitosis

• Animal cells the cell involves an inward pinching of the plasma membrane to form cleavage furrow.

• Plant cells the cell involves a cell plate

• Results are two identical daughter cells that are identical to the parents (contains same number of chromosomes)

*Membranes

• The structure of cell membranes are composed of proteins and lipids(phospholipids)

• The outer cell membrane is called the plasma membrane due to the phospholipid bilayer member

Phospholipids

• Phospholipids are the back bone of the membrane

• Phospholipid structure is compose of glycerol which is a three carbon compound with two of the carbons having a fatty acid tail and third contains an alcohol with a phosphate group attached to it

• Fatty acids are non-polar therefore resists water. Hydrophobic

• The alcohol phosphate group is water tolerant because it is polar. Hydrophilic

Cholesterol

• Only in animal

• Cholesterol is located in the bilayer of the cell membrane, the hydrophobic region, where the fatty acids are located

• These molecules role is membrane fluidity, which changes with temperature

• Fluidity is the rate that objects can past through the membrane, higher the temperature the more easily things can past through

Proteins

• There are two major types of proteins: integral protein and peripheral protein

• Integral protein is hydrophobic and hydrophilic, the hydrophobic region hold the protein in place

• Peripheral protein is only hydrophilic, therefore remains outside the membrane, these proteins are anchored to the member by integral protein

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*Membrane Protein Function

• Hormone binding sites

• Enzymatic action

• Cell adhesion

• Cell-to-cell communication

• Channels for passive transport

• Pumps for active transport

Hormone binding sites

• Proteins that expose their exterior in a particular way to fit perfectly with a hormone(binding) to relate a message to the interior of the cell.

Enzymatic Action

• Cells have enzymes attached to membranes that catalyse many chemical reactions.

• Often relates to the metabolic pathway

Cell Adhesion

• Cell adhesion is provided by proteins when they hook together various ways to make connection.

• Gap Junctions or Tight Junctions

Cell-to-cell Communication

• Includes many molecules of carbohydrates

• Provides an identification label representing cells of different species

Channels for passive transport

• Provides a channel for substances to pass through the membrane from a high concentration to low centration

Pumps for active transport

• Proteins shuttle a substance from one side of the membrane to the another by change shape

• Requires energy

Passive Transport

• Passive transport does not require energy(ATP)

• Passive transport occurs when there is an area of high concentration of a substance moves to an area of low centration.

• The substance moves along what is called the concentration gradient.

• Diffusion and Osmosis are examples of passive transport

Diffusion

• Particles of any type move from a region of high concentration to a region of low concentration

• Examples are oxygen diffusing into the cell while carbon dioxide diffuses out the cell

Osmosis

• Osmosis involves only the passive movement of water molecule across a partially permeable membrane

• A partially permeable membrane is one which only allows certain substances to pass through

• Hyperosmotic concentration is the concentration of high solutes

• Hypo-osmotic concentration is the concentration of low solutes

• Concentration exchange ends when everything reaches equilibrium

Size and Charge

• Substances that are small in size and non-polar move across membranes with ease. Gases like oxygen, carbon dioxide, and nitrogen fit in this category and water glycerol

• Substances that are polar and/or large in size have difficulty passing through the membrane. Examples of these are chloride ions, potassium ions, sodium ions, glusose, and sucrose.

Active Transport

• Requires energy in the form of ATP

• Active transport moves against the concentration gradient

• Facilitated diffusion is an example of active transport

*Facilitated Diffusion

• Facilitated diffusion is a particular type of diffusion involving a membrane with specific carrier proteins that are capable of combining with the substance to aid its movement.

• The carrier protein changes shape to bind to the protein needed for transport.

• Carrier protein requires energy to move against the concentration gradient

Sodium-Potassium Pump

• A specific protein binds to three intracellular sodium ions

• Binding of sodium ions causes phosphorylation by ATP

• The phosphorylation causes the protein to change its shape, thus expelling sodium ions to the exterior

• Two extracellular potassium ions bind to different regions of the protein and this causes the release of the phosphate group

• Loss of the phosphate group restores the protein’s original shape thus causing the release of the potassium ions into the intracellular space

*Endocytosis

• Endocytosis allows macromolecules to cross the cell membrane

• Endocytosis occurs when a portion of the plasma membrane is pinch off to enclose macromolecules or particulates

• The pinching of the membrane changes the shape of the membrane

• The result of this is a formation of a vesicle

*Exocytosis

• Exocytosis usually begins in the ribosomes of the rough ER and progresses through a series of four steps until the produced substance is secreted to the environment outside the cell.• Protein produced by the ribosomes of the rough ER

enters the lumen of the ER• Protein exits the ER and enters the cis side or face of

the Goli apparatus; a vesicle is involved• As the protein moves through the Goli apparatus, it is

modified and exits on the trans face inside the vesicle • The vesicle with the modified protein inside moves to

and fuses with the plasma membrane – this results in the secretion of the contents from the cell