Topic 2 - Cells

Amoeba, Chlorella, Euglena

• 1. living organisms are composed of cells
• 2. cells are the smallest units of life
• 3. cells come from pre-existing cells

• 1. Metabolism - chemical reactions inside the cell
• 2. Response - react to stimuli
• 3. Homeostasis - control conditions inside cell
• 4. Growth - increase in size
• 5. Reproduction - produce offspring
• 6. Nutrition - obtain food

1nm

10nm

100nm

1um

less than 10um

<100 um

Magnification =

measured length of the image /measured length of the specimen

• As the organism gets bigger its surface area to volume ratio decreases. This then is a factor limiting cell size.
• As the cell gets bigger the ratio decreases. If the ratio decreases the rate of exchange decreases.

A cell that has the capacity to divide and has the ability to differentiate along different pathways.

Using cord blood for

Grab a pencil and draw the diagram quickly and label the same.

• Plant cell wall maintains shape, prevents excessive water uptake and holds plant up
• Animal cells secrete glycoproteins which functinos in support, adhesion and movement

Forms a protective outer layer to prevent damage from outside and stops bursting if internal pressure is too high

Controls entry/exit of substances - pumping some of them in by active transport

Contains enzymes to catalyse chemical reactions of metabolism and contains DNA in region called nucleoid

Hair like structures projecting from cell wall. Can be used to pull two bacterial cells together.

Solid protein structures, projecting from cell wall which rotate and cause locomotion

Make proteins by translating mRNA

Region of cytoplasm that contains naked DNA - the genetic information in the cell

By binary fission (asexual reproduction) daughter cells have identical genetic information as parent cell

• MV - microvilli - increased surface area for uptake of substances
• M - mitochondria - for release of energy
• L - lysosomes - clean up junk in cell
• rER - rough endoplasmic reticulum - transports proteins
• PM - plasma membrane - controls what goes in/out cell
• GA - golgi apparatus - modifies proteins

• 1. Cell wall - only in plant cells, not in animal cells
• 2. Chloroplasts - only in plant cells, not in animal cells
• 3. Polysaccharides - starch used as storage compound in plant cells and glycogen is storage compound in animal cells
• 4. Vacuole - large and fluid filled in plant cells, not usually present in animal cells
• 5. Shape - fixed shaped in plant cells - usually regular. Able to change shape in animal cells - usually rounded

• G1 The cell performs its normal differentiated function. Protein synthesis/ mitochondria replication/ chloroplast replication.
• S DNA replication. At this point the mass of DNA in the cell has doubled.
• G2 Preparation for cell division

• Prokaryotes are less than 5um, eukaryotes are more than 10um
• Prokaryotes are always unicellular, eukaryotes are often multi-cellular
• Prokaryotes have no nucleus but have a naked loop of DNA (nucleoid) eukaryotes have a membrane bound nucleus with linear chromosomes bound with histones
• Prokaryotes have no membrane bound organelles eukaryotes have membrane bound organelles
• Prokaryotes have small ribosomes (70S) eukaryotes have large ribosomes (80S)
• Prokaryotes have no mitochondria eukaryotes have mitochondria
• Prokaryotes have cell division by binary fission eukaryotes have cell division by mitosis/meiosis
• Prokaryotes' reproduction is mainly asexual, eukaryotes' reproduction is asexual or sexual

When cells become different cell types to perform different jobs.

• Hormone binding sites
• Immobilized enzymes
• Cell adhesion
• Cell-to-cell communication
• Channels for passive transport
• Pumps for active transport.

Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration.

Osmosis is the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.

They are the result of uncontrolled cell division and that these can occur in any organ ortissue.

Is an active period in the life of a cell. Many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts.

• Growth
• Embryonic development
• Tissue repair
• Asexual reproduction

Passive net movement of molecules from regions of high concentration to low concentration, through a selectively permeable membrane, facilitated by carrier proteins.

A group of similar cells all performing the same function.

• Pink balls = hydroPHILIC phophate heads
• Sticks = hydroPHOBIC lipid tails

Peptidoglycan

Passive transport involves no expenditure of energy on the part of the cell and includes diffusion, facilitated diffusion and osmosis.

Active transport requires the expenditure of energy and it includes the sodium–potassium pump, endocytosis, and exocytosis.

The sodium–potassium pump is extremely important in the human body because it brings about the proper ion levels within nerves and muscles so that they can operate efficiently.

Endocytosis occurs when a portion of the plasma membrane is pinched off to enclose macromolecules or particulates needed by the cell. This results in the formation of a vesicle inside the cell.

Exocytosis is essentially the opposite of endocytosis. The Golgi apparatus is essential to the process of exocytosis.

Cytokinesis in plant cells occurs with the formation of a cell plate inside the cell and spreading out. Cytokinesis in animal cells occurs with the pinching in of the plasma membrane resulting in a cleavage furrow. It is the presence of the cell wall in plant cells but not in animal cells that brings about this difference in cytokinesis.

Restoration of insulation tissue in neurons (from May 2012 paper)

10nm

• Polar amino acids
• HELP: Polar bears (live on the 'edge' of the planet ...therefore, polar amino acids like to be on the edge of membranes - either sticking out from cell membranes - or forming channels.

• The are the parts of the proteins that cause them to get embedded into the membrane
• HELP: Polar bears live on the 'edge' of the planet. Non polar bears.....opposite (inside)
• It's silly, but might help you remember!