Unit 1 - Cells

The cell theory?

• All cells come from pre-exisitng cells

• Cells are the smallest unit of life

• All living are made fo cells

Resolution?

The ability of a microsocpe to distingush details of a sepcimen

Magnification?

The ratio of an objects image size to its actual size

Compare light and electron microsocopes?

• Specimen - Light = Living cells or dead , Electron = Dead

• Size - Light = smaller, Electron = Large

• Cost - Light - Cheaper, Electron = Expensive

• Resolution - Light = Less, Electron = Higher

• Colour - Light = Color image, Electron = Black and white

Why are fluroscent stains beneficall

They help visualises specific cellular components

Outline immunofluroesecence technology?

Antibodies that bind to target antigens in cells that are linked to fluorescent light and emit visible light under UV of specific wavelengths

Cryogenic electron microscopy?

A type of electron microsocopy that rapidly freezes samples preserving their structure

Outline cryogenic electron microscopy?

• The sample is flash frozen in its natural state

• Placed in electron microscope

• Electron beam passes through sample

Outline freeze fracture electron micrososcopy?

• Cells are rapidly frozen

• The frozen sample is fractured along the membrane

• The internal surface of the membrane is cracked and exposed

• Replica is viewed under electron microscopy

Function of a cell wall?

Provides structure support and protection

Function of plasma membrane?

Regulate substance transport

Function of cytoplasm?

Site of metabolic reaction

Function of ribosome?

Site of protein synthesis

Function of chloroplast?

Converting light energy to chemical energy

Function of Nuceloid/nucleus?

Managing genetic material

Function of mitcohondira?

Producing ATP through cellular respiration

Compare and contrast prokaryotic and eukaryotic cell structures?

• Nucleus- Prokaryotic = Absent, Eukaryotic = Present

• Cell size - Prokaryotic = Small, Eukaryotic = Large

• DNA - Prokaryotic = Naked, Eukaryotic = Linear

• Organelles - Prokaryotic = No membrane bound, Eukaryotic = Membrane bound

• Ribosome - Prokaryotic = 70s, Eukaryotic = 80S

• Cell division - Prokaryotic = Binary fusion, Eukaryotic = Mitosis/meiosis

• Examples - Prokaryotic = Bacteria, Eukaryotic = Fungi

Function of smooth endoplasmic reticulum?

Synthesize lipids

Function of Golgi apparatus?

Sorting and packing protein and lipids for secretion and delivery to other organelles

Function of vesicles?

Metablosim, buycony, Enzyme storage

Function of vacuoles?

Homeostasis, storage and structural support

Function of lysosomes?

Breaking down waste and foreign materail

Common processes carried out by all life?

• Metabolism

• Homeostasis

• Excretion

• Growth

• Nutrition

• Movement

• Reproduction

• Response to stimuli

How does Paramecium preform the function of life ?

• Metabolism: Metabolic pathways occur in the cytoplasm.

• Response: Cilia allow movement toward/away from stimuli (chemotaxis).

• Homeostasis: Contractile vacuoles pump out excess water that enters by osmosis.

• Growth: Consumes food to increase size.

• Reproduction: Asexual (binary fission) or sexual (conjugation).

• Excretion: Waste exits by diffusion; solid waste via an anal pore.

• Nutrition: Engulfs bacteria/algae via cytostome and digests them in food vacuoles.

Chlamydomonas?

• Nutrition: Autotrophic (photosynthesis) but can be heterotrophic in the dark.

• Metabolism: Enzymes in the cytoplasm catalyze metabolic reactions.

• Response: Phototactic; the eyespot detects light, and flagella move the cell toward it for photosynthesis.

• Homeostasis: Contractile vacuoles remove excess water, maintaining internal balance.

• Reproduction: Asexual (mitosis/zoospores) or sexual (fusion of gametes/isogamy).

Atypical cells?

Eukaryotic cells that challenge the cell theory

Compare and contrast plant animal and fungi cells?

• Cell wall - Animal=NO, Plant=YES, Fungi=Yes

• Chloroplast - Animal=No, Plant=YES, Fungi=NO

• Vacuole - Animal=SMALL/NONE, Plant=LARGE, Fungi=PRESENT

• Centrioles - Animal=PRESENT, Plant=Absent, Fungi=ABSENT

• Plastids- Animal=ABSENT, Plant=PRESENT, Fungi=NO

Examples of Atypical cells

• Skeletal muscles

• Aseptae fungal Hyphae

• Red blood cells

• Phloem sieve tube Elements

Explain how a Skeletal muscle cells are atypical?

They are formed by many cells fused together so have many nuclei when cells usually have one

Explain how asptate fungal hyphae cells are atypical?

They are long tube like structure without internal cross wall with many nuceli and a cytoplasm connecting (normally divided into seperate cells)

Explain how a red blood cells are atypical?

They are specialized for oxygen transport and have no nucleus

Explain how phloem sieve tube elements are atypical?

They are a long tube connected end to end with pores between cells(sieve plate) and have no nucleus

What imapct gene expression in an embryo?

Chemical signalling

Stem cells?

Undifferentiated cells that can divide endlessness and become specialised

Two properties of stem cells?

• Can divide to create more cells

• Differentiate to become specialized

Stem cell niche?

Where stem cells are kept inactive or promote proliferation and differentiation

Location and function of two type of multipotent stem cells in adults?

• Bone marrow

• Hair follicles

Totipotent?

Can become any cell including placenta

Pluripotent?

Can become any body cell but not placenta

Multi-potent?

partially differentiated and can become multiple related cells

Why are pluripotent cells most prevalent in embryonic development?

Because they are designed to form all specialised tissue in the body

How do you calculate surface area to volume ratio?

surface area/volume. (6a²/a³)

How does cell size relate to specialised function?

Cells specific shapes and sizes maximise their ability to preforms specialised functions

Example of cell size and specialization?

• Sperm cell

• Egg cell

• Red blood cells

• White blood cells

Differention?

The process where unspecialised stem cells become specialised

Function of the cell membrane?

To separate the cells internal and external enviroment

Advantage of membrane forming barriers within a cell?

• Compartmentalization

• Selective permeability

• Maintained internal gradients

• Increased surface area

• Protection

Locations of lipid bilayers in cells?

Plasma membrane

Simple diffusion

Passive non selective movement of non polar particles down a concentration gradient

Why does the hydrophobic core of a lipid bilayer forms a barrier to hydrophilic particles?

How can rate of diffusion be impacted?

Size of particles

Temperature

Distance

Surface area

Channel proteins?

A type of integral protein the facilitates passive transport of ions

Facilitated diffusion?

A passive selective movement allowing large polar or charged molecules to move across the cell membrane down a concentration gradient

Outlien the specificity of channel proteins for ions?

Structure and function of pump proteins?

Globular integral membrane proteins that perform active transport and move ions across a concentration gradient

What factors affect passage through the llipid bilayer?

• Small

• Hydrophobic

Glycoproteins?

Protein with charboydrate involved in cell recogniton and cell adhesion

Glyoclipids

Lipids with charbohydrate involved in cell recognition and cell adhesion

Cell membrane?

Fluid semi permeable phospholipid bilayer that separates cells interior from its environment

Amphipathic?

The hydrophilic heads and hydrophobic tails of the phospholipid bilayer

Active transpot?

Active selective movement of molecules against the concentration gradient using pump proteins

Solvation?

The process where water surround and stabilises polar or ionic solute molecule using hydrogen bonds

Oultine solvation of hydrophilic and hydrophobic substances?

Hydrophilic substance are polar or charged dissolving in water

Hydrophobic substances are non polar preventing interaction

How is water able to dissolve charged and polar molecules?

Oxygen atoms carry partial negative charges and hydrogen carries partial positive allowing water to form hydrogen bond and hydration cells breaking ionic bonds

Osmolarity?

The total solute concentration affecting water movement in and out of a cell

Isotonic?

Equal solute concentration

Hypotonic?

Low solute concentration

Hypertonic?

High solute concentration

Osmosis?

The net movement of water from a hypotonic solution to a hypertonic solution through a semipermeable membrane

Unit for concentration of a solute?

Molarity

Outline the net movement of water between hypotonic, hypertonic and isotonic solutions?

• Hypotonic = Water flows in because the solvent is more outside

• Hypertonic = Water flows out because the solvent is more inside

• Isotonic = No net flows

What happens to cells when placed in hypotonic and hypertonic solutions?

• Hypotonic = Cells swell

• Hypertonic = Cell shrinks

Effect of hypertonic and hypotonic solutions on cells with a cells walls?

Hypotonic = Turgid (Healthy state)

Hypertonic = Plasmolysis (Plasma membrane pulls away from the cell wall)

Why is tissue fluid in multicelluar organisms isotonic?

It ensure that the cells don’t shrink or change when using IV drips

Role of the contractile vacuole in freshwater organisms?

Freshwater environments are hypotonic so water constantly enters by osmosis but contractile vacuoles collect excess water and expell it from the cell

Explain the effects of hypertonic and hypotonic solutions on cells without a cell wall?

Hypotonic = Lysis (cell swells and bursts)

Hypertonic = Crenation (Cell shrinks)

Outline the use of normal saline?

Hydration shell?

A layer of water molecules that surround and bind to solute participle

Aquoporns?

Alter the permeability of the membrane

Organelle?

A discrete structure within a cell adapted to preform one or more specific function

Examples of organelles?

• Nucleus

• Ribososmes

• Mitochondria

• Golgi apparatus

Why are the cell wall cytoskeleton and cytoplasm not organelles?

They are not enclosed (lack a discrete mebrane bound structure)

Benefits of compartmentalization in the nucelus?

• Gene transcription and gene translation are separated (post-transcriptional modification)

• Genetic material is protected

Compartmentalization?

The seperation of eukaryotic cell iinteriors into distinict mebrane bound organelles

Advanatages of compartmentalization?

• Concentration of metabolites

• Maintains optimal conditions for enzymes

• Large membrane surface area

• Containment of damaging substances

Compare inititation of transcription and translation between prokaryotic and eukaryotic cells?

In prokaryotic cells, transcription and translation are not separated due to a lack of compartmentalization, so mRNA is not transported and protein production happens faster with minimal organelle involvement

Outline why post transcriptional modification of RNA is not possible?

In prokaryotes there is no nucleus so transcription and translation are coupled so mRNA is translated imediatley

Post transcriptional modification?

The process by which newly made RNA is chemically and structurally changed after transcription before translation (prokaryotes cant do this)