Uplearn Bio Stuff

that blew my mind or were just helpful

how to find the actual length of something on a microscope

number of units on the eyepiece graticule x magnification factor

how can the magnification factor be found

find the largest possible number of units of micrometres that line up nicely with each other and do:

micrometres/eyepiece graticule units

formula for magnification

size of image/size of real object

what is magnification

how many times bigger an image viewed through a microscope is compared to the real object

what is resolution

the ability of a microscope to distinguish between two objects that are very close together

advantages %%electron%% microscopes have over light microscopes

* better magnification
* better resolution
* 3D or internal imaging

advantages light microscopes have over %%electron%% microscopes

* better portability
* can view living specimens
* colour images

what do %%electron%% and light microscopes have in common

* thick sample sections
* easier sample preparation
* reduced risk of artefacts

what are artefacts

objects that can appear under a microscope that are not part of a sample

what are examples of artefacts

* air bubbles
* fingerprints
* dust

what are artefacts most common in

%%electron%% microscopes

what is cohesion

When the positively charged hydrogen atom of one water molecule is attracted to the negatively charged oxygen atom of another water molecule, forming a hydrogen bond.

what is adhesion

When water molecules are attracted to the impermeable walls of xylem tissue.

define hydrophilic

soluble in water

define hydrophobic

insoluble in water

What is a dipolar molecule?

a molecule that has equal and opposite charges at both ends

go back to uplearn

recall quiz monosaccharides

What is cellulose?

A polysaccharide formed by condensation of **beta glucose** , containing only **1** , **4** -glycosidic bonds.

What is starch?

A polysaccharide formed by condensation of **alpha glucose.**

What is glycogen?

A polysaccharide formed by condensation of **alpha glucose,** containing **1,4- and 1,6- glycosidic bonds.**

Starch and glycogen are insoluble in water. Why does this make them good storage molecules?

It means they don’t affect the **water potential** of the cell.

Starch and glycogen are coiled. Why does this make them good storage molecules?

It makes the molecules **compact** .

Starch and glycogen are branched. Why does this make them good storage molecules?

It means there are more ends for fast breakdown

Starch and glycogen are polymers of glucose. Why does this make them good storage molecules?

It means they provide glucose for respiration

Starch and glycogen are large molecules. Why does this make them good storage molecules?

It means they can’t cross the cell-surface membrane

What is a triglyceride?

A molecule formed by condensation, with **ester** bonds joining **three fatty acids** to one molecule of **glycerol**

What is a phospholipid?

A molecule formed by condensation, with two fatty acids and a phosphate group bonded to one molecule of glycerol.

What is a conjugated protein?

A protein that contains **non-protein prosthetic groups**, attached by **covalent, ionic or hydrogen** bonds.

groups bounded to the central carbon atom of an amino acid

* carboxyl group
* amine group
* hydrogen atom
* R group

What is a protein’s secondary structure?

The particular folding of a chain of amino acids in the polypeptide(s) of a protein.

What is a protein’s tertiary structure?

The particular folding of a whole polypeptide chain, as determined by the amino acids that make up the polypeptide

What is a protein’s quaternary structure?

A number of polypeptide chains linked together, and sometimes associated with non-protein groups, to form a protein

What is an enzyme?

A protein or RNA molecule that acts as a catalyst, increasing the rate of a biochemical reaction by lowering the activation energy

What is an active site?

In an enzyme, the group of amino acids that make up the region where a substrate fits to catalyse a reaction.

Why is the tertiary structure of enzymes important?

The active site has a specific tertiary structure which is complementary to a specific substrate, enabling an enzyme-substrate complex.

In the context of enzymes, what is a substrate?

A substance that is acted on or **used** by another substance or process.

What is DNA?

A molecule with a/an **double** helix structure which consists of hydrogen bonds between specific **complementary** base pairs on two **antiparallel** polynucleotide chains. \n \n DNA carries the **genetic** code for the production of **proteins or protein or polypeptides** .

What is a nucleic acid?

Molecule that carries the genetic code for the production of proteins.

What is the nuclear envelope?

A **double** membrane surrounding the **nucleus** , which controls entry and **exit** of materials

What are cristae?

Folds in the **inner** membrane of the **mitochondria or mitochondrion** . They are the site of **oxidative** **phosphorylation** .

What is the rough endoplasmic reticulum?

System of **membranes** that is continuous with the nucleus, with **ribosomes** on the outer surface. Site of **synthesis** and **transportation** of proteins & **glycoproteins** .

How does the structure of the rough endoplasmic reticulum help enable synthesis of proteins?

The rough endoplasmic reticulum has **ribosomes** and a large **surface area**

What is the smooth endoplasmic reticulum?

System of membranes with no ribosomes on the outer surface. \n \n Site of synthesis, storage and transportation of lipids and carbohydrates.

What are the 4​ functions of the Golgi apparatus?

* *Produces secretory enzymes and carbohydrates.*
* *Stores and modifies proteins & triglycerides.*
* *​Forms vesicles for transporting proteins/triglycerides.*
* *Forms lysosomes.*

What is a lysosome?

A lysosome is a **membrane bound** organelle that releases **hydrolytic** enzymes.

What is the function of ATP?

An **immediate or very fast or very quick** source of **energy** for biochemical processes and **synthesis** of biological molecules.

How does the structure of ATP make it a good source of immediate energy?

The bonds between the phosphate groups have a low **activation energy** . This means they can be easily **broken** . Breaking the bonds releases **energy**

Define active transport.

Active transport is the movement of molecules from a region of **low** concentration to **high** concentration, using carrier proteins and energy from the **hydrolysis** of ATP.

What are thylakoids?

Flattened **sacs** in the chloroplast, containing **chlorophyll** . \n Site of the **light** - **dependent** reaction for **photosynthesis**

What is the stroma?

The stroma is the **matrix** of the **chloroplast** in a plant cell. \n Site of the **light** - **independent** reaction for **photosynthesis** .

What are grana?

Stacks of thylakloids found in the chloroplast

What is the function of the plant cell wall?

Provides **rigidity or integrity** to the cell and stops the cell from bursting by exerting inward pressure to prevent **osmosis** . \n \n This enables **turgidity** which makes parts of the plant semi-rigid

What is a vacuole?

A fluid-filled **sac** with a **single** membrane.

What is the function of the vacuole in a plant cell?

* It supports the plant by making cells **turgid** .

\
* Stores **sugars** and amino acids which can act as a temporary food storage.

\
* In **petal** cells, it can store **pigments** to attract pollinating insects.

State three purposes of mitosis.

Mitosis is needed for

* growth
* repair
* asexual reproduction.

State two purposes of meiosis.

Meiosis is needed for

* production of haploid cells for sexual reproduction.
* It helps ensure genetic variation.

Define mitosis in terms of the daughter cells produced.

* The cell divides **once** to produce **two or 2 or pair of** daughter cells. \n
* Each daughter cell has a/an **identical** **copy** of the DNA produced by the parent cell during replication.

Define meiosis in terms of the daughter cells produced.

* The cell divides twice to produce four daughter cells. \n
* Each daughter cell is genetically different.

What is the function of the phospholipid bilayer?

* Allows diffusion of **lipid** soluble substances.

\
* Prevents movement of **water** soluble substances.

What are the two functions of cholesterol embedded in the cell membrane?

* Reduce **fluidity or permeability** and **fluidity or permeability** of the cell membrane.

\
* Increase **rigidity** of the cell membrane.

What is a glycoprotein?

A protein attached to a **carbohydrate** chain on the **cell-surface membrane**

What are the two functions of a glycoprotein?

* Acts as a recognition site for **hormones or neurotransmitters** and other cells. \n ​
* Helps cells attach together to form **tissues or tissue** .

$$​

\n

Define simple diffusion.

A **passive** method of transport across the cell **membrane or membranes** via the **phospholipid bilayer**

Define facilitated diffusion.

A passive method of transport across membranes involving carrier proteins and channel proteins

What type(s) of transport are carrier proteins involved in?

* facilitated diffusion across the cell membrane.
* active transport across the cell membrane.

What type(s) of transport are protein channels involved in?

facilitated diffusion across the cell membrane

What is the term used to define the response of T cells to a foreign antigen?

**Cell** - **mediated** immunity.

Define humoral immunity.

Humoral immunity is the

* response of B lymphocytes to a foreign antigen
* clonal selection
* the release of monoclonal antibodies.

How does the secondary immune response differ from the primary immune response?

In the secondary immune response, plasma cells and antibodies are produced at higher speed and concentration as a result of memory cells produced during the primary immune response.

What is an antibody?

A **protein** produced by **B** lymphocytes in response to the presence of a specific **antigen** .

What are monoclonal antibodies?

Antibodies with the same **tertiary** structure, produced from cloned **B-cells**

Describe active immunity.

Resistance that arises as a result of exposure to a/an **antigen** , which causing B lymphocytes to produce **antibodies**

Define passive immunity.

Resistance that arises when **antibodies** introduced into the body (either from injection or breastfeeding) bind to and **destroy** specific toxins/venoms/antigens.

Insect tracheoles have thin walls. How does this increase the efficiency of gas exchange?

It means there is a short diffusion distance to cells.

Insects have a large number of highly branched tracheoles. How does this increase the efficiency of gas exchange?

It means there is a short diffusion distance to cells and a large surface area for gas exchange.

Insect tracheae are full of air. How does this increase the efficiency of gas exchange?

It means that gases diffuse quickly into tissues.

Fluid in the ends of tracheoles moves out into tissues during exercise. How does this increase the efficiency of gas exchange?

The final diffusion pathway is gas rather than liquid, so

* diffusion to the gas exchange surface is faster
* surface area for gas exchange is larger.

Insects can use their muscles to move air through tracheae. How does this increase the efficiency of gas exchange?

Maintains a steep diffusion gradient for oxygen and carbon dioxide.

what are the three stages of cell fractionation

* homogenisation
* filtration
* ultracentrifugation

what is homogenisation

breaking up the cells in a tissue sample

what is filtration

removes large cell debris or unbroken cells

what is ultracentrifugation

seperates cell organelles by mass

what are the conditions for homogenisation

tissue sample is placed in a

* ice cold


* buffered
* isotonic

solution

why is the homogenisation solution ice cold

to prevent enzyme activity that breaks down organelles

why is the homogenisation solution buffered

to prevent proteins/enzymes from denaturing

why is the homogenisation solution isotonic

to prevent osmosis which could cause organelles to burst

what happens during homogenisation

* the tissue sample is placed in the solution
* then it is blended
* this releases the cell organelles into the tissues

what happens during ultracentrifugation

* the filtered solution is pipetted into a tube and put in the centrifuge
* it is spun at a low speed, causing the organelles with the greatest mass (nuclei) to form a pellet at the bottom of the tube
* the pellet remains in this tube and the supernatent is pipetted into another tube and is put into the centrifuge
* spun at a slightly higher speed
* repeated until desired organelle is found in the pellet

what do molecules that cross the phospholipid bilayer have to be

* non-polar
* uncharged
* hydrophobic

role of lipids in the phospholipid bilayer: phospholipids

* regulates membrane fluidity by

\
* restricting the movement of phospholipids/proteins
* prevents water/ions from leaking out of the cell

role of lipids in the phospholipid bilayer: phospholipids

* control movement of substances by only allowing

\
* uncharged
* non-polar
* hydrophobic

\
substances across

role of lipids in the phospholipid bilayer: glycolipids

* act as recognition site for other cells
* which allows cells to attach to one another to form tissues

role of proteins in the phospholipid bilayer: on membrane surface: surface proteins

* found on the upper or lower membrane surface of the phospholipid bilayer
* provide mechanical support for the membrane

role of proteins in the phospholipid bilayer: on membrane surface: glycoproteins

either act as

* recocgnition sites for foreign cells
* recognition sites for specific chemicals so that specific hormones outside the cell can trigger a response inside the cell

role of proteins in the phospholipid bilayer: span the membrane: transport proteins

* help transport substances across the membrane

what is the phospholipid bilayer nicknamed and why

* the fluid-mosaic model
* fluid: phospholipids and some proteins can move in their layer of the membrane
* mosaic: describes the random scattering of proteins

what are Pathogens

any microorganism that causes disease.

State the four types of non-self cells that lymphocytes can recognise.

* pathogen
* toxin
* abnormal/cancer/tumour
* human

what is an antigen

An antigen is a protein in the cell surface membrane that triggers an immune response.

How are Lymphocytes able to recognise antigens

because they have **receptors** that are **complementary** to **antigens** on non-self cells.