Cells

Question 1

what is the smooth endoplasmic reticulum?

Answer 1

it does not have ribosomes attached and it synthesises and processes lipids

Question 2

what is the rough endoplasmic reticulum?

Answer 2

it has ribosomes attached onto it. the rough er processes these proteins

Question 3

what is the nucleus?

Answer 3

the nucleus is genetic information from chromatids which are kept in a nuclear envelope. the nucleus also has a nucleolus inside

Question 4

what is the function of the cell surface membrane?

Answer 4

to control the movement of substances in and out of the cell

Question 5

describe the structure of mitochondria.

Answer 5

it has a double membrane and has cristae that allows for more surface area. inside this structure is a matrix which contains all the enzymes needed for respiration inside it

Question 6

describe the function of ribosomes

Answer 6

protein synthesis

Question 7

what is the function of the golgi apparatus?

Answer 7

processes and packages proteins made in the rougher and the cytoplasm. then expels them out so they can bind to the plasma membrane in a process called exocytosis

Question 8

what is a golgi vesicle?

Answer 8

a fluid-filled sac in the cytoplasm, surrounded by a membrane and produced by the golgi apparatus

Question 9

describe the structure of a chloroplast?

Answer 9

a double membrane surrounding a dense fluid called the stroma and elaborate membrane system called thylakoids, enclosing the thylakoids space. Thylakoid sacs may be stacked to form grana. chlorophyll is embedded in the thylakoid membrane.

Question 10

describe the structure and function of lysosomes

Answer 10

contains digestive enzymes which are called lysosymes. they are kept separate from the cytoplasm

Question 11

what is the cytoplasm?

Answer 11

fluid inside the cell where chemical reactions take place

Question 12

describe the cell wall

Answer 12

in fungi its made of chitin and in plants and algae its made of cellulose. it keeps the cell’s structure rigid

Question 13

describe the differences between a prokaryote and a eukaryote

Answer 13

cytoplasm that lacks membrane-bound organelles
smaller ribosomes
no nucleus; instead they have a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins
a cell wall that contains murein, a glycoprotein.

Question 14

describe the structure of a virus

Answer 14

attachment proteins to allow the virus to attach to the cell it is going to affect
capsid - a protein coat to surround the RNA/DNA
envelope - to protect the RNA/DNA but only present in some viruses

Question 15

mm to micrometers

Answer 15

x1000

Question 16

micrometers to nanometers

Answer 16

x1000

Question 17

features of a optical microscope

Answer 17

light to form an image
objects larger than 0.2 micrometers
colour
live
max magnification is x1500

Question 18

features of an electron microscope

Answer 18

electrons to form an image
black and white
dead
much smaller objects can be seen because electrons have a shorter wavelength than light
max magnification is x1.5 million

Question 19

what is the definition of resolution

Answer 19

the ability to distinguish between two points

Question 20

TEM advantages

Answer 20

high resolution
v small objects can be seen

Question 21

TEM disadvantages

Answer 21

needs to have a thin specimen
dead samples
artefacts may get in the way of seeing the specimen

Question 22

SEM advantages

Answer 22

can be used on 3D samples

Question 23

SEM disadvantages

Answer 23

lower resolution than TEM
sample has to be dead

Question 24

how do electron microscopes work?

Answer 24

using a beam of electrons which are focused by magnetic fields, an image of a specimen is formed

Question 25

magnification equals

Answer 25

image/object

Question 26

what do you need to do to look at individual organelles?

Answer 26

a process called ultracentrifugation

Question 27

what is the process of cell fractionation?

Answer 27

1. homogenation - breaking up the cells with a blender, vibration or using a detergent 2. filtration - remove the large unwanted bits like the cell membrane etc 3. ultracentrifugation - spun into centrifuge so components seperate out by weight (heavier ones at the bottom. supnatant removed and spun again at a higher speed

Question 28

what happens when phospholipids are shaken with water?

Answer 28

they form micelles

Question 29

what are the three types of lipid found in the bilayer?

Answer 29

cholesterol glycolipids phospholipids

Question 30

what are the two types of proteins found in the bilayer?

Answer 30

glycoproteins other proteins eg. transport proteins

Question 31

what is the function of the phospholipid bilayer?

Answer 31

to act as a barrier between the cytoplasm and substances outside the cell. to make sure that only lipid soluble, non polar and small substances can pass through the membrane can be chemically modified to act as signaling molecules by: moving within the bilayer to activate other molecules (eg. enzymes)

Question 32

what is the function of cholesterol in the plasma membrane?

Answer 32

increases the fluidity of the membrane and stops it from becoming too rigid at low temperatures. to make sure that the phospholipid tails are too closely packed together cholesterol and phospholipid tails also stabilises the cell membrane at higher temperatures by stopping the membrane from becoming too fluid contribute to the impermeability of the membrane to ions increases mechanical strength and stability of membranes

Question 33

what is the function of glycolipids and proteins in the cell membrane?

Answer 33

signalling receptors for hormones and neurotransmitters receptors involved in endocytosis receptors involved in cell adhesion and stabilisation they act as receptor molecules allows glycolipids and glycoproteins to bind with certain substances at the cell's surface cell markers or antigens, for cell-to-cell recognition

Question 34

what's the function of proteins in the cell membrane?

Answer 34

transport proteins create hydrophilic channels to allow ions and polar molecules to travel through the membrane. there are two types: channel (pore) proteins, carrier proteins each transport protein is specific to a particular ion or molecule transport proteins allow the cell to control which substances enter or leave

Question 35

how does temp affect membrane permeability?

Answer 35

when temp increases, phospholipids begin to have more kinetic energy so begin to move more. makes membrane more fluid. if temp continues to increase eventually will break down completely. loss of structure increases permeability also carrier and channel proteins will also be denatured at high temps. these are affected in transport do as they denature permeability will also be affected

Question 36

how does ph affect membrane permeability?

Answer 36

as the pH got higher the absorbance of light got lower. We concluded that high pH makes cell membranes become less permeable, allowing less molecules to pass through.

Question 37

what is simple diffusion?

Answer 37

molecules pass directly through the plasma membrane without the assistance of another molecule

Question 38

what is facilitated diffusion?

Answer 38

the passive movement of a particle across a cell membrane via a channel protein.

Question 39

what are the factors that affect diffusion?

Answer 39

temperature concentration gradient steepness the properties of the molecule diffusing SA

Question 40

describe the process of active transport?

Answer 40

1) molecule binds to receptors in carrier protein on outside 2) ATP binds to carrier on inside 3) ATP hydrolyzed to form ADP and phosphate 4) energy is released 5) phosphate changes shape of carrier

Question 41

what is active transport prevalent in?

Answer 41

reabsorption of useful molecules and ions into the blood after filtration into the kidney tubules absorption of some products of digestion from the digestive tract loading sugar from the photosynthesising cells of leaves into the phloem tissue for transport around the plant loading inorganic ions from the soil into root hairs

Question 42

structure of HIV

Answer 42

structure of HIV: Its inner core consists of a protein capsid enclosing two molecules of RNA, two molecules of an enzyme called reverse transcriptase, and a few other enzyme molecules. The capsid is enclosed in another layer of viral protein, the matrix. External to this is a viral envelope composed of phospholipids and glycoproteins derived from the host cell.