Biology EOY

Unicellular

single cell

multicellular

many cells

cell

functional unit of life in which chemical reactions that maintain life takes place within

What is a eukaryote and what cells are they?

• true nucleus

• plants, animals

• has true nucleus containing genetic material [DNA] enclosed within the nuclear envelope

What is a prokaryote and what cells are they?

• before the nucleus

• bacteria, archaea

• lacks true nucleus → genetic material lies freely in cytoplasm

Size comparisons

Three major structural features that make up the protoplasm of a cell

1. cell surface membrane

2. nucleus

3. cytoplasm

Protoplasm

cell living matter

What’s inside the cytoplasm of a cell

1. cytosol

2. organelles

3. cytoskeleton

cytosol

fluid component, aqueous solution of essential ions [soluble organic compounds like sugar and amino acids; soluble proteins like enzymes]

cytoskeleton

network of fine strands of globular proteins, support cell and maintain overall shape

ultrastructure

structure of cells

organelles

compartments in cytoplasm, might have membrane, has its own function, specific chemical reactions within each

which organelles are double membrane?

nucleus, mitochondria, chloroplast = double membrane

ribosomes have _____ membrane

no membrane

Which organelles are single membrane

lysosomes, vacuole = single membrane

Similarities of plant cell and animal cell (4)

• Cell surface membrane

• Nucleus

• Cytoplasm with ER, GA, mitochondria, ribosomes

• Chromosomes composed of linear DNA wound around proteins

Differences between plant cell and animal cell (5)

cell wall, lysosome, vacuole, chloroplast, centriole

Nucleus structure

• Spherical or ovoid

• Double-membrane known as nuclear envelope
  > outer – continuous with ER
  > inner – in contact with nucleus contents

• nuclear envelope has pores → nuclear pores

• contains nearly all cell’s DNA (organised into chromosomes)

• one or more nucleolus within nucleoplasm

nucleus functions (4)

• controlling cellular activities

• regulate protein + enzyme synthesis

• nuclear division (basis of cell replication)

• nucleolus — synthesis and partial assembly of ribosomes

what does the nucleolus do

synthesis and partial assembly of ribosomes

nuclear division

basis of cell replication

cell surface membrane structure

• phospholipid bilayer

•  hydrophobic tails on interior

• hydrophilic heads on exterior

What is a phospholipid made up of?

Phospholipid is made up of
> glycerol molecule attached to a phosphate group and 2 fatty acid chains

Additional components in cell surface membrane

• cholesterol

• glycoproteins

• glycolipids

• transport proteins

cell surface membrane function

• partially permeable membrane which acts as a barrier between cytoplasm and environment

• prevents most water-soluble substances from entering/leaving

ribosome structure

• no membranes

• 2 subunits – large subunit and small subunit

Where can ribosomes be found in a eukaryotic cell?

• Found attached to the rER

• Found as free ribosomes in cytosol

what are ribosomes made up of?

Made up of protein and ribonucleic acid (ribosomal RNA)

ribosome function

protein synthesis

Endoplasmic reticulum (ER) structure
Where does ER originate from and consist of?

• Originates from outer membrane of nuclear envelope

• Consists of a network of membranous tubes/sacs called cisternae

• Rough ER (rER)

• Smooth ER (sER)

Cisternae

a network of membranous tubes/sacs in ER

a stack of flattened membrane-bound sacs in GA

Difference between rough ER structure and smooth ER structure

• rER has ribosomes present while sER lacks ribosomes.

• sER are more tubular.

rER function

protein synthesis

sER function

lipid synthesis

What does the golgi apparatus consist of? Tell me about its structure.

• Consists of a stack of flattened membrane-bound sacs called cisternae

• Continually being formed at cisface by vesicle fusion from ER

• Continually budded off at trans face where vesicles are pinched off

GA function

• Chemically modifies, sorts and transports molecules

• Lysosome formation

Mitochondria structure/shape

• Rod-shaped or cylindrical-shaped organelle

• Double membrane separated by intermembrane space
  > outer membrane - smooth, continuous boundary
  > inner membrane - extensively folded to form cristae which project into the interior (matrix)

• The matrix contain hereditary materials [circular DNA, RNA] and ribosomes

What is the double membrane in a mitochondria separated by?

intermembrane space

Compare the inner and outer membrane of a mitochondria.

• outer membrane - smooth, continuous boundary

• inner membrane - extensively folded to form cristae which project into the interior (matrix)

What does the matrix of a mitochondria contain?

• hereditary materials (circular DNA, RNA)

• ribosomes

mitochondria function

cellular respiration → to release energy

Lysosome structure

small, spherical vesicles

Lysosomes are formed by _____

Golgi Apparatus

GA apparatus forms ____

lysosomes

Lysosomes are ____ in plants

larger

Lysosomes contain __________________________

hydrolytic digestive enzymes

Lysosome function

• Digestion of materials taken in by cells (during endocytosis and exocytosis)

• Autophagy

• Autolysis

Autophagy

digestion of worn-out/improperly functioning organelles

Autolysis

self digestion of a cell by release of lysosome contents within cell

Differences of vacuoles in animal cells and plant cells

• In an animal cell → small, less permanent and are called vesicles

• In a plant → large, central, permanent and surrounded by a membrane (tonoplast) which contains cell sap

vacuole structure

Fluid-filled structures bound by single membrane

Vacuole functions

• Water entry

• Cell expansion during cell growth

• Contains pigments [anthocyanins]

• Hydrolytic enzymes make vacuoles act as lysosome

• Stores waste products

• Stores food

Vacuoles contain _____ called ________

pigments called anthocyanins

What makes vacuoles act like lysosomes?

hydrolytic digestive enzymes

centriole structure

Cylindrical (tube-like) structure

What are centrioles composed of?

microtubules

What does 1 centriole consist of?

• 1 centriole consists of 9 microtubule triplets arranged as a cylinder

How many centrioles make up a centrosome?

2 centrioles = 1 centrosome

How can centrioles be found?

• Found in pairs in cytoplasm, outside nucleus but close to it

• Found as single structures at the base of cilia and flagella

centriole function

• Produce spindle fibres which attach to chromosomes and separates them during cell division

• Formation of cilia and flagella

Chloroplast structure

• Large

• Double membrane — outer, inner

Compare the outer and inner membrane of chloroplasts

• outer — smooth, continuous

• inner — give rise to lamellae or thylakoids which extends through interior

What is in the interior of a chloroplast?

• Interior is a gel-like matrix called stroma

stroma

gel-like matrix in interior of chloroplast

what happens in stroma/chloroplast interior?

• In stroma, thylakoids are stacked into grana, which are joined together by intergranal lamellae

What does chloroplast contain?

Contains chlorophyll which make chloroplasts appear green

chloroplast function

photosynthesis

cell wall structure of plant cells

• Surrounds plant cells, external to cell surface membrane

• Made of cellulose

• Strong yet permeable materials

• Allowing free passage of substances in and out of cell

cell wall function

• Mechanical support

• Protective layer

What are the two methods of protein synthesis?

• Proteins secreted out of the cell (extracellular) → Protein secretory pathway

• Proteins needed within the cell → Synthesised by free ribosomes

Protein secretory pathway (8)

1. Ribosome bound to rER synthesise the polypeptide chain into the rER

2. Protein becomes enclosed in an ER/transport vesicle

3. ER vesicle containing the protein bud off from the ER

4. The vesicle travels and fuses with the cis-face of the GA

5. The GA chemically modifies, sorts and transports the proteins

6. The proteins move through the GA by Golgi vesicles budding off from one cisterna and fusing with another

7. The secretory vesicle containing the protein buds off from the trans-face of the GA, travels and fuses with the cell surface membrane

8. The protein is released out of the cell

Which elements does carbohydrate contain?

• Carbon, hydrogen, oxygen

• C_x(H₂O)_y

Three different forms of carbohydrates

• monosaccharide

• disaccharide

• polyscaccharide

Hexose sugars

Glucose, fructose, galactose

monosaccharide definition

• Carbohydrates which cannot be hydrolysed to simpler carbohydrates

• (CH₂O)_n

Disaccharide definition

How are disaccharides formed?

Formed by a condensation reaction between two monosaccharides, one molecule of water is removed from the pair of monosaccharides

Glycosidic bond

bond formed between 2 monosaccharides

Glucose + Glucose

Maltose

Disaccharide examples

• Maltose = glucose + glucose

• Lactose = glucose + galactose

• Sucrose = glucose + fructose

Glucose + Galactose

Lactose

Glucose + Fructose

Sucrose

Polysaccharide definition

Polymers of monosaccharides

Examples of polysaccharides

• starch

• glycogen

• cellulose

What is starch used for?

storage in plants

What is glycogen used for?

storage in humans

What is cellulose used for?

structural in plants

Starch is a polymer of _____

glucose

Starch’s structure

Amylose and Amylopectin

Amylose structure

> straight chain structure with a helical structure for more compact structure
> several thousand glucose units joined by glycosidic bonds

Amylopectin structure

> compact
> highly branched structure
> glucose units within and between branches are held together by glycosidic bonds
> has two times glucose units than amylose

Functions of carbohydrates (5)

• source of energy

• sucrose → good transport sugar in phloem of plants

• polysaccharides like starch, glycogen → good storage molecules

• cellulose → good structural polysaccharides

• monosaccharides → synthesise nucleic acids (deoxyribose, ribose), disaccharides, polysaccharides

Why is sucrose a good transport sugar in plant phloem?

• very soluble → can be moved in high concentrations

• chemically unreactive

Why are some polysaccharides like starch and glycogen, good storage molecules?

• large

• insoluble

• indiffusible through partially permeable membrane

• compact shapes → allow more carbohydrates to be stored

• easily hydrolysed into monosaccharides

Why is cellulose a good structural polysaccharide in plants?

• Found in all cell walls → good cell wall material

• Good tensile strength

• Permeable to water and solutes

deoxyribose

constituent of DNA

ribose

constituent of RNA

Which carbohydrates are reducing sugars?

Monosaccharides, Lactose, Maltose

How does Benedict’s test work?

• Benedict’s test – sugars can reduce copper from valency 2 to 1

• Alkaline copper (II) sulphate (CuSO₄) → reduced to → insoluble copper (I) oxide (Cu₂O) [a brick red precipitate]

• Cu²⁺ (blue solution) + e^- → Cu⁺ (brick-red precipitate)

Reducing Sugar Procedure (4)

• To 2 cm³ of the sample, add an equal volume of Benedict’s solution

• Mix well

• Place the test tube in boiling water bath for 2 minutes

• Observe colour changes